Hi welcome to tear down Tuesday bit of vintage test gear yet again and it's a fluke Beauty Uh, one of the original Fluke Scope meter portable Oscilloscopes H vintage because it's 1996 or thereabouts. but jeez, you know, seems just like yesterday 96. You got to be kidding me. but that was 17 OD years ago.

So this thing is pretty ancient. Um, you know, comparatively speak in. so this is the Series 2. Um, so there was a Series 1 before.

This is a 50 MHz Fluke 91 scope meter. Here it is, um, scor it on eBay for about 50 bucks? Bargain. Uh, wasn't It was advertised as not working, but unfortunately it does actually appear to work. So I was hoping to get a repair video for this thing.

Once again, been foiled. Unbelievable. But anyway, should be really interesting to crack this open. Have a look inside a 17-year-old portable scope meter.

Let's go. and here it is compared to a Fluke 875 which is not a small multimeter in its own right. So you can see how huge this Beast actually is. Absolutely enormous.

It's probably not as heavy as uh, you'd expect actually, but jeez it, it is absolutely enormous. I Got some Uh probes with it. these weren't uh, advertised. basically.

uh, multimeter probes and oscilloscope probes as well. This is only the one channel model which we'll take a look at. Um, unfortunately. look.

check out one of the leads it's been. Look at that chopped bummer and it is the Fluke 91 Scope meter Series 2 50 MHz analog bandwidth um sample rate H Well, I'm actually. uh, not sure. it doesn't tell you the sample rate in the manual.

This was uh, back in the day when? well they thought a people are a bit scared. they don't understand this sample rate stuff. They want these things to look and work exactly like a real scope so well, we won't bother telling you that. but um, so it doesn't actually list in the manual on the specs what the sample rate for this thing is.

But based on the uh glitch capture of 40 NS Um, you know it's I think it's presumably that's um, the sample rate. It's got to be at least 25 MHz or something like that. so it's not a real time uh scope as such in that, uh, the sample rate is not. um, you know, at least four or five times the input uh, bandwidth for example.

but uh, you know, menu based uh interface the screen. It looks huge, but it's only uh 240 by 240 monochrome. Now this color garbage and uh, of course it's got multimeter and scope functionality as well. And if you have a look at the Uh top here, oh, let's flip that around, you can see that this is only a single Channel model.

I Didn't actually know they came in a single Channel model, but apparently they do. There you go and it's got regular uh scope inputs as well and you can apparently and a generator output as well. It can generate signals as well, and it's actually Cat 3 rated, which isn't too bad at all. And apparently you can use the common terminal in combination.

If you've got the Uh dual inputs like this, you can actually use the common terminal in combination with the Dual channels if you want to, or something to that effect. So anyway, um, it should be interesting inside this thing to see what sort of Technology it'll be, um, mostly predominantly surface mount or mostly almost all surface mount of course, but probably, um, not integrated in one large chipset. so there's probably going to be quite a bit inside this thing. uh, or most likely separate multimeter and uh, oscilloscope boards as well.

Uh, that would be my guess, but yeah, let's crack it open. Comes with this rubber boot of course, and uh, on the back here. I've taken off the Uh battery cover on the back. Let's have a look in here.

There we go: UL Listed Fluke Scope Meter 9444 There you go. Is that the is that a date code? maybe? I Thought it was uh, 96 or thereabouts. but check it out, folks! Made in Holland to all my viewers from Holland Beautiful. Um, it.

There does seem to be some corrosion down on the contacts down here and that's why it was sold as uh, not working because the uh guy sold it apparently. um, you know, wax some C-size batteries in it and uh, it didn't work. So he just sold it as is. Now as you can see rather curiously, you can see that it's uh, got an extra tab down here.

This is for the rechargeable battery pack so you can put in four regular uh, non-rechargeable C cells. And of course, if it doesn't detect uh using that tab, then it won't um, attempt to charge those. So so you can use two different types of packs there and also a 12. You'll notice these two here Mark 12 vs and zero Here that's for another pack which goes in which isn't a battery pack, but that uh, connects to a 12vt uh power source like an automotive, uh, power source or something like that and um, on the side.

Here we've got a um, a really deep uh DC input jack and an opto isolated interface as well. just a infrared transmitter and receiver via serial I'm sure. So yes, although this is a 50 mahz analog bandwidth uh scope, it's single shot bandwidth is, uh, going to be pretty poor. Unfortunately, its response is probably going to update.

rate is going to be very poor as well I'm sure. And the uh sample memory who hold on to your hat folks? Uh, 512 bytes? yep bytes. And that's the optional highres mode 512 samples. Normally it's only 250 6 samples, but you can punch a turbo button and double that.

Woohoo! So let's crack this thing open and uh, we can actually get in here with a flathead. believe it or not and looks like this panel, this end piece is going to lift off and that, uh and then there's only two other screws by the looks of it, so that should. Oh yep, there we go. Bingo oh look, we got little rubber surrounds on there to keep the dust and moisture and crap out and uh yeah is definitely the other one is certainly not fitted under there.

So there we go. that's coming apart already so it looks like um, oh, by the way, it's only it's only got one screw. it only came with one screw down here so maybe somebody's had a had a hack at it or uh, something like that. but I have powered it up and it does actually work.

So there we go, it's apart. It looks like it's going to flop open with a ribbon cable. Here we go. t Hey, look at that.

Oh beautiful. all right. What we got here. Beautifully laid out in two hars as you can see all of the Uh processing and display stuff all on this side connected via you know a a 25 way ribbon cable or something like that over to the main power supply part.

As you can see with all the Uh caps and all the battery management stuff and uh, looks like under here we've got all the shielded scope and multimeter front ends so uh that it'll be interesting to see I'm assuming that, say, the maybe the analog to digital converter is under here and uh, then it. it's just getting the data back over to the Uh processor side cuz there's no other connections. there's no, you know, high frequency uh or coax connections from one side to the other. so I don't think they're actually um, you know, outputting analog uh, stuff on this this uh ribbon cable.

so I can only presume that uh, the Um ADC and capture side and the multimeter front end is all under there. so I'll crack that open. We expect to see more under there, but um, let's have a look at the processor side. One of the first things I noticed is that they, um, interestingly divided this you can see on the silk screen, divided it into uh, a grid based patent and you know I H G1 2, 3, 4 and that's for um, uh, servicing, cross reference and stuff like that you know the component is located in, you know, I4 or something like that so you know I don't think it's needed on a product of this size, but I guess that was uh, fluke.

You know, internal uh, policy and way of doing things so the designers just uh followed that I probably and I can uh see a bit of that on the other board as well which we'll take a look at but um I don't see I all I see is a couple of custom fluke chipset. We'll take a closer look in here. There's another Intel device over here which we'll look at, but um, it is nicely modular designed like the battery sense circuit is around here. there's a receiver SL battery sense uh circuit.

there's external RAM contrast circuit around here and uh, they have, uh, labeled them and grouped them quite nicely I like it and we have uh, six, uh Hitachi LCD uh do Mak driver chipsets there all surface mount. pretty basic stuff. They've decided to integrate this onto the main board instead of uh, having that, uh, separately. You know there's a bit more engineering working that you could have, uh, divided it up.

Really? you could have divided your workload up and said, right, we're going to put all the display stuff on one board or something like that, but uh, no, they decided I'll bugger it, we'll just integrate it on a single board. Go! For Broke Um and you know it's obviously going to be, uh, cheaper to assemble and test and stuff like that and when it's all on the one board. But um, yeah, they're the design tradeoffs. When you're starting a design like this, well, do we make it? You know, a modular board for the Uh LCD display and Associated circuitry and then have a ribbon going over and stuff like that, and then you can divy it up, test them all separately, qualify them all separately, and you know, stuff like that.

So uh, there's pros and cons both ways. I guess in the end, it really comes down to your company's uh, particular methods or an individual uh, design team's individ uh methods and things like that and what they're trying to achieve. And we found the date code folks. uh, 9423 on uh, most of these chips around 94.

So um, yeah, that serial number on the back of or that date code on the back of the unit uh was actually correct. almost uh, 20 years old this sucker. So the manual said um 1996. So I guess the manual was last updated in 1996, but actually manufactured in 94 sometime now.

Bingo We found the main processor here. It is an Intel S83 C 196 part of the MCS 96 family of processors. This one's got 8K Uh, ROM built in and Um goes back. Copyright 1986 Brilliant.

made in Japan back when they made the bloody things in Japan Now if we take a look at uh, the layout on this thing, here's this custom fluke chip over here. it's the fluke. Well, it's got fluke masic on it. um I have no idea what that Uh stands for at all.

But clearly if you look at the Um memory interface on this I mean this thing's are capable of. you know it has external memory interface but it seems and here are the three. and here's the um. all the uh flash over here the program ROM So really, um, that seems tied into the fluke Asic down here.

So and then that. so it looks like it's some sort of memory controller or something you know. um, some sort of Asic that does memory control or something like that and it's also connected to the keyboard as well. You'll find that goes over to the uh front panel.

uh, keyboard. So really, that's a like a keyboard and memory interface controller perhaps? um, something like that with um Intel processor running a maximum of 16 MHz By the way, this thing and uh, what we got is 74 hc32 There couple of other miscellaneous got a resistor Network going happening around here, but this this, uh, main LSI there it is. it's another fluke Asic It even says it's an Asic on there and uh, well, yeah. I don't know how you go about getting info on that.

you probably can't uh, fluke proprietary so that's running at 25 MHz so you know you got to wonder what that's doing. It's got, uh, some memory interface to it here. So we've got a Noan 16bit processor down here. Not a bad 16bit processor for its day.

really. Uh, kind of what you'd expect to find in a product of this this vintage. And then we got the two um, As6 custom fluke As6 around here and they're both interfaced to memory. this one's interface to external SRAM up here.

So um, and also down to this flash down here. So you you know it's almost as if um, based on its location to the display driver up here. kind of like that is probably some sort of display processor or uh, something like that. That would be my guess.

anyway. and then this one down here, um, is just an external uh, memory and keyboard controller for this processor. So it's like the processor is maybe you know when they're designing this thing H This is an oscilloscope. You know it's got to process a lot of information, do a lot of stuff, update the screen, and you know, as fast as it can, all that sort of thing.

Ah, we can't really do that in a processor of this day, really. So we're going to have to do a custom I know? let's roll our own custom ASC up here to do all the uh, heavyduty display processing and stuff like that, perhaps. and another one down here to offload. Um, you know, some other task or something like that? uh, keyboard and memory? uh controller? Maybe a uh, uh, direct? um ADC to memory? uh, control or something like that.

So maybe the data is coming directly in from the ADC side of things and this Asic not being processed by the not being handled by the processor, but maybe being dumped straight to sample memory or something like that. Yeah, definitely. uh. controlling the display CU You can see the tracers snaking their way around here like this, going over to the uh uh, the display driver chips around here and of course they're all um, interconnected so that is the best.

Guess that that handles all of the uh Graphics uh processing and maybe um, you know, taking the samples and directly displaying it so the processor is not responsible for the uh, update, uh, rate and stuff like that. it's all handled by the Asic oh how cute. We' got an Lm324 and an old 4093 quad uh Schmid Nangate classic and that's looks like it's somehow that's like the Ram Power that's what it's got there. So I don't know, maybe what's it doing? Is it? You know your guess is as good as mine I Don't know.

But and if we lift this board out of here, let's have a look on the bottom. Yeah. I Didn't expect to see anything on the bottom at all and sure enough we don't. We just get some uh test pads down there.

You can see the manufacturing test pads down in there. all those gold contacts so that contacts there little gold pads. uh so that would have gone down onto a bit of nails uh, production tester and possibly use to program all the uh, flash memories once they're in circuit and stuff like that and looks like just have a bit of a shielded grid down here pattern on the bottom of the membrane down there. and yep, there you go.

Nothing special, but yeah, they've uh, decided to do that as a um mesh base one instead of a solid ground and down here we've got our soft latch onoff power circuit which would be continuously monitoring the uh onoff membrane switch on the front panel. Now let's take a look at what's going on on the battery side of things here and we've got some serious capacitor happening around here. Looks like we might have a big inductor or common mode choke or something like that in there. Looks like there is a common mode choke there for our DC power in and underneath this little shielded can I See two inductors down in there.

They're actually identical looking inductors to these things here. They don't look like inductors, but uh, they've just got uh, tape on the outside of that. But there you can see the windings on the Ferite core there. So yeah, we've got a decent amount of uh switch mode uh stuff happening there.

These would be low ESR uh caps. presumably top quality. What are they? Let's have a look. Does it say What Is that? a sexy brand capacitor? Well, they are very sexy Sxe and it turns out that's not not actually the brand.

that's the uh type. And they're from Nipon Chimo. Absolute top quality as you'd expect. And of course I missed that.

That's the Nipon Chemo symbol down in there. and the Sxe is the Uh series model of the capacitor and these are high temperature low ESR caps as I suspected and we have ourselves a current sense resistor. Folks there, it is 0.1 ohms, uh, 5% that's in series with the battery pack down there and I can't quite see the Uh M part number down in there, but it's a M part and looks like we've got four uh, Ferite beads there with a filter cap. So if you look at the Dave CAD drawing here, it just looks like that in series with the DC input jack.

And if we get this Shield off and look under the skirt, there it is. Hey, nothing under there. Not much at all. But once again, we've got that um, silk screen component grid happening which tells you where the parts are.

There must be, uh, more stuff on the bottom down in there. We got a couple of reays up there we'll take a good close look at that, but uh, looks like that board's going to have to come out to see the goodness on the bottom. Now on these. uh, portable.

Scopes If you haven't seen them before, you might think this is just a fancy red painted uh BNC You know, just a regular B andc painted red and you might think, well, how can it make electrical contact when it's got that red paint on there? Well check this out, folks, it bends. Not sure if you can can see that I'll get in there with the screwdriver. There we go. It's flexible, it's not metal folks, it's plastic.

And if you have a look deep down inside, you can see the real metal is somewhat um, inset right back down in that connector. And that is is of course for safety because you don't want to be um, you know, having you don't want to be able to touch any of the grounder part of the circuitry because this the idea of these uh, handheld meters is that they can take floating measurements so you don't want the idiot user to be able to touch them. There you go. That's a better view of how, uh, deep inside the real Shield part of that BNC connector is.

So while that looks like a BNC connector smells like a BNC connector, it ain't one folks. So you can't just go and use a regular um scope Probe on that and think you're going to get it to work. And yeah, it's just got the regular outputs here. There's the semiconductor, there's the ground.

incidentally, the ground is wet and this, uh, capacitor wrapped tightly around that, uh, lovely, beautiful look at that. Someone's gone to a lot of trouble there beautiful, uh, work and has solded that onto the ground connector. And that's AC coupling the ground or the negative input on that BNC through to presumably signal common and the internal shielding. And let's see if that's circuit ground.

So we'll go between the shield over here and well, let's go between the common terminal, the Uh negative terminal up here with the multimeter and yep, it that's actually connected through to the negative terminal. Okay, so the ground circuit ground, and let's let's just take this choke here. we can no, doesn't like that other side. Yeah, there we go.

It's connected through to the negative uh of the DC input check and the negative of the rest of the circuit here. But of course, the negative on the Uh BNC over here is not. It's AC coupled through to there and doesn't directly connect. As you can see, it's only you know it's 515 Ohms and I believe.

Um, there's an option in the Uh software to either ground that input or not via one of the Uh relays there, so that's all you know that depends on the measurement configuration that you're actually trying to do. And on the Mm side, of course, there's not much happening there at all. There's a couple of reays in there that one I think might be the one I just mentioned switching the ground in, but we've got a Mo there, We've got a high voltage cap and a resistor througho resistor and well, that's about it. There's not much on the top of this thing at all.

Boring is the proverbial batet and here we go. I Took the two screws in here out and I do like the design of this very minimalist in terms of uh screws. so absolutely chock a block. look at.

Look at that and look at that. It's a thing of beauty. a real steel plate. Oh love it.

and we have uh got a fair amount going on on this board. Here's our analog front end up here, which we'll take a look at in a bit more detail. The unpopulated um, well, almost unpopulated. the chips are chips are certainly there to duplicate that second Channel but the Bnc's not there and the Uh reays and other stuff on the Uh top side of the board aren't c ated in there to uh do the second channel so it's partially there so I'm not sure what's going on there.

and uh got our ADC up here which I recognize. we'll get on to that. Got some power stuff happening over here and uh, some uh looks like we got some um quad analog switches happening uh, you know, 74 4000 series Seos uh type stuff and another mysterious chip in here. Let's take a look.

The largest device on here I don't quite know what that is I tried uh Googling that no, um you know, nothing turned up at first pass. so I'm going to have to have another crack at that one. It's a Phillips yeah like Oq3 08 T 344 me I don't know may if I find anything I'll annotate this later. Then we got some 74 HC stuff for the data and here's an old friend: the Philips TDA 873 and I instantly recognize this because I've used this chip before in my own digital storage oscilloscope design.

the Dsoa Mark II uh, way back, um, year or two after this I think I did that in about 95 or thereabouts What? I think it was published in 97 or something like that in electronics Australia Magazine Anyway, here the TDA 8703 It's a Uh flash 8bit analog to digital uh converter primarily designed for video uh type applications, but you could certainly, um, use it for an oscilloscope and I did and it looks like fluke have as well. but you'll notice that it's only got a single ADC There is no second one and it's a pretty, uh basic flash 8bit flash converter. Really, it needs like external voltage references and stuff, uh, external level shifters and all sorts of things you know to uh uh, make the thing work but you know it's not bad. It's uh, 40 Meg samples per second not maximum.

so that's the upper sample rate of uh, this thing. obviously I'm not sure if it does actually get to 40, but curiously, um, uh, I Believe the Uh minus 3db input frequency range of this thing only extends to just under 20 mahz. So it's puzzling how they getting 50 MHz bandwidth using this converter. So what's actually going on with this? ADC I'm not sure because it's minus 3db bandwidth there only 20 MHz yet this this is a 50 MHz analog bandwidth uh scope.

So you know somewhere there needs to be an ADC capable of handling that, so the I can only presume that the only way they're doing it is some sort of sample and hold circuitry around here. um, maybe you know based on this analog uh switch here that is um sampling and then which is obviously uh, sample and holding the value and then it's being uh converted at a slow rate by the ADC when it's not in real time mode. I.E when it's doing equivalent time uh sampling which is sampling at a slower uh sample rate than Uh Nyus. So really I think that's what must be happening there.

Um. otherwise I can't see how they getting uh that minus 3db 50 MHz bandwidth on this thing H Go figure. Anyway, there's definitely only the one ADC there. uh, being um used to sample both channels unless this particular device is another ADC which is uh, you know, sampling at which has a higher bandwidth or something like that I don't know, we need to find out what that sucker is.

If anyone's got the schematic for this thing or the Uh service manual uh, please let us know in the comments or on the Eev blog forum and we've got a 74 HC Uh, 4316 that's a quad analog switch, and there's quite a few of those Uh placed around the board in various locations. So lots of analog switching. and that's what's They're using the same one over on the analog front end over here as well. so looks like we've got our analog um, it looks like we've got our input uh, Amp there.

We'll take a look at that. plus all the analog switching for the range stuff I presume and our input amplifi and National Semiconductor LF 453 No surprises there whatsoever. That's a Um Bfet, uh input, uh, high-speed uh Precision Op designed. you know, almost ideally suited to an Um an application like a ADC or a scope front end in this sort of class, and you'll notice down in here that they've cut a couple of isolation slots there and there, and those components which are bridging them like that are actually ceramic caps down in there.

there. They are four of them there, Three of them there. So they're isolating the signals between the Uh input section over here and the rest of the part of the measurement circuitry. And here we have a 27 Uh Mcac.

It's actually a TLC A, Texas Instruments TLC 27 M2 AC And that's a Uh Precision amplifier. They've got one sort of there in the middle of the board. Then they've got another one. curiously I Thought this was a matching Uh LF 4553 to up here, but it's not on Channel 2 down here and they haven't got the matching device down there.

it's that TLC device. So I don't know what's going on. We certainly don't have a true um Channel One Channel 2 mirrored circuit configuration here. and incidentally, you'll notice the largest solder pads on these outer pins of all of these chips.

and they're are solder thieves. Uh, they go under various names, but this is designed to be wave soldered and you can tell this board has been uh, wave soldered instead of Reflow solded. You know, if you look over some of the uh Power stuff over here, it's clearly you know. had the molten wave just go right over this thing and the idea of these uh, so obviously all the components need to be glued uh down for that to take place and then these, uh, just ensure that you don't get uh solder dags happening between pads, you just get as the solder wave goes goes over this thing.

you actually get a larger pad on the end, allows you to capture any excess solder that's coming off like that. and there's a signetics. SG 3524 d uh pulse width modulation uh Power controller so that's just uh, you know, paing some DC to DC uh converter stuff around here and LM 285 1.2 Vol voltage reference. And of course, there's one thing you'll notice uh lacking around the multimeter uh inputs.

or anywhere on this board is your traditional uh fluke multimeter type uh functionality doesn't have that fluke uh, input, custom uh switching chip, and uh, all that sort of stuff. So they're just using the regular Um scope ADC here for the multimeter functionality, they're just switching it in on a different uh Channel and that's pretty much it and that, and you can see the result of that in the Uh specs. The specs for the multimeter on this are pretty darn ordinary, but that's pretty much uh All She Wrote for the analog and multimeter uh part of the circuit I Don't know I was expecting uh, something a bit. uh, better than that.

just a you know, a Um 8703 ADC You know, shared between the channels if it has the Dual channels and still don't know what that one is. But yeah, there's not much happening there. it's all just you know data, the 8bit data output, and the clocks and things just uh coming from the processor board through that ribbon and that's all she wrote. Few little uh trim, few little trim pots around here just to uh, uh, compensate the well.

They're not even near the input dividers, so they're not and not for compensating the input divider, but they looks like they're somewhere near like compensating this uh, high voltage. um Isolation part of this here. so they're doing a few tweaks there. There's some diode protection going on there for the multimeter stuff I'm presuming and there's a amplifier for the multimeter and you know, H Pretty ordinary and they really have minimized the number of screws on this thing.

Look, they've got their their attention to detail. They've put the little uh PCB catches um in like holder uh, spaces integrated on the battery compartment there so the board sits under there. so we've got uh, you know, spaces under there which hold it in place and you only need the two screws or the four here, but it keeps all this front panel stuff in place. Really is quite elegant, all right.

I'll probably get lynched if I don't power this beasty up. So I've got it hooked up to my uh bench Supply up there. So let's uh, let's switch this sucker on beat woohoo and we're straight on there we go. Now One of the real problems with this is that the screen is just totally washed out.

I'm not sure what uh, technology they were using back then. It may not even be uh, you know, Stn or something like that. I'm not sure, but it definitely um I'm pretty sure it's faded. um you know because if this was its original uh contrast then well you know it's not that great at all.

and we can change the contrast like that. It reminds me of like the old uh TDS 210 Scopes kind of thing that um, you know that really washed out very low contrast look on it. So I don't know if anyone remembers using these. um back in the day, but I'm sure that they do age.

It's pretty horrible. Anyway, there's our there's our waveform. We can actually move it around and uh, we can feed signals into it and uh, it does actually work. It's as slow as a wet week.

Absolutely terrible. The Uh menu system is absolutely atrocious. We've got the like. the scope meter.

We can actually change it to meter mode like this and it actually displays our waveform. plus our multimer up the top here. That's not too bad at all. Um, that works reasonably well.

And then we've got Ohms mode. There it is. Whoop-de-doo We got Diode mode and external M volts. Yeah, I think so.

You know it. It's not that great of a multimeter really. in terms of specs. they've just added it in as a bonus.

I mean the combined multimeter? Um, and the multimeter, by the way, has got a 5 MHz bandwidth. So um, it's pretty. It's pretty good actually in terms of uh, what a meter is capable of in terms of bandwidth. So that's one of the awesome aspects of using the 8bit.

ADC But then you know the multimeter well. it's only using a crappy 8bit. ADC It's not that good. actually.

come to think of it, that's probably what that other chip on the Uh board was that I couldn't quite get the number for. Maybe it's another higher resolution ADC just for the Uh DMM part of it. uh, not entirely sure so any. Anyway, what we have here folks is uh, let's say we're in scope mode.

then we can get into Submenus and then we've got to use the menu keys to hang on where how do we no more scope and then we can jump around in here and there's our our capture length. We can set that to 10 or 20 divisions glitch detect 40 nond glitch detect that's okay and um, whether what you want to averaging whether or not you want persistence and stuff like that. So you got to use that and then you got to go select item and then you got to scroll down again and you can get infinite and you can change the Uh width of the trace and you can do do all sorts of stuff. but yeah, really convoluted sort of operation.

Menu operation for this sort of thing, it's pretty I mean we do have dedicated Uh range Keys down here, so as you can see, it goes down to 20 10 molts uh per division with a a x 10 probe there, all the way up to oh 5 Vols per 10 Vols 20 Vols per division 50 Vols per 100 volts per Division 200 volts per division, 500 a kilovolt per division with a 10 To1 probe and the time base uh goes down to 10 nond per division in equivalent time sampling mode. Of course it's not a real time uh sampling scope below I think 100 nond per division. but of course, obviously you're only going to get that 1 kilovolt uh per third division with the optional high voltage probe for this thing. and I actually got three of these PM 8918 uh, 10 to1 scope probes with it.

Really quite neat. One of them, as you saw, had a big uh cut in it, but uh, let's see if we can feed in a signal here. See what we get? All right, I'm feeding in a 1 khz 5V peak-to Peak sine wave. So let's press the dreaded Auto set button, shall we? You can hear the reays going click click click click and yeah, there we go.

There's how can I move it I can move it up if I hold down the button. there's yeah, there's overshoot on the way, like it sort of. You have to be very delicate. You can't hold down the move button, but you can see that one volt uh per division there it is.

Bang on five divisions. Awesome. And then if we go down here to user options and go into meter mode, it should pop up with our waveform which is uh off the screen. There hasn't scaled that correctly and it can't measure it, presumably because it's off the screen and there we go I just uh, ranged it down a bit and we're getting 1.75 Vol RMS AC that's at 1 khz.

Let's up the frequency and see what we get there we go. There's the same wave form again at 4 MHz because as I said, in meter mode, it's only got a bandwidth of 5 MHz So let's put that up to five. see if we can measure that? Yeah, it can. Let's go up to six, see if we can still measure that.

No overload. There's our 6 MHz sine wave there. so let's bump that up to uh, say 25 MHz shall we and see what we get? And there's our 25 MHz Uh, sine wave at 10 NCS per Division And let's drop the time base right down and we'll probably see some alias in here as we drop down. Yeah, you can see it's going to start to do it here.

We go there, we go. drop the time base down. Yeah, there we go. It looks perfect, doesn't it? You would think.

Aha, look at that perfect S Wave at 50 micros seconds per division? What? Nope, that's aliasing and there's a 10 megaherz square wave. It's not handling that. too bad at all given the bandwidth. So yeah, this thing isn't uh, exactly a user friendly, uh, modern scope, that's for sure.

But it is. You know, a 19, uh, early '90s and 94 vintage almost 20y old uh oscilloscope technology here in a handheld form factor and Incredibly useful for its day, especially with the 50 MHz um bandwidth. And you know the basic multimeter functionality and uh, stuff like that? very popular little units these fluke scope meters were. so if you've got any, uh, further info on these um, service manuals stuff like that? I'm sure everyone would, uh, love to see them.

So please, uh, uh, post them in the ments or jump on over to the Eev blog. Forum when you can discuss this ancient stuff. I Love it! Vintage Tesy Vintage. Oh 1994 You kidding? Vintage? Unbelievable.

Anyway, if you like tar down Tuesday Please give it a big thumbs up. Catch you next time! Hi! welcome to Tear down Tuesday It's another bit of vintage test gear and it's a fluke. Woohoo! One of the first handheld multimeters multimeter. It's bloody oscilloscope.

.