Hi. In our previous episode, our intrepid adventurer was repairing an Onkyo Tx Sr 607 surround sound thingamajig receiver and it had a non-working vacuum fluorescent display on the front Vfd although like the audio section worked and everything was fine and all the power supplies were fine except for one which was traced down to on a different board to the front panel vacuum fluorescent display board. This is why we left the previous video because the intrepid adventurer didn't have time to finish it off that day. But he's back today to determine to find this fault because it was traced down to this board here and the negative 35 volt supply voltage minus Vp here which was not being generated which is the negative voltage required for the vacuum fluorescent display and that was not on the vacuum fluorescent display board.

It had to go through yet another board over here on the side and then through a right angle board. uh, into this uh, Power Supply video mux. It's actually got a video mux on there, so it maxes all the videos and things like that so it was narrowed down to that. And when we left off, we had actually, uh tested this uh transistor here.

so we had that and put it on an external transistor tester. Measured fine, it detected it as a transistor. it had gain, but that doesn't mean it's necessarily good. There could be some we obscure high voltage breakdown in the part.

when you've got semiconductors like this, they can, actually, um, do you know weird and exotic things if Murphy's not on your side that day. but anyway, we're going to call that good. We could put in a replacement, but I think that's okay. So it's got to be some other part here, but unfortunately we can't power this all up and uh, then start probing voltages.

the uh, all the the transistor was on the top through hole, but the other parts are surface mount on the bottom here and you can't do that because the board has to plug into this right angle board over here which then has to go over to the display board in the front which then also goes down to this bottom main power amplifier motherboard which also eventually goes over to the mains power supply soft start switch. So in order to power the thing up, um, all these things have to be connected and it's otherwise it doesn't work. It doesn't power it up, so unfortunately, unless we hack it, it's not easy to do that. so we're not going to bother to do that.

but I'm 99 sure that the fault's going to be within here. We've tested this transistor. I think I tested that Zener. although this is a 36 volt zener.

so unless you take that out of circuit and hook it up to an external power supply, my 121 Gw multimeter here only tests up to 15 volts. so unfortunately yeah, we won't be able to test that unless we hook it up to a power supply. But anyway, I did actually measure that and it was a diode in one direction. so it's not like it's open or anything.

And these caps look okay, although I haven't taken them out. but really, a cap like that wouldn't cause a complete failure in this. So it's got to be one of the parts here. I think I might have measured that diet and was okay.

But anyway, I think what we've got left is we're going to go through and systematically test every single component in here until we find it. We'll desolder every component if we have to. so we'll bet we can measure the diodes. We can measure the resistors, although, uh, you know it's unlikely your resistors are gone open or something.

Although this one up here, this is curious. It's got list here. What this means is that it's a select on different model. So we've got the Sr607 up here, so it should be a 2.2 Ohm, But I don't know why it's so drastically different.

Look 2.2 ohms half watt or 82 ohms half watt. It just seems ridiculous. Um, that spread in values. But anyway, I don't know if anyone's got any info about that model and why it's 82.

It's got a radically different type of display or something. I I don't know. Anyway, Um, yeah, let's systematically test every part until we find the culprit thing. If we don't find anything, well, then go deeper down the rabbit hole.

but I hope it's in there. Okay, so let's just check that Zener again. We can, at least. uh, check one direction.

Yep, see. so it's You know, it's at least a diode. Um, so it's not obviously blown open or anything like that yet. The other diode is on top here.

So it's a through-hole jobby. That's good. Five Five. That's okay for a, uh, you know, like a, well, yeah, one in four, Double o' three.

That's hunky dory. Let's not look at the caps. Let's measure the easy stuff. We'll measure the resistors.

Let's see if one if one of these is open. That would, certainly, uh, explain it. Okay, we've got 220 ohms, one watt R901, One watt here. had to be on the front because the surface mount one water would be quite big.

215. Yeah, good enough for Australia and our 1910 and our 9010. We've got the Sr607, so we need 2.2 Ohms and it's that one there. Yeah, that looks like 2.2 It's pain in the ass to get vertical one here.

Not sure if you can see that. that should be 2.2 Hello, I'm making contact with that. Is that open there and there. There and there solder joints look good.

it's open. We shot the pros together. Wow. Winner winner chicken dinner.

That one is open there. It is 90 90 10. Uh, which is a 2.2 or what? Half a half watt? So you know it's a power joby. So this thing is going to heat up.

Um, and it it's gone open. That would explain why we're not getting out negative Vp here. Ah, okay, and now that's kind of embarrassing. That was just, uh.

two fixed exposure there because the white paper. If you don't know, you know you put the white paper in here. Then everything else is dark. So you've got a like fixed exposure and overexpose the damn thing anyway.

Don't count your chickens yet. Um, but we've found an open resistor, which should explain why we're not getting the voltage there. So that's all it was. All I had to do was not give up and just spend another five minutes on this.

But yeah, I had other stuff to do yesterday. So I released the video and uh, yep, that's a potentially all it is. That's the culprit that explains it. Now, I'm probably 90 percent confident if I replace that resistor, it's going to work again.

Um, so yeah, I don't think it's failed due to, uh, like you know, over current somewhere else, because our transistor measures fine. Our diode measures fine. This resistor here measures fine. So you know that is the main current path, so you know.

and it's not particularly high power, but there's nothing that sort of like shorted out and taking out that I think it's just you know it's just heated up and it's a poor quality resistor or whatever. Or it's just heated up for so long That it finally went, died in the ass and went open. Um, I've misplaced the transistor that I took out. It was in the socket here and I measured it and I've come back today and I can't find it.

So our transistor is missing. It's got to be within the 50 square meters of this lab. I found it. I found it there.

It is. sitting on the sponge doll. Yes, I know the sponge is dry. so there is the culprit.

It's a little, uh, carbon composition jobby and uh yeah. half a What? It looks more like a quarter watt resistor to me. It depends on the temperature. I have done a video on this.

A lot of people don't know that just because a resistor is rated at a quarter watt or a half watt or one watt or whatever. Yeah, it can survive at that wattage. But you don't realize that that wattage is actually rated at a ridiculously high temperature. So if you're dissipating, you know, half a watt in your half watt resistor, it's getting damn hot.

Yes, technically it can survive. it's rated for that. but generally you don't want your components to get that hot. So yeah.

Anyway, so I have to, uh, reassemble this. Unfortunately, to test this, I can't just power it up. I've got to like, physically, go to the effort to at least do a modicum of reassembly, to, uh, test our theory that that's a resistor And it should be. I'm 90 plus percent confident.

Unless Murphy is, uh, awake today, then, well, we could come in guts a bit. Confidence is hard. I repeat. confidence is high.

so it's not a lot of effort to put this back together. I get, or at least get it to a point where you can, actually, uh, power the thing up and uh, test your hypothesis. but uh, test your repair. So anyway, we'll just put a couple of screws back in there and just get the boards basically back and the soft start should power up again.

And yeah, just a few screws, just in case you don't want to come a gutsy and have to unscrew them all again. and we'll see if Murphy's sleeping today. All right, it's back together. Let's power it up.

I think I've got plugged in most stuff, or there's a few. Oh, hang on nice. And the receiver in the bottoms? Uh, flapping around in the breeze? Need to put a screw in that? Yeah, you can't see it there, but there is like a metal um, Rf, uh, tuner on the uh back and uh yeah, that's a metal can and you don't want that flapping around in there because it's just secured on the back by two screws and if you don't put the screws in, it, just flaps around in the breeze in the back and lays on the top of the power supply board down there. So yeah, it didn't want that so that could ruin your day.

Will it release the magic smoke? Will it work and not our standby leads on? Wha? Oh, flashing. Now it's flashing. Wasn't doing that before. Wow.

Just wondering if I forgot to plug something back in. But anyway. vacuum fluorescent display is not on. but that's that.

That's just like a logic function. It's detecting something it's not happy about. Um, ah, let me give it a once over again. I may have forgotten to plug something in, don't You wouldn't know what it was.

The back of the board here was touching that power supply which is grounded and um, yeah. I like. Well yep and it was. uh, it's let's not do.

let's not do it again. Oh no. hang on. Now it's flashing.

I swear the display was working a second ago. Oh god, what's going on? I swear I held it up like this and it was working. Okay, you can see the standby Led's on hit that it's not flashing. The display is working.

The display is working. I swear. Look game. It's very dim.

Fox? There you go. Tv tape. It's working. Winner.

Went well. See no, it just went and it flashed. Now there's there's some sort of intermittent connection thing. Something's happening because I physically just moved that then.

Okay, I'm going to put all these screws back in the back because they do hold all the boards in place. And of course, all the boards are right angle connected, so you could have a dodgy connection just uh, by leaving some of the boards flapping around in the breeze, right? So I screwed it all back together now. Um, you know the top's not on, but uh yeah, everything's back in place, so nothing should be flapping around in the breeze now. And that's a problem with these designs when all the boards are basically held together with, uh, certain, like physically with screws into the back, uh, panel, and stuff like that.

So anyway, let's power it up. There we go. We've got our standby, which should be the default mode, whereas before when we were actually, uh, playing around with this, it would actually power up by default on. So I don't believe that's the standard, but I think this is correct, so let's hit that volume.

It's very dim, but that's common for vacuum fluorescent displays, and I do remember it being very dim. That just happens with age, unfortunately. Yeah, but anyway, it's working again. Vcr, Dcr, game aux.

It's good enough to make it usable. Like you can actually tweak the voltage and stuff for the vacuum fluorescent display to make it brighter with age. but eventually you're going to come a gutser and they just fail. It's a thing with vacuum fluorescent displays like this, not my huge amount you can do about it.

We could modify it, but I'm happy that it's working. So that is a winner. Winner chicken dinner. Pretty sure it was dim like this.

originally. it is a relative's one. I do remember it. Uh yes.

slowly dying over the years. It's pretty old. It's like at least 15 plus years old I think. so.

Um, yeah. Anyway, there you go. Yep, winner winner chicken dinner. We fixed it.

It was in the end just a carbon film resistor that went open. But I hope you enjoyed that. Uh, you know, trip down the rabbit hole. The repair rabbit hole where, uh, due to the design and construction of this thing, we just had to like, you know, slowly eliminate things one by one check things.

It was the last power supply that we actually measured. Let that be a lesson to you. Thou shall measure voltages. And in terms of vacuum fluorescent displays, there are ones that specifically negative 35 volt rail that was dead.

That, uh, powered the vacuum fluorescent display. And that was it. It eventually went open. That happens with those carbon film resistors.

You know it is one of the failure modes. Um, and yeah, whether or not it's just poorly rated. I mean half a watt for that, Looks like a standard quarter. What Joby to me? So yeah, not terrific.

So whether or not it gets hot and everything, I don't know. But anyway, there you go. It could be poor design, could just be. I don't know.

Is this a standard fault in these sort of units? But of course if you were repairing these all the time, you'd you know, get a like a database of common faults and things like that. It's usually you know every product will have like a like a classic Louis Rossman repairing his Macbooks like there's you know, like half a dozen major things that fail. and that's and that's pretty much it That covers like 95 of his repairs or something like that. It's just like a handful of, uh, common fires and stuff like that.

So I don't know if you've got one of these and you've had a similar photo. Please let us know in the comments down below. But yep, that's an interesting exercise and certainly I don't think um, in the end, it was shorting against the chassis. Uh, there it was.

I think it was just the the connections are because all the boards in here are basically held in place by like rear panel screws and stuff like that. So we've got board to board interconnects and if there's any dicky contacts in there, um when they're all like flapping around in the breeze, you just move something it can you know move to other boards and it just yeah. And the ribbon cables and stuff like that, it's uh, it's all a bit how you're doing, but once it's all together, that's fine. that's rock.

Yep, still on rock solid. There you go. no wackers so that works. a treat.

So anyway, yeah, in the end, that was a real easy fix. but sometimes you've got to go down that rabbit hole to find it. So that being said, if you liked it, give it a big a thumbs up. As always, discuss down below: catch you next time you.