Hi welcome to Tear Down! Tuesday Yes, we're going to take a look at a bit of historic gear here. I've done a previous video on this a tour of the old analog TV transmission facility at Artaman here in Sydney and I scored this gear which was the actual gear used in the rack to transmit the channel 7 TV signal over most parts or a good lot of Sydney here. So really historic bit of gear and they switched it off. Of course, they moved entirely to digital and this is the original gear that transmited made in around 1981 and it's been in use since then.

Not uh, continuously, but because it gets switched in with uh backup gear and rotated through other gear. But this gear itself has, you know, a couple hundred th000 hours use out of it. So um, you know, really well used gear and built like a brick dny it really is over engineered. This sort of stuff very rarely fail, so it should be a real interesting tear down.

But unfortunately I apologize up front. There's no way I can do ad Justice to this thing. It doesn't matter how I try and explain things how I tear things down. We've got the full manuals, the full theory of operation, the Uh schematics, the service manuals, the whole works for this thing.

and there's no way that I can really do it. uh, justice in depth. So unfortunately, all we're probably going to have to do is a basic overview the stuff, then we'll take it apart, have a look at the Uh construction and all. Uh, we'll might cover uh, some basic operational block diagrams and things like that, but nothing more in depth.

I'm sorry I will try and scan the Uh manuals or you know, a good lot of it anyway. Um, it could be quite an effort and I'll link those in if you really want the Uh to go into the circuit detail and exactly how it all works. But anyway, this is you know, pretty much just a tear down. Let's pop the hood on these things and see what they're like.

But the first thing we're going to check out is because this stuff is really interesting. The documentation: H Let's see what documentation was like for a bit of really uh Niche gear I mean they would have I think the serial number on this is like 200 and something like that. They wouldn't have manufactured these only in the hundreds, maybe even the low thousands or something like that worldwide over the lifetime of these actual units. so really not.

This is the exact opposite of high volume consumer stuff, really. Niche stuff made by NEC in Japan who still make a lot of the Uh TV transmitters used around the world. so they going to be really interesting, especially the documentation. the amount of work and things they put into this just to you know, um, support these products which would have cost a fortune I Don't even know the price and if you have to ask the price, you can't afford it.

So here we go. So let's take a look at the documentation. It comes in uh, two binders here and so we'll take a look at uh, volume one here cuz I don't think there's a huge amount in volume 2 that we're interested in. Um, it's the PCN 1205 ah VHF TV transmitter and this documentation is for the entire rack because this is the model number not just for any one of these bits of gear, but for the entire rack which NEC sold as a complete system and this is all of the Uh supporting documentation that went along with it.

So like I said, they had to uh, compile this and write this back in uh, the very early 80s? uh probably. uh you know, late 7s. A lot of it would have maybe been uh based on some earlier uh stuff perhaps. but this is all around about that vintage so let's take a look at it and it has all sorts of different uh sections in it for um, all of the different uh you know General overview and spect of like the rack and things like that and the overall system, how it works, protection and then we got into the maintenance operation and then we've got the individual uh modules down here which we'll take a look at.

Buto here we go I Love this death on contact look at that. You don't want to die doing this sort of stuff. Death on contact high voltage warning Will Robinson Dangerous dangerous. It looks like second edition that one's been added later CPR All that sort of stuff.

Um, because you know this is serious business I mean this? um, not the instruments we're looking at today I mean they're just, you know, regular 240 volt, um stuff. you know, a couple hundred Watts uh output things like that of the Uh Power Amplifier But in terms of the Exciter and the really, you know, high-end high power stuff in the rack that generated the couple of kilowatts. um, going into the antenna, that's the real dangerous stuff. Anyway, look at this all uh, you know all uh, type um, all done on uh typewriter.

As you can see, it's fantastic. All different sections all done and somebody's had to put that in a type riter and done it. And here we go: I Won't go through all the uh details I'll scan this as I said and you can read through it to your heart's contain. But here we go.

The PCN 1200 series is what we got. uh TV transmitters at latest if modulation type VHF TV Transmitter solid state techniques are more and more used in TV transmitter uh, solid state with solate Exciter employed concurrent with If modulation, blah blah reduce use tube usage, enhance of reliability and reduction of Maintenance costs have been realized through uh full utilization of solid state technique. So even back in the 80s here it was a big deal to switch over to Uh Solid State uh stuff. And of course the final Uh transmitter is a valve.

but uh, pretty much everything else is uh, solid uh state in this thing. So here we go: Composition: ah, use of newly de developed steel rack I Love this shaes great strength and Superior earthquake proof properties. Well hey, Japanese company is probably a big deal, you know Japan Japan is subject to earthquakes. not so much here in Australia Not a big deal, but hey, they've put thought into that that the Uh transmitters still go during a massive earthquake, natural disaster, that sort of thing.

And here's an overview of the rack with which you saw in the previous video which will be linked in. if you haven't seen it. definitely watch that first. and that's the big three door.

All of the equipment we're looking at was in this one over here and then, well, well, it'll get a breakdown. Here it is. here we go. Here's the breakdown of the actual Uh rack itself.

So we got ourselves the um, this is the gear we're going to look at. We don't have the TX control unit um I've told there's nothing really interesting there. but we start with the Uh modulation uh unit. We've got that that one's going to be a big deal.

Um, the if corrector we don't have I'm told that's you know. pretty trivial, not really. hugely. anything interesting in there.

and in a lot of cases you may actually not need the If corrector. It's um, anyway. Uh, then we've got the VHF mixer which we'll look at. Um, that won't be hugely interesting because it's just a mixer.

I mean a lot of the analog art magic for transmitting the and modulating and ensuring that the TV signal and audio as high quality is all done in the modulation unit down in here. So the mixer is just as it says, a mixer to mix the Um IF frequency up to a Um up to the carrier frequency of the transmitter. And then we've got the power amplifiers of course, separate power amplifier for audio and video as we saw. And then here is the big Power Amplifier Oh, there we go.

That one had the big uh, huge multi- kilowatt valve in there. and then we got a SN diplexer over here. and that's pretty much, um, what constitutes the Sy Tire rack system and what this documentation is all about. And they talk about the coaxial feeders of course, the Um RF coaxial, the Coolin fair, and the exhaust ducks and things like that.

woo specifications. Here we go. This is, uh, rather interesting. The unit we're actually looking at here is the PCN 125 Little pissy little 5 kilowatt unit.

Ah man. hopeless, they make them. This series went up to 25 khz. Uh, Kilz 25 kilowatt.

Um, it transmitters the carrier frequency stability. Here we go. It tells you about the Tcxo Uh, Plusus 150 HZ over a period of 1 month. There you go: Um.

output impedance input level for the video and the audio Am noise and uh, all that sort of jazz linear Distortion uh For those really into their Uh video stuff, it's all exciting. Terribly exciting specs for this thing. Ah, group delay transmission. There we go.

nonlinear Distortion And as we'll see in the modulator unit, all this sort of stuff is a big deal. There's lots of tweaks, lots of circuitry in there to actually ensure that the video Uh signal. the video and audio signals are of the highest quality and they're all tweaked to absolute perfection before they transmitted out. output power variation within 2% the blanking level for the video.

Um, man, what else have we got? Modulation capability: FM Noise Am noise amplitude versus frequency response. It's you know, half a DB flat between that 30 HZ and 15 khz for example, harmonic Distortion .5% So if you complain, there's too much Distortion coming out of your video signal. hey um, your TV signal. Hey, somebody may have uh, you know, accidentally tweaked the Uh pot on the front panel here and they got with the various standards they try to uh meet.

Step respon resp here. Oh goodness. Power supply is Uh 240 volt or 38400 415 Vol Uh 3 Phase voltage fluctuations allow allows 2% Uh. frequency fluctuation allows 2% and power consumption.

Of course for the Uh model, we've got 5 KW Oh, go figure. and there you go. um ambient temperature range minus 10 to plus 45 operational power factor greater than 90% up to 95% relative humidity and they can operate these up to 2500 m above sea level. which could be important because hey, uh, you know you want to mount mount these things on the top of mountains.

pretty much that's where they go. So this is basic Uh block overview of what we're looking at: We got two of the items here today. As I said, we don't have the corrector here, but uh, basically we've got the Uh audio and video input over here which comes from the Uh Network you know, Channel 7 Network Headquarters or something they microwave in, uh, the audio or these days it used to be microwave, but um, noways it's sent via uh, you know, fiber optic or the internet or some other connection something like that. The raw you know what information they want to send on their TV channel comes from the network goes into the Uh modulator, which as I said, the modulator is the really interesting uh bit of kit here.

CU It has all the circuitry that allows you to tweak almost every aspect of the audio and video to get it just as you require it and then goes into the If corrector which um, uh, corrects for uh, phase and things like that based on the transmission output. because we have multiple transmitters in parallel, that's why that can be a big deal when you got a parallel system when you got a single Uh transmitter system I believe that one isn't all that hugely important and then we have our VHF mixer which as I said is just really a um, you know, a mixer, there's not much else uh to it and then uh, then we have our if Uh output, put our visual uh VHF signal and audio. You'll notice that audio and video is always kept separate right throughout this entire process. Here let's take a look at the If modulator, shall we? The video signal is First Fed to the differential amplifier and prevents uh hum from being superimposed on the video signal by the hum current flowing through the ground line.

Got to be careful. System grounding would be you know, super important in something in a complete system like this really would. So they're using uh, differential amps wherever they can. then after level adjusted the video signal which by the way there are various uh adjustments on the front panel here which we'll uh take a look at and even more adjustments on the top of the unit outside of the rack which you know, wouldn't you know you wouldn't sort of adjust those after the the things installed in the rack um is directed through the BNC U link on the front panel and is applied to the video corrector.

Here the video signal is subjected to various stuff pedestal clamping, synchronizing signal level control, and white clipping for all you uh um video afficionados who are familiar with video you know the Pal Uh video standard and it really gets meaty. Now the video corrector output is subjected to quadrature Distortion compensation at the quadrature detector which is an optional circuit and then directly when no quadrature corrector is used fed to the receiver equalizer. Now the video signal is subjected to precorrection of specified group delay for the receiver compensation. Huge amount of stuff going on here at the next transmitter.

Equalization The overall amplitude response to the transmitter and group delay are compensated again in case of the transmitter with a Sin diplex of the TX EQ is mainly for the compensation of group delay caused by the sin diplexer. So where this is all outside of the system now like the Sin diplexer as we saw before is a totally separate unit which gets Um fed. Uh, part of the signal gets fed back into here. After a level adjustment, the TX Equalization is subject to more pedestal clamping DC restoration is fed to the modulator.

Uh, then it goes through a bounc modulator and balance modulators are pretty simple. They just consist of four diodes. There's not much going on there at all as we'll see in the schematics. the if modulated signal is subjected to level amplification on the surface.

acoustic wave saw filter having the characteristics of a band pass filter, can currently forms a vestigal side band and low pass characteristic for limiting video bandwidth. The S filter output is ified and becomes the visual output of the modulator. The video corrector, quadr tool corrector, and clamping at the modulator may be disconnected by means of a available switches applicable switches. Oh goodness.

I You know the amount of effort that goes into ensuring that the video Uh signal is all good when it comes out of this thing is just absolutely phenomenal. And then we've got the audio Uh one as well, which is a separate audio path to the video. as I said all the way through this thing, completely separate audio and video. And there's the block diagram of the audio path of the system.

differential Amp of course it got some pre-emphasis on there. um, oh, looks like fat attenuation there. That's interesting. Um modulator, oscillator, Vco Uh, we got ourselves an output divider phase detector got some PLL stuff going on there.

and then there's our Crystal main Crystal oscillator input. There's a circuit diagram for our FM Modulator there. As you can see, there's not much in these things. I Mean you know, single transistor.

They do have some uh variable capacitance diodes. very caps in there, but you know there's not a huge amount. But of course you know the theory behind uh, this sort of stuff. uh, working.

Gez, you could do whole separate videos on that. Then we have a very nice internal wiring diagram of here. Like here's all the uh stuff on the front panel, all of the connectors, all of the indicators on the front panel here, and this is all the rear panel stuff. and this is really there you go.

So we got multiple plug-in Pcbs, so that's what we can, uh, expect inside this thing. Separate power supply circuitry generating + 12, + 15, 10, and minus 10 as well. modulation. Uh, so we got a video modulator board.

that's what VOD stands for. Uh, we've got a color Equalization board by the looks of it and we have our video corrector board. and we have our audio modulator board. so looks like we've got quite a few boards inside this thing.

When we crack it open, then we can flick through other stuff like the if corrector which I don't have, but there was actually some reasonably interesting uh stuff in the if corrector there. and if you want to take a look at that, of course I'll uh Endeavor to scan this stuff in. And uh, there's the internal uh, block wiring sort of block diagram for our mixer which we'll take a look at. and uh, then we've got our Uh Power amplifiers which are all Solid State uh Power amplifiers.

By the way, these weren't uh, valve based power amps. So it' be interesting. there's the tetrode power amplifier. Ah, so this is Now We're getting into the uh, other parts of the rack here and as you can see so all the different components which go into this, we've got filters and things.

a harmonic filter. There we go. We got a 3D coupler here. Each one of these has their own little, um, own little section.

You know we're talking about the blowers inside. So the main, uh, wire, emergency stop button, all that sort of. There's the tetrode power amplifier, the screen power amplifier, the uh, bias screen power supply sorry, the bias power supply uh TX control unit which we don't have and woo, oh, look at this. It looks like we've got uh, some sort of uh, control sequence Quence? yeah, control sequence of the transmitter.

There you go. How it all works. TX Control Off and on because this is Woo! No shortage of stuff in here. Let me tell you, Unbelievable! This is great.

You look at this sort of stuff all day and then protection. We got a whole separate section on all the mechanical and electrical interlocks inside this thing. Here we go: how to turn the plate and how it turns the plate off. Emergency Stop Screen G Grid Circuit Plate circuit all that sort of stuff.

Cylinder key how the keys go in sequence as we saw in the previous video and setting and adjustment of this thing. how are you adjust it? Let's take a look look at all the work that went into installation. Here we go. Oh yeah, look at the cabinet I got pull out.

uh, these are all A3 uh stuff here. So yeah, there we go. Look at this. All hand drawn, all hand done.

NEC Nipon Electric Co somebody signed it I Don't know. Engineering checked approved all that sort of jazz. Look at that. Beautiful.

and they had to go through and produce all this lovely documentation for. you know, a couple of thousand units. Uh, basically sort of tops. There's the uh rack that we we've taken off.

Nice threedimensional drawings there. Very nice. All the air filters. oh my goodness.

Assembly of the VHF transmitter. Look at that. That's the transmitter part of the rack. Oh all the different parts of the rack.

Fantastic. Fantastic. Fantastic. There's more than you can poke a stick at.

Unbelievable. So yeah. I W Bore you with the details. I've already bored you with enough details here.

The plate power supply for example: Power Supply Circuit Frequency Response adjustment How do Ah, Now we're getting into the video. The input signal level, waveform, modulation and voltages. Things like that: adjustment height of the tuning plate, length of the uh quarter resonance bar for the secondary tuning. Oh goodness.

Operation. Here we go: Emergency Control: Stop How it all works. Blah blah blah blah blah blah. Maintenance.

And here's what we'll take a look at first, which is the If Uh modulator and this will contain all of the circuit descriptions and the adjustments, how to adjust in detail, and the full circuit diagrams and the parts layouts. It's all here. Fantastic. Oh unbelievable.

Uh, it's roughly divided into a shazis and plugged in type printed circuit boards. There we go, so we know pretty much what we're going to get inside this thing thing. and uh, the audio frequencies. the uh yeah, they're the IFR frequencies of course that's a general uh block diagram operation of the board similar to what we saw before and video corrector.

Here we go. Here's how the video corrector Works look block diagram of the APC Loop all going on there. Fantastic. You got the feed, you got the divider, feedback, your phase detector PL voltage controlled oscillator so you got it all happening there.

It explains all how it works. This is interesting. Look at this examples of uh, is that on camera? Yeah. examples of pre-distortion curve for the TX Equalization predistortion curves for the RX Equalization the phase equalizer.

All this sort of stuff vital to getting the you know, the highest quality video signal you can. And somebody you know, some little old granny watches it on her old you know, crust y old 34 CM Analog TV filled with snow and yet you know here's all the gear. You know somebody's you know all fussed over all the details of the exact you know, getting the phase and the Distortion of the video signal and everything else right, the levels, and the oh man, and you know people just don't care. You know this sort of all this sort of stuff is all designed for.

Probably well over engineered in terms of what was required for like a regular, you know, analog. Uh TV signal cuz it's you know it's not that great. although I guess it's hard to say what happens if you tweaked one of those pots on the front panel what the user would actually, uh, see if this thing was out of, uh, out of, you know, out of adjustment, really. So check that out.

There's a block diagram of the generation and compensation of distortions in the transmitter and the receiver. Unbelievable. And there's the overview of how: the double balanced mixer Works Fantastic stuff. Not much going on here.

of course you just got two. Transformers You know, four diodes and it does all the magic. but the theory behind that. hey, that could take up a couple of fundamental Fridays And it talks about the Vssb filter, how it's double sideband modulated and all that sort of jazz, and oh, it's all.

H How the saw Filter Works There we go. Uh, so we'll probably be able to take a look at that when we open it up. Here's the alarm and metering circuitry, which is, uh, really, quite interesting because you know it basically gives you a visual indication on the front panel that there's a fault in an individual uh circuit. So they've got the signals coming over and there.

You know there's not much going on in here. they're just buffering those or actually, uh, you know, doing a bit of level detection there and a comparator. and just you know, switching. In this case, they're actually doing some relay switching I Guess that actually physically disables the Uh output? perhaps? I didn't know it actually did that.

I Thought it just indicated that something was wrong, but it looks like it may actually, uh, physically, uh, disable something I Don't know. That's very interesting. And here's all the adjustment pots available inside this thing. I mean just incredible.

Look, these are all that looks like the front. Yeah, they're the front. so that's the front panel. So there's all these little adjustment pots on the front panel as we'll see and that looks like it's a yeah top view.

So that's internal circuitry. They look aha different cards. so when we open it up, we're going to see different cards. Looks like we've got our audio modulation, our video corrector, our color equal Equalization, our video modulator, and our SPF there on the different and there's looks like a front panel board as well for adjusting stuff like that and our power supply over here.

So that's what we're going to see when we pop this stuff open and you probably getting quite sick of this by now adjusting the Am component stuff Dave Show us the hardware. Shut up and show us the hardware. Yeah, yeah, I'm getting there. Keep your pants on! Total characteristics of: The Equalizer Phase Equalizer just in the color phase Equalization Ah, adjusting the visual modulator.

A frequency response. Unbelievable. Woohoo! Here we go Have we got ourselves some schematics? Now it looks like we do now. These are really interesting.

It looks like we have one page per board basically, but it's a block diagram level, which could maybe follow the functional layout. They may have laid out the board to functionally match this block diagram. that will be interesting to see when we physically take these Boards out. So I may actually come back to these diagrams and then show you these and then the different parts of the circuitry.

Oh yeah, there's our fed attenuator that we were talking about Before there we go. Um yeah, Fet I don't know if it's actually Field Effect Transistor I Don't know. Um, maybe fet means something else I don't know in uh, this? Palance No idea. But yeah, we may actually come back to this cuz this is interesting stuff.

this that was our audio corrector audio modulator by the way. Then we got our video corrector and then looks like we got a color. Equalization So these are all of our different boards I Don't know if they'll actually have the block diagrams you know, uh, on the silk screen of these boards or not? Here we go. Here's all our internal uh drawings for the front panel and all the internal stuff.

but yeah, um, maybe they will actually have the all this sort of stuff. uh, silk screened on there. you know, like a the board? Oh no, Here we go. Here's all of our uh block.

Here's all of our component overlays. Not in sure of these boards or have silk screens. Actually, they may not. That's why they actually provide uh component overlays for each board.

but you can see we're all going to get all through hole. look at this. Transistors everywhere as far as the eye can see. little uh, trans little inductors everywhere.

Ah, it's all going Ic's look at this in the old uh, round metal can packages. Fantastic. That's what we're going to see inside. This thing.

looks like we' got some coax, uh, semi- rigid coax on the boards so that'll be interesting to uh, check out when we open them up. So there you go. I've wet your appetite for what we're going to see inside the Uh. and next then we've got the If corrector which we don't have and then we have the Uh mixer which we'll take a look at and so forth and so on.

Oh look hey look look at this. Somebody's photocopied this and this is interesting look. Got some notes. Here Here we go Jam No Sam is it Sam further through on Artan transmitter excited switcher VF mix the level maybe noise? uh, sufficient check must Tom There you go.

So they've got the original Uh notes in here of people who've actually worked on this gear and done stuff and maybe set it up cuz this is all the original documentation dating right back to 1981. Ooh oh look look at this. the temperature compensated crystal oscillators have which are done by a third party company I Believe they've They're marked on the front by a third party company. They've got their own documentation including all of the Uh, the specs and we got the schematic and everything else.

This is really, really juicy stuff. I Love it! Here's the Aging characteristics for our oscillator. Oh brilliant. We'll come back to that, but check it out.

There we go. There is our Temperature compensated Crystal Oscillator Circuits Parts list. These are for all the different typ because there's a couple Uh used in all the gear here. Here we go, they're actually bolted onto the Uh front panel.

There you go. They're a uh Kiniki Sisha lab. however you pronounce it so they're the main Um temperature compensated crystal oscillators in this thing. And lastly in the back here wanted to show you that TDA they got semiconductor section.

It's actually the data sheet section because hey, there was no internet back then right? You couldn't just access the data sheets. You had to have the data sheets photocopied and put in the back. So here's all the Silicon rectifiers. you know? Look at this 250 amp silicon rectifi in there in a in a tab uh pin package that mounts on the panel.

Man Unbelievable. Here we go transistors, 2sc 1889 transistors and then we'll get uh, there we go RF Power Transistor Brilliance 125 watt There we go. That would be one of the Um RF uh Power transist is used in the solid state uh Power Amplifier which will uh end up taking a look at positive rest 7912 voltage regulator and so on and so forth. All the motor roller stuff which you re recogize and there's probably some NEC chips.

Yep, NEC You know because NEC of course are a huge semiconductor manufacturer so they can certainly wideband general purpose amplifier. There we go in a package. They just rolled their own stuff right? NEC would you? Because this is uh, the whole rack and systems designed by it's solid state reays. Ah man.

NEC did tons of semiconductors so they could just roll their own chips whenever they wanted. There's is a juicy overall uh block diagram for the 35 Kow in parallel transmitters I Love it with the combiner that's the complete coaxial switching equipment outside all the SS that we had look at in the previous videos. So the whole system level uh block diagram Brilliant. So I know I waffled on there and uh, yet some people that may not have been interesting, but I find this sort of documentation fascinating and look at it.

That's just one of the manuals. I mean that's just crazy I mean this doesn't even include the power amplifier example that's in the second volume of this thing. It's just crazy. The amount of work, the amount of people that must have worked on this back in, you know, 1980 to produce all this for something that they're only going to sell as I said, you know a couple of thousand of these things was phenomenal.

So I don't know how many you know engineer years of work went into producing that, but that's just awesome. You don't get that these days. So let's take apart the HPA 3696 NEC if TV modulator. And as I said functionally I think this is the most interesting unit uh, out of the lot because you know it.

It does all of the video and audio correction and tweaking and modulation and clamping and generating the way for you know, doing everything like that, doing the whole business and generating the If frequencies which then go off onto the Um mixer and then out. Basically you know, pretty much uh, sent out to the transmitter. So this does all the real interesting stuff. and uh, as you can see really nice block diagrams on the front functional block diagrams along with uh, fault indicators which there, it's not got fault, it's just got off.

So I guess this section is Switched Off it's foldy. the Le it'll light up and as I said, you can adjust uh little uh, little adjustment pots I don't know if they're 10 turn or single turn. we'll take a look at those but uh, you can adjust the modulation level, the white clip level, the sink level, the modulation level uh. and then we've got a frequency uh check output for our audio Crystal oscillator frequency check output for our video oscillator here and then what have we got line? We' got input here uh, which comes from uh, the inputs actually come from the rear.

These are the two outputs here which then go up to the Uh if corrector and then go onto the Uh mixer and then we've got some. A nice little panel meter here which allows us to do some tests you know, allows the Um operator you know, the technician to come along and sort of you know measure things. make sure everything's working huny Dory the power switch for example. you can't accidentally, uh, do it, you know and can't accidentally flick it off and kill everyone's TV all over Sydney cuz that'll really ruin your day.

So it's one of those locking types. you have to pull it out and that's the same across all this gear. It's designed so that you can't do anything really stupid to it and then take a look at the top. I Mean these are obviously designed to be uh, you know, tweaked sort of at the Um installation setup level and not actually, uh, tweaked.

You know, not for the technician to just come along and and you know T I Don't think you know Channel 7's looking a bit shitty today I think I'll you know tweak the uh, you know, the white clip level or something like that. So anyway, you got clamp receiver Equalization uh. Video correction pre enthesis: You can actually turn these off or on whether or not you actually, uh, want them in your system. Do you want video correction? No I don't want it.

thank you very much. Just disable it I Guess you know it allows you better than just taking out the board. Maybe you can't. The board has to actually be fitted.

You can't just take out the video corrector board cuz it'll be part of all the signal path flowing through this whole thing. So APC off and on transmit Equalization All that sort of stuff, you know, setup stuff and adjustment pots as well. All through this top. more adjustments and you can poke a screwdriver at and on the back here.

we got a huge uh, heat sink for the power supply obviously anodized. We got some power transistors with covers on the back there. We'll be able to take those covers off and have a look and uh, we've got our 240 volt AC input over here I Have no idea what sort of connector that is. It's a, you know, weird ass looking uh, three pin connector audio control output.

you know your guess is as good as mine. what that connector is I Don't know. maybe it is an industry standard connector, but hey, you know I've never seen it before and then you know we've got uh, jumper links like this for example and these things would have had to have been, you know, produced and supplied. Can we? Oh, I got it.

It popped apart, the seal on that was absolutely incredible and uh, you know they would have had to have made these engineered these to the precise length to to go on these and these are all over this. NEC Year There you go. Manufactured April 1981 There you go. It's 3 almost 33 years old number 344 so they didn't make many of these things.

And there you go. That's our video. uh, Tcxo and that's 38.9 MHz which is the intermediate frequency that the video signal gets modulated up to and which then finally gets subtracted from the local oscillator uh, frequency in the mixer which we'll uh, see later. And here's the audio one that is 8.35 01 MHz These are manufactured both of them in December 1980.

So there you go. They're relatively, uh, small units, actually, unless they extend a long way. uh, back into the input there. they're relatively small for a temperature compensated Crystal oscillator.

and what do we have here? What looks like some sort of weird ass old style lamp is actually if we Ro rotate that, pull it out. Tada fuse holder complete with o-ring Look at that. Jeez, it. Gone to town and look at what we have here.

The top panel here looks like it's designed to be easily uh, or come off for real easy servicing. And the way they've engineered that is to have a larger cut out there so you don't have to take out the screw and then lose the screw. So that's bad designed for servicing, so don't want that. So we undo the screw like that and we undo them all.

And then we can just D slide our pedal off. Brilliant! Here we go. let's pop this sucker off and uh oh, look at that. We got ourselves some nice felt in there, hold the boards in place.

Look at that. First thing I am going to do of course is oh, give it a smell. Yeah, that 30-year-old electronic smell. Beautiful The other thing you have to remember is this has been operational in a rack for 30 years and you know it's not like it's been recently serviced and I don't see any dust at all in this none.

Zip Beautiful. Looks like it was the day it was built and this is lovely. Look at this multi card construction with sliders with a big motherboard at the bottom which I'll show you but let's can I Just yeah, these aren't These aren't screw knobs, these are just knobs to help you. Oh, pull out a board and T T There's one of our boards and we'll take a look at uh.

each board. oh there we go. shielded on the back. look at that.

Beautiful. all the transistors, heat sink there lots of heat sink compound A lots of glue under the bot, hot snot under the bottom of that. oh that looks beautiful. Tada There you have it inside our main rack here.

all of the uh, individual uh boards, they're all labeled. Check out all the uh, all the connectors. look at these huge big beefy card Edge connectors really love them I Don't know who the manufacturer of those is but a they're beautiful. So big baseboard looks like I don't know.

We might have some sort of Reay or something over there perhaps. but look at all the Uh wiring. all loomed, cable tied and stuff like that. Got a couple of Uh components on the back there.

um, some of that. but yeah, all that's all. coax wiring all down there. Power supply, light over here obviously.

Oh, there's so much to take a look at in here. but really? I mean all of the wiring looms down in there. Then the coaxes are terminated, down to the bottom boards, to the baseboard down there. Like that little uh standoffs there, all individually wired on.

Very nice. Got some rigid coax happening here too. Check it out There we go. Got some rigid coax just flowing from there to there.

so the you know there serious rigid coax flowing all the way around there, right down to the bottom which we can't see. but oh beautiful. The amount of engineering that goes into this is huge and this really. you know it's hard to know if there's a bodge or not.

really cuz it's all sort of. You know it's not designed for high volume production, high volume manufacturer. They really haven't taken that into account. They're not trying to shave cost off, they just getting this job done.

and Engineering it well, but not well for in terms of like high volume production and automated assembly and all that sort of cost saving. all that sort of stuff which you get in consumer year. you're not going to find that here so you know they don't care if somebody has to sit there all day. and you know, hand wire all these cable looms.

hey, doesn't matter. And there's the front board which is, uh, interesting in its own right. Ribbon cable didn't really, uh, expect to see that in there, but obviously that's you know, some logic, uh sort of stuff going over to the front panel indicator board. some Reay action happening up here once again.

I Don't know, that's you know, it's K112 MC 5107 Not actually sure what that is. No, it's an IC it's got IC on it. so yeah, not entirely sure there. but uh yeah, that dries all the indicators and has all the uh, other pots on the front panel.

but that's not all. uh oh, now there's some high frequency stuff there happening because we've got some rigid coax going across here and across the top there like that. So yeah, that's all happening cuz that's all the modulation stuff. So that's all that video.

or if uh, frequency and uh, then we've got some coax terminated going down to the baseboard down there. and there is the back of our um, uh, tcxo there. so they didn't extend very far into here at all. They weren't very deep I'm quite, uh, quite surprised like that.

I Expect them to be a fair bit bigger. All right, let's take a look at some individual boards. This is our Uh Audio Oh modulator board. There it is.

I'm quite uh, surprised to see some shielding cans on the audio modulator board here, which we don't see on some of the other some of the other boards. uh, for the video for example. uh, you know, higher frequency stuff don't have these shields on them so that's rather interesting. and we've got some rigid coax on here as well going there.

Now, my theory that the Uh board would have followed. maybe the layout of the board would have followed the block diagram up here. No, not really. Kind of the case.

I mean you know there's our CMR pot over there. there's our input level pot. so these you know adjustment pots are in the positions of the switches up here. Oops, sorry.

I don't think you can see the top of that. but sort of. you know. So they're in positions on the board.

but uh, whether or not the circuitry I mean your differential amplifier is probably going to be that Beast There, it's going to be around there you would expect. Um, then our what's what they call a fet attenuator there? that's probably around that section there. perhaps? Um, the pre-emphasis is Switched off and on here. Looks like we got some regulation.

perhaps? Um, but you know I mean look, here's our phase detector and our divider that's probably under here I'm guessing buffer amps I don't know. Yeah, it doesn't. doesn't hugely follow here. So eh, so much for that.

And for fans of rigid coax, there, it is metal outer. There you go. and uh, there's the Um. there's the dialectric on the inside, plus the inner conductor in there.

Off to these nice little PCB uh standoffs here. Really a piece of be like turrets. There's our goldplated Edge connector that would been top quality. uh, gold pla in of course not some skimped one hung low thing you get these days.

Now that's interesting. Take a look at this resistor here, which is mounted on some PCB pins there and there. Whether or not that's like a repair afterwards, or whether or not they sort of, you know, assembled those at the factory. You still still see some flux residue on that from the, uh, soldering of that thing.

Um, they haven't and you can see it on the pins there as as well. They haven't actually cleaned up. Uh, some of the flux on there. Eh, that's a bit ugly, but still.

Ultra Reliable. 30 years later, Not a problem. This stuff was still operational and notice the cleanliness of the board. As I said, there's no dust on this thing.

Not a speck anywhere. But anyway, that's interesting why they decide to put that on there whether or not that was selected after they the value was selected after they assembled the board. I Don't know exactly and we have a bodge. Look at this.

We have a bodge wire going over there. There's not many. from a cursory glance of all these boards. there's not too many bodgers on here, but that's certainly one.

Check out the standoff for this: IC here. What? I Originally thought at first glance might have been some oooing hot milk glue is actually a manufactured plastic standoff specifically for the pins to come out because the pin out of this thing is much larger. I'll show you a better one uh, later where you can actually see the pins in. In fact, this one's actually better.

There you go, you can actually see the individual pins coming out of the package. NEC branded. Of course all these Ic's uh, most of them are going to be NEC uh branded Parts All the analog stuff but mounted on those interesting standoff so they really didn't want to mount those things on the board. And the reason for that? Well, the Uh pins are probably too closely spaced on there, so if they had the pins coming straight down and they, uh mounted these, you know, directly onto the board in there, then the wave soldering, uh process of this thing going on the bottom probably would have, uh, shorted those pins out during manufacturer.

So that's probably one of the reasons there's you know, this is not a very dense board at all. The components are very well spaced out. Look how they've cut and inserted little insulating sleeves on the base of these capacitors. Oh, isn't that gorgeous? And check out the original axial Capacitors electrolytic capacitors on here.

once again NEC branded. They're such a huge corporation, they did everything and uh, you'll not like they're the original ones and they got plastic. uh SLE they you know, like heat shrink tubing over those. so these ones look suspiciously modern and the solder joints on there indicate that these suckers have been replaced at some point.

So this board has been repaired and there's another pretty modern uh 220 mik, uh 10v axial capacitor there. but by modern hey, this could have been repaired 10 15 years ago, but it's certainly not 1980s original. We got ourselves some slug tuned inductors there and they've been sealed. You'll notice the gunk on there to hold those in place to make sure they don't come loose.

Somebody's got their tongue at the right angle and tweak those. And the trim pots there are rather interesting. Haven't seen that exact Uh type before I'm not actually sure who manufactures those. Surprise surprise upon closer inspection NEC Manufactur the pots as well.

There we go. I Took those Uh cans off and obviously they decided, uh, these two separate bits of circuitry were so critical here that they needed to put those inside those shielder cans. This looks like it's possibly the Uh divider up here for the Uh PLL uh, perhaps I would, uh, be guessing at that? We'd have to have a look at the Uh circuit diagram and Uh block diagram and take a look at that. But and trust me, you're not missing anything under there.

There's nothing going on on the bottom of these boards, so it's really not worth taking the bottom Shield off these things. And well, here's the full schematic diagram for it, which I found in volume 2 and the overall block uh schematic diagram which I found in volume 1 So it is actually scattered around the place a bit and this is just the analog modulator board which we've got here. and H yes I did find the fet I was after so that Fet attenuator up there I did find it I found a Fet in there. There you go I thought it was all discret transistors.

there's a there's a Fet and we've got ourselves of Darlington there. and ah, all sorts of things happening. There's our divider. uh, circuitry.

They got some waveforms on here as well, which is really quite nice with signal levels. So great for trou shooting stuff like that. All sorts of stuff all over the shop. so they're our uh, see if I can V see divide by 16 / by 16 / by 8 so they're our PLL um yep, that's what was under that can that I showed you there so they there're those chips there.

so I was right. that was a good guess. the divider. you can tell because you know they're sort of.

You know, there's a bypass cap on each each one. It's sort of a digital type uh configuration. There's not much analog uh, circuitry surrounding that bit on the input here bit on the output. so that's all part of the phase lock loop.

Dead giveaway. Aha, silly me. That uh Fet we saw before was not our uh uh Fet attenuator. It's over here, which matches our block diagram.

Of course you remember that there's our differential amp in. there's our Fet attenuator there, and that's exactly what we've got up here. There's our differential amplifier there, discret transistor, differential amplifier of course, and there's our Fet attenuator over there. and that's just been uh, Amplified by an op on the output Bob's your uncle So all of this schematic does really match that overall block diagram very nicely.

So you can like put these one on top of the other and you can go right. Here's our phase detector right here. and bingo, there's your phase detector going to be in there and you know it, really. So there's your DC, and uh, your low pass filters happening in there.

All sorts of stuff. so it really is, uh, quite easy to follow when you have the schematic and the block diagram here. It's beautiful. Service in this thing must have been a dream.

We've got ourselves an audio transforma here. 600 ohm output impedance that's coming out of here and that's going out to our audio output. So all that work just for an audio modulator aboard. There's a lot that goes into that I Hope you appreciate the level of engineering which goes into transmitting your TV signal cuz it's incredible.

This is just the audio part. This is just one part where they just modulate it and well, I can't go through every board in minute detail. We just be here forever. We've already been here forever, but take for example, this uh, video corrector uh board up here and uh, you know we got similar stuff sort of.

you know, discreete amplifiers uh happening here all NEC branded and you know, pretty much um, traditional through hoold technology and it was right when I mentioned before that this, uh, sort of stuff. You may have noticed it before on the other diagrams, but there you go: 9th of October 78 even though this was manufactured in Uh 1980 I think um, yeah, 78. this was designed updated, rev in 79. so this is potentially an older design which they've reused in a more modern Uh system unit.

And there you go. If you're curious to know what was happening on that board that's got the pedestal, clamp, the sink level adjuster, the white Clipper once again, a differential amp there video amp, and a uh, then the final video amp output. oh terribly oh, mono stable multi vibrator. then you got really jam-packed analog goodness like on this color Equalization board.

Look at that. Lots of uh trimmers in here because hence, you know Equalization you have to get in there and you got to trim everything out. Imagine how horrible it would be to sit there and calibrate and adjust all these things. Once again, we got some rigid, uh, coax happening here to take it from one side to the other.

These boards are all just, you know, double-sided board. very uh, coarse uh through whole layout. but look I mean you know there's hardly any bodgers on these boards at all So really, they did well to put these things together and then uh, you know, architected into the whole system. designed with the bus and everything else.

And wow. Then we got our video modulator board. Um, you know, not a huge amount happening on that that we got some rigid coax. We got another look at that mysterious device there, but check out that we' got a themister right next to that so there's some thermal compensation happening there.

And check out those two transistors there. They've put a heat sink, um, over both of them, but it may not be a heat sink, it may just be for thermal Equalization uh to try and match those pairs thermally. Oh, and by the way, the reason this one had so much stuff on it? There you go. It's got a phase equalizer, uh, receiver and transmitter phase equalizer, and then uh, four stages of, uh, pre-emphasis there before it gets to the final amplifier output.

and look at all the lovely parts list inside this thing that was for that video corrector. There's like 10 page part list for that. Fantastic. So really curious to know what that beasty is this here looks like.

There we go. That could be our uh, balanced modulator. There's our four dodes and our Transformers in and out. Let's see if we can find those on the circuit.

Diag yeah, I found it. There's our double balance modulator with the four diodes and the two Transformers there that we actually saw and that's coupled into IC 57 there, which unfortunately, that's what that thing is I'm rather disappointed. that's just an IC ah, MC 517 and but why? it's in a package like that that stands off on the board. and no, I couldn't find the data sheet for that thing in the data sheet uh, pack in the back of the manual there.

so it's just some sort of uh, you know, some sort of buffer. some sort of You Know video Power buffer wide bandwidth buffer. And last, we have our video Side Band filter and this one might be rather interesting. Not much in the block diagram here, but look at this oven temperature controller and there's our saw filter up there inside the oven.

There you go, Beautiful. So they're pretty serious about that uh saw filter that's for sure, and not much else you know. frequency response compensator, another buffer probably using the same one we just uh saw. So there you go, That's interesting.

and yeah, 1978 good on good on your tea. otami and check it out. This is the most interesting thing we've seen so far. This they've got mounted on a physically separate board.

here. on standoffs is the oven controller of course, and this for all the world, looks like the power element to heat this thing up. and the Uh Saw filter. The surface acoustic wave filter is inside there, so inside this big aluminium block.

this is obviously the uh temperature, uh sensor the the Thera coming out so you know they can keep the temperature of that Loop um stable. But there you go. So that is rather interesting. And there you go.

There's the big uh Power resistor on top of this thing to actually keep this thing. uh, you know, to warm it up. That's rather interesting. It's sort of like a a ceramic.

um, you know, laser. uh, trimmed. uh, you know, power resistor? it's it's. really weird.

I Didn't sort of expect to see something like that in here, that's for sure. Now, unfortunately, to get a look at the Uh saw filter inside this thing, then, well, that might be, uh, might be destructive. It certainly has to be, uh, desoldered from the board, that's for sure. And it could be, you know, glued inside there.

or uh, or something like that embedded. you know, potted even inside the aluminium. I Don't like the look of it. but anyway, um, yeah, exactly.

I was right. They've got exactly the same, uh, little power buffers there. those motor those um M NEC manufactured but MC 5107? what? I've done is, uh, taken the screws off for the back panel. so let's pop a look under the hood here and see if we can actually, uh, get that, see if it is potted or something else.

hello hello. We got ourselves some uh oh oh shielding cans on the bottom I shouldn't just disturb that now. I Got to put it back in place. Um, but that's interesting.

But look here we go. Here's the back of the board. Aha, there's our saw filter. Look at that.

um, huge number of ground pins, but it's basically a huge dip package, but looks like there's some screws for the aluminium block there. so possibly we can get that off. Look at some of the solder joints there. Not terrific.

I Mean this sort of stuff is, uh, the finish on the solder in there, not that great. Obviously, anything that's uh, hand solded. Everything that's wave soldered is, of course, absolutely perfect. but uh, anything that's been repaired.

What is that? Maybe somebody's actually, uh, repaired these? NEC Although they they, they may have been hand soldered after the fact. um, after the wave soldering? uh, process. potentially? So yeah. Um, that's probably why they're bit dodgy.

Here we go. I've undone the screws and now let's see if we can pop that off. Ah. Tada look at that.

There we go. It's just A. it's just a brick. basically an NEC brick seral number 152.

Look at that. So there you go. It's a, uh yeah, it's a sealed, uh ceramic package there. So yeah, I would to get in there and show you the Um saw filter, the saw element on there, the surface, acoustic wave.

uh filter. Yeah, we'd have to destructively take that apart and then hey, it may not be all that interesting anyway. and I'm not going to do that cuz that would be an awful shame to actually ruin this thing. It's interesting.

you can see some like soot marks cuz that just rubs off coming up. We're following the airf flow of this thing. Check it out there. we go coming up from here.

so obviously air is Flowing up through there or something like that and capturing that. Su I don't know where it's getting it from, but yeah. interesting. That's possibly the most, uh, interesting of the boards because why they've gone to the effort to temperature regulate that uh saw field up.

What is so special about it? Nothing else in this thing is, uh, you know, temperature compensated apart from the crystal oscillator of course, which is pretty critical to have stability on the main frequency that you're using to transmitter TV frequency. uh, all over the city. but yeah, there something like that filter H and I Just look back through the Uh circuit description and it unfortunately it doesn't shed any light on why that is kept uh, temperature stable. Presumably they chose uh, a sore filter for its uh performance to remove.

In this case, it's a um it removes the lower sideband frequency of 1 25 MHz and the upper sideband uh frequency of 5.5 mahz. and maybe they uh, they chose a sore filter for its performance characteristics. but um, you know, the technology of the time maybe dictated that? Well, you got the performance. But to get that performance out of your saw filter, you had to keep it temperature stable.

Maybe there was too much drift in there with the transducer. with Uh temperature? That's the only thing I Can uh, uh, come up with cuz they've gone to quite a bit of effort there just for you know, a a basic Uh video filter, but it uses a Um Saw technology. Yeah, maybe they couldn't get the Uh rolloff response of the filter they wanted electrically, so they have to do it essentially mechanically cuz a a surface acoustic wave saw filter is ex, you know, is essentially a mechanical Uh filter. Basically, it's um, it's got a transducer on the input, a transducer on the output, and some coupling mechanism in between.

And it's the physical characteristics of how the Um, how the waves travel along the surface of of the Uh device that there, or the medium that they're actually using inside there that determines its filtering characteristics. But hey, so they chose it I Think that's the only logical explanation. Chose it for the performance and then had to deal with the consequence of that in this case, temperature compensated. Now it's time to have a peek inside this power supply.

And I think this cage. two screws here. pretty darn easy. Even got some finger holes here to uh, yep, lift that off and too easy, huh? Look at that.

Check out those Phillips electrolytic caps here. We got three of them. nice big screw terminals on them. Uh, 15,000 microfarads, 40 volts.

Um, and look, they've got I've never seen this sort of package before. They're not completely round. they're actually flattened. It looks like I Originally when I looked at I thought oh, somebody's crushed it.

They've actually got the sides flattened down like that, so it's like a a six sided capacitor. I Mean it's round at the top and then they've got a little Ridge in there. but then these sides are are flat. It's rather interesting and they're all like that.

and we' got some big ass through panel Dio there. Look at them. that's our diode. Bridge Brilliant.

No problem with heat sinking. So basically what we got here is a big ass linear Supply We've got a dual uh Bridge rectifier here with our four big uh dodes. We' got three big ass, uh, 15,000 mik, 40 volt filter caps. It looks like there's a little relay board over there, so I'm not sure what that's uh doing.

that may, uh, maybe switch on the power after a power up delay or something like that. I Don't know. Not going to look into the manuals. There's the back of the panel meter down in there.

nice big uh wafer switch down in there, that's that. uh front panel selection for the Um for the panel meter. where to? you know what function to switch through to the panel meter and I have to flip the shazzy around to get a look at the board on the back which is for our linear power supply here Tada 2 SD 357 manufactured by NEC who would have guessed? and there's not a huge amount interesting on that uh linear regulator board I mean you know, eh, whatever. couple of huge uh Power resistors in there.

Incidentally, there you go. Once again, they've got those um standing off, but no spacer. none of those fancy plastic spacers we saw on the other board. a no way.

don't want to go to that expense on the power supply boards. I Don't know why they did it on the others and not on this one. Uh, who knows. Anyway, ancient stuff going on here.

Then we got our big ass Transformer in there and well, that's about all she wrote. But the interesting thing to note about this is how everything is just spread out. I mean they don't try and you know, cram this stuff in. They got the regulator uh circuitry right on the back where it needs needs to be near the pass transistors down in there.

Transformer All the um you can see the Uh Grill at the bottom. There gets air flow through. No problems at all. The caps are probably massively, uh, overrated in terms of uh, capacitance and uh, working voltage.

Got nice big heat sinking on your Bridge rectifier here it seems. or your dual Bridge rectifier seems much bigger than what you need, but that's what you'd expect in a uh, you know, a high reliability instrument like this because the biggest thing which is always going to fail in these things is your power supply. So I'm not sure the exact uh, you know the full power consumption this thing but it's not. You know it's not going to be huge and this over engineered linear Supply in terms of physical size and probably current and power dissipation and uh, everything else then um, you know it's it's to be expected because to get a long life on these things, you really need to over engineer your power supply.

so no surprises for finding that they've done it. Remember, this thing also has to live in a rack with all that other gear too. So just testing this thing on the bench isn't good enough. It's you know it's got to work within a system where the heat is always Rising But hey, these racks do have a forced air.

um well actually no, the rack doesn't have I don't think the rack has forced air going through it. uh, the valve and everything else and part of the you know the real high power transmission stuff does. I'm not sure this side of the rack actually had any uh, blowers in it. it? maybe it does I don't know I'd have to check the documentation, but anyway, there is no dust inside this thing thing at all.

It is a ridiculously clean considering that it has been in use. um, you know, basically since 1981. It's just unbelievable. the condition this thing's in.

it's It's almost as if you know it just rolled off the production line and we got one more thing left to crack open the Tcxo. Let's take a look. But of course, as I showed before, we have the full schematics and everything for this thing so we know what's inside. By the way, that's a lovely little uh, custom module.

You know that would not be off the shelf. This would have been, uh, you know, custom designed for NEC for using these products, no doubt. And I was wondering how they would have fitted all that circuitry that we saw on the schematic in there before and look at that very crude sort of, you know, endon construction. Very nice though.

I mean they've individually heat shrunk all the leads. Look at that, even color code them blue and yellow? That's just beautiful. Um, but yeah, it's really incredibly old school. Um, and all we've got is this case here.

so that's going to have the uh crystal in it and presumably a heater. but you know it doesn't really look like you know, um, like there's a