Hi, yes, it's the Lroy 9384 C Oscilloscope Repair again because people just could not let this one go. Um, if you haven't seen the previous videos, please do. Otherwise, this uh, won't make much sense to you. I'll link them in down below now people wanted me to Power this thing up even though it still has that short on the 3.3 volt.

Rail and see if it works well. Okay, fair enough. Here we go: I'm about to power the thing up I've got my um uh power supply around the back here for the 3.3 volt rail. My leads aren't long enough, so um, yeah, sorry about that.

You can't see it, but it's set to 3.3 Vols and it'll be drawing about 10 or 11 amps and there it is down in there. I've got that connected down into the 3.3 volt rail with the alligator clip there and I'm going to power the rest from the main power supply. so let's power this, suck her up and see what happens to it. Here we go.

I'm going to try and do it, try and power up the rails at the same time. let's give it a go. And there we go. And yes, it's drawing 12.6 amps.

Yes! I've got the memory um installed again I've got the Uh processor board installed again and I'm getting nothing zip I think it should have, uh, should have powered up by now. No no I think it's uh I think it's dead folks. There you go I might wind the wick up on the supply a little bit cuz I know there is a couple hundred molts dropping those leads. so um, there's it.

sorry, nothing zip NADA what? Thanks for playing! Well as it turns out, I just tried to measure the other rails and the 5vt rails up. The minus 5V rail up is up. but I don't see the Um-2 volt rail I don't see the plus minus um I I think uh, 15 volt rails. This is one sick puppy indeed.

So I it may become more of a a bloody power supply repair instead of and oscilloscope repair, but ah man, fail I'd expect it even if the plus - 12 volts didn't go. I'd expect to see at least the processor powered up now I've opened up this power supply. Don't get excited I'm not going to do a bloody repair on the power supply today I've got very limited uh time and um, it the plus. I've measured it again without any load and the plusus 15 volt rails have, uh, come back.

but there is still the Uh 2vt rail which is missing. So + 5- - 5 and plus - 15 are all working just fine. but that 2v rail has died now. I would have expected.

um, you know the thing to uh power up with that. but when I um at, you know at least the main processor and stuff like that to power up and at least give me something on the display. but those but that plusus 15 volt, those plus- 15 volt. rails die when I hook it un to the board under so maybe it's taking out something else as well and well, this is just one very sick puppy.

Now, as for the power supply itself, I Cannot see any that's obviously blowing at all. No blowing. Um, caps, no blowing. Uh Power resistors.

You know, no charred power resistors or anything like that. Um, you know you give it the smell test. Nothing really smells, um, out of place in the thing. um no, you know, big charred.

uh Power diodes or anything like that and it, you know it. Um, it looks just fine and dandy. So as far as the visuals go, it's uh, you know, no problem at all. So this thing would have to be, um, taken apart, dissected things, tested and measured and well, yeah.

I you know I don't know if I'm going to bother? Yeah, yeah, have a winge. um I just I don't think I want to spend any more time on this thing. Really? it's just, you know I I can't see it being a good investment. that's all.

So I I don't know I give me your thoughts, let me know. but gez yeah. I just don't think I want to spend the time troubleshooting this bloody power supply as an much as an interesting video it might make. Perhaps I don't know.

And anyway, it's not going to happen today. Sorry folks. and for those who ask, this busted Reay has absolutely nothing to do with the short at all. I believe this happened during the initial uh, tear down cuz it was a bastard.

Several screws, got um, threaded and caught and all sorts of things and I was Levering the board out. so I'm not sure if that uh happened, um during my tear down or not I don't actually remember it happening, but I can only presume that it did happen during that. It's got nothing to do with it, it's just a little break in the case of a relay. It's nothing and just to satisfy those who are harping on about removing this second Asic here.

Fine. I'll remove the second ASC and see if the short goes away. it's not. but I'll do it anyway.

Now this is a pain in the ass. This is stuck on to this chip good and proper with uh, thermal adhesive and you're not going to get that off in a hurry. um, short of some nasty chemicals or something like that which I don't um, have and really, um, the proper way to get rid of uh to suck off one of these uh chips is to use a hot air gun and a proper Qfp attachment to your hot air gun after you've got the heat sink off because this is a massive thermal mess here. So I you know you could probably heat it up.

um, with like, a you know, something horrible and nasty like a blowtorch and lift it off with pliers. Maybe. but H it's going to be really, really horrible. So unless you absolutely absolutely desperately needed this chip to be intact when you took it off, um, which we don't, we just want to get the thing off and see if it makes a difference.

Well, the easiest way to do it is to just cut all the pins around there and uh, there's several ways to do it. You could try and get in there with the scalpel, but the leverage. um, you know the the angles in there aren't very good with the other heat sinks in the way and stuff like that. So um I think I will just uh Dremel the pins off and see if that works.

Let's give it a go. Well, I was going to try the Dremel but the Um sanding discs I've got are unfortunately, um, just slightly too big to get in there. What a absolute bummer really. Um, that's not very nice at all.

So I think we're going to have to end. Really, the heat sink is too high. so even if I had a smaller disc to get in there, um, really, the uh spindle is going to end up uh, you know I'm I'm not going to I don't think I'm going to be able to get the angle in there. So what? I I am going to get in there with the scalpel blade and push it across like that and maybe that's not bad.

The problem with this is that you're putting a bit of sheer force on those pin so you could actually damage a pad which isn't that great so, but we don't necessarily care a huge amount about that. We just really want to get the get the sucker off. There we go. I think I managed to get all the way along one side.

I should be able to do the other side and the other three sides and pop this sucker off and look at that. We've got it levered up like that. No problems at all. and here she comes.

Taada There we go. Go! And there are those pins left over on there. You can see it looks like we didn't do any damage to any of the pads. I was, uh, relatively careful I was using the correct uh, tongue angle there, but there are a hell of a lot of leftover pins on there which we need to go over with the uh, soldering iron and just uh, wipe those pins off the pads and we'll be left with the pads cuz obviously you know they could be, uh, shorting out, uh, all sorts of things.

so we want to get rid of those and check this out. There's a fiducial mark on the board there you can see it and usually these are outside the Uh chip as a reference, but they've put this one under the chip like that. So the Um Vision system on the pick and place machine comes and finds the center of that chip. It looks like it's directly in the center of like that I'm assuming that it is, um, exactly the center and they've put it under the chip instead of the more familiar place.

sort of. You know, two marks outside the chip like that. Unusual. And here we go.

We're going to wipe off our pins now. You have to be really careful here. You got to set your Um Iron to a very low uh temperature like under 300 so that you don't, uh, apply excessive heat to the pad. Just enough temperature so that you can wipe these pins off.

And the other thing is, you don't want to wipe in this direction like that because then that puts Um increas pressure on the Uh pads and you can lift the pads so you want to swipe it long ways on the pad like that. So let's give it a go. Here we go there we go. If we just swipe across, we can remove those pins fairly easily.

Might have to do the odd second pass here and there. You can clean it up with solder Wick later If you wanted to solder in a new chip, but we don't want to do that, we just want to, uh, ensure that all the pins are gone and we can then measure the rail again. And there you go. Should be left with a whole row of, uh, very nicely tinned pads.

Now, if you wanted to, uh, if you're soldering a new chip on those, you might of course go and sold a wick, uh, some of the rest of it off. but uh, that is a very nice result. and that was a pretty horrible way to rip a chip off like that. But H really? I think that's probably the best available option.

I Um, had to hand. Really, considering that we didn't have to reuse the Uh chip at all. So yeah, well. only one thing left to do.

Let's measure that power rail. I Bet you it's exactly the same. All right, Here we go. Let's short our probes again.

compensate for that. What will we getting before? .11 Ohms On our 3.3 volt rail. There we go. It's pretty.

It's going to be pretty repeatable as we saw last time. I Don't mind these probes, they're pretty good. and uh. 1, 2, 3, 4, 5, six.

And here is our 3.3 volt rail. Let's see what we get, folks. Ha. .14 There you go.

So it, um, that makes sense. It has, um, yes, it has gone up from 0.11 to 0.14 but that's what you'd expect. We got one4 of the chips. Um, actually.

um, you know if if the theory is correct, then all you know something happened to the 3.3 volt Rail and it took out all for A6 on that particular um, uh, 3.3 Vol rail. So there you go. You would expect it to go up a little bit like that because we've now taken out 1/4 of the shorted chips. but I reckon that all of them are shorted.

That sort of confirms the original theory that well, the heat had nothing that tiny little what three or 4 deg seed difference between this chip and the others. As I said it, it didn't add up at all because just the extra power dissipation in there. It didn't uh, you know it, It just didn't make sense for it only to rise for a couple of deg. C All right, so let's see what that translates to into with the current.

We expect it, um, to be slightly less than what we're getting before, which was around 10 amps or something without power in the other rails. so the other rails aren't powered at all. and um, of course it's a non we already detered. It's a nonlinear uh thing.

so um, you know we expect it maybe to drop to I don't know, 8 amps or something like that, maybe nine or something like that cuz it is going to be shared across the Um Asex here. of course. And if we're and if our theory is right about the four 4 As6 all being equally blown or reasonably equally blown, we should see a percentage decrease. So let's have a look.

Tada There we go. 8.8 amps. It has actually dropped by. you know, uh, 1.2 amps or thereabouts.

I'm not exactly sure, uh, exactly what the value was last time it was around about 10 amps or so. So there you go. it's dropped in proportion. and I'm sure if we desoldered the other chips one by one and measured the current, it would drop in proportion as well.

So there you have it. I Don't think there's um much option left but to just simply give up on this thing. As I said last time, looks like all four of these chips are short Ed out on that rail. So something happened to the power supply.

We got a spike on there, something, it took out the rail. Um, no, we're not going to be able to get these uh chips anywhere. No, I'm not going to sold them back in I don't care. it's not.

even if I could get the chips. Ah man, it's not worth the effort and fixing that power supply and getting it all going again. For an ancient scope like this, no, there's no point. Um, sorry folks.

So there you go. eh complain all your but I think this one is dead and I hope I cleared up a few things that people wanted me to do on this thing. It definitely is a short inside the chips. on the 3.3 volt rail.

Something happened to that rail. the spike or whatever and it took out all four As6 on there. And I think if we suck off those As6 and yeah, we'd eventually, uh, get rid of the short. Whoop-de-doo What do we do then? makes for a great you know, paper weight I don't know.

Catch you next time time.