Hi quite a while ago I did a tear down of this Lroy 93 84c 1 GHz Oscilloscope 4 gig sample per second and if you haven't seen it, I'll link it in down below. check it out first if you haven't done that and as you would have uh seen in that video, this thing had a few issues and it had a fault and I haven't really had time to look into this thing at all I just checked the power supply rails and they were all fine at the time and well, um, just the other day I decided to uh, crack it open again and have another look. So this is going to be an attempted repair video and I say attempted because I have no idea if I'm going to be able to fix this thing, find the problem or whatever. So if you get to the end of this video and I haven't fixed it, tough luck.

All right? So um, this is like a real time, uh, a real time repair cuz I just powered this thing up and once again I measured the voltage rails again had the same fold as before and the voltage rails were all uh, fine and let's have a look at it down here and it was all fine. So I cracked it open and then I started to run it again and I was about to uh turn on the uh camera and um, you know, start troubleshooting the thing and then I found it just uh, you know it just failed. it switched off I heard a bit of a bit of a sizzling sound or something like that. Maybe it was my imagine I don't imagination I don't know, it didn't sound that great anyway and let's have a look at what I found.

If we get our here we go get our multimeter here and look at this. Let's have a look and here's the Uh: Power Here's the power. Here's the power supply here. It normally like sits on top all this metal work as you saw in the tear down or normally sits over the top of this.

I got it off and uh, it's got multiple rails. It's got 3.3 vol. Vol there is the yellow one, the orange one down in there is 5. Vols there's four of those or three of those.

there's ground. There's plus - 15. Vols there's plus - 2 Vols and um, a couple of other uh voltages there as well. and I think there's some sort of sense line as well.

Coming back. but after I heard this um Sizzle and it stopped working. um I measured the rails again and the 3.3 volt rail is dead. So I've got it on.

Ohms. and and if we have a look here, let's probe our 3.3 Vol rail. look at that 0.17 Ohms. Let's zero out our test leads cuz this is a very low.

We're getting about 61 milliohms there so let's zero that out there. we go and that is repeatable. There we go. Nicely repeatable down to plusus 1 milliohm I Like it.

and let's probe that again. That's our 3.3 volt rail folks. Just over 0.1 Well, let's call it .11 Ohms. And obviously it shouldn't be that.

and let's swap the polarity around just in case it's some sort of semiconductor Junction or something like that. No, it is spot on. It's 011 Ohms. So something on this thing has shorted out and I didn't measure the resistance.

uh before this uh happened of course. but um, that is definitely not right. Something is completely shorted and we're getting nothing on that. 3 3 Vol rail now.

So the power supply is shutting down. so woohoo! Excellent! This is what you're hoping for with a repair. You're hoping that you know a power supply like this will fail. At least you got something to troubleshoot.

So um, well. we're going to have to try and find the short on this thing. Um, it. You know.

Uh, in theory it could be like a, you know, a power plane in the middle of the board or something. It's more likely to be a cap or a component. but I have no idea how many Caps or how many caps and how many chips are in parallel on that 3.3 volt rail on here I'm assuming like maybe all of the memory up here. and uh, you know, a lot of the um As6 and stuff like that and a whole bunch.

probably all the uh, processor board. So let's start. We've actually got some things which we can unplug. So let's we've got the processor board here.

so let's uh, whack this out and measure that again because you always start with the stuff that you can. no .11 Ohms. You always start with the stuff that you can physically remove and if you got a couple of modules like this, there's the memory module there I don't know. Um, can't see any signs of visual? you know? um, the first thing you look for is uh, is going to be uh, visual stuff.

but we're not into the visual inspection yet. we're just removing these modules see if we can localize that short. So I hope I've got time to fix this today. I've only got an hour or so before I've got a head back babysitting little SE again so it's not that one.

There's nothing nothing visual on that board that I can see at all. Let's measure it again and I don't like our chances. No bummer, it's somewhere on this main board. Murphy every time Murphy will get you.

So looks like we got to pop out this main go board which is a Mong got to undo all the screws on here, lift it all out so let's give that a go. You've seen the bottom if you've seen the tear down. I won't bother. uh taking off all this uh metal work yet? because um, yeah we can you know? start with the power connector up here and uh, work our way around the board now I have no idea if this fire um is Rel Rel ated to the original uh fault.

So this, um, your short on the 3.3 volt rail is in any way related to the problems I was getting with the scope, all those uh waveform Corruptions and all that sort of stuff. It certainly could be because um, if you saw the previous video, you notice that the uh way it was kind of sort of working. It was sampling a sine wave but the memory was being all corrupted and stuff like that or it appeared to be so that could certainly be something to do with the digital uh 3.3v uh rail. So I'm hoping that, uh, whatever was causing the uh problem on the 3.3 volt rail before it could have been excess.

Ripple or you know, some other issue like that. um was loading down the rail and it was still working. but then it eventually failed and went kaput and uh, the Magic Smoke escaped and uh, now it's completely failed. So I hope they're related.

but Murphy um might intervene again and uh, ensure that they're not related and this 3.3 volt is a new fault. So even if I find this 3.3 volt issue and I fix it, there's no guarantee that it's going to fix the original fault. But fingers crossed. Now, when you're tracking down this sort of uh short on a board, you want the greatest resolution possible on your multimeter.

Now, this is a case where accuracy does not matter. You just want resolution cuz we don't care if it's 5% accurate, 10% accurate, or 0.005% accurate. We don't give a toss. all we care about is the resolution.

So let's take the Uh Fluke 87 in regular 3 and 1/2 digigit mode. Okay, we put on OHS We short it out. We've only got a lousy 100 milliohms resolution there. It's absolutely hopeless, right? And you saw that our short on this board was 0.11 Ohm.

So how can we trace this fault down to a lower, lower, and lower resistance? With that, you can't? You at least need an order of magnitude better at the very least. So put it in 4 and a half digigit mode and we get an extra digit of resolution in there. So the Fluke 87 in 4 and A2 digit mode like this? Yeah, we're going to see that last digit, but ah, you know it's not as good as it could be. Ideally, you want a like a 5 and 1 half digit meter for example, or at something like this Agilant 1272a which has a 50 ohm mode instead of the usual 500 or 200 ohm mode.

So you short it out and Bingo! we got 1 mohm resolution. so that's brilliant. So that's what I'm going to do. and of course we can.

you saw before we've got 1 milliohm resolution. Fantastic! This is what you need for tracing down a uh short on a board like this. or you could use like a bench multimeter or something. You know, if you got like a 5 and half digit bench multimeter or something like that, that'll do the job as well.

So we know it's not either of our other boards, it must be on this main board. So here it is again and there are three pins. These top three pins here are all the 3.3 volt pins. So if I get in there and get the third third pin down there it is now roundabout is up11 ohms and then the next pin up also .11 ohms and the next one up is actually is open that that's my there my fingers on the probe doing that so that top one is open so it looks like that top pin.

which is very surprising because usually that they're they're all shorted together on the board there and they're just using the three pins to get extra current handling. uh, capability through that. I mean the 3.3 volt one isn't the highest current? um Supply on this board I think it's the 5vt cuz it's got four wires on it. so usually they short them all together to a an internal plane or a internal track.

But let's flip this thing over and uh, have a look down here at what we've got on these pins. Now it's uh, often handy to know how many layers this board is and uh, uh, often. Well, a a well-designed board will. A multi-layer board will have these layer designators here and they're actually physically uh, copper.

and they've placed them on the different layers like this and this one. Here you can see number one is placed on well. layer number one, the top layer and then layer number two is under that, and then three, four five. And there's actually six there if you flip the thing over because it's physically on the bottom layer there.

So there it is. It's upside down there, but you can see 1, 2, 3, 4, 5, six. So we've got six layer board here. And as I said, in theory, the short could be on the internal Uh layers on the planes, but usually that doesn't happen.

Um, as a post manufacturing fault, usually it happens at the PCB manufacturing stage. Now these are the three pins we're concerned about here. They're shorted to ground somehow and um, I can't see those Um pins coming out on this top layer anyway to any sort of big beefy uh Power track at all. So clearly, um, they're not connected on the top layer here.

So we need to flip this thing over and have a look at the bottom layer. And here's the bottom layer. And here are the three pins. again.

and once again. Bummer, they're not connected through to Uh This Plane down here at all. but um, this is. you know this is more of a manufacturing uh type inspection really because you wouldn't expect um, you know, a working unit to suddenly fail and then to find a short on your PCB it's got to be almost certainly with inside one of the components in parallel.

But in this case, um, you know it's going to be next to impossible to follow this rail because it like physically follow it two components because it just goes off to an internal Uh Power plane somewhere which probably snakes across the board. They might have a whole plane in there dedicated to the 3.3 volt Rail and another one dedicated to the 5vt rail for example and then the other power rails. or it could be a split internal power plane or something like that. So um, uh, you know that's why you need these multi-layer boards cuz this power has to go everywhere now.

I Don't really have the exact Uh schematic for this thing I've got a schematic for the M model uh unit which isn't exactly the same and it's very difficult to read. So um, really, you know I pretty much we. you know we're going to do this without the manual Biggers Um and finding the Uh designator components. Anyway, of all the components on the 3.3 vol rail, what we're just going to do now is just um probe around.

Well, first we'll do a visual inspection of course. First step to see if there's any obviously blowing components, but I don't I've had a quick glance over it I don't think there is Um. So next we're going to actually, uh, trace this thing down and try and hunt down that value as it gets lower and lower towards um the you know the point where it's ultimately shorted. So um, with a Mohm resolution meter, we should be able to do that fairly well because any sort of uh, short fault on a product or any sort of product like this uh 1 milliohm resolution is, you know, is uh generally going to be enough to find Um to narrow down that resistance reading and eventually track down the fault.

now. I've taken off the metal shield on the bottom here and I you know I'm looking around and I can't see any components that are visually uh Gone Of course the thing you're going to look for most often is the Uh is the cap. So you're going to look for these tanms here. Make sure they haven't blown I don't know if they're across the 3.3 Vol rail yet.

odds are at least one of them in each of those Uh channels is I would be guessing and well, I can't see anything obvious there and uh, likewise, on the top of the board, we really have to, um, scan this thing over and uh, see if we can find any shorts at all. There's a couple of tanms down there. we've got a couple of big electrolytics here and there's one over there. there a couple of electrolytics there, but there's a whole bunch of little tanms on top on the analog rails.

But and no. I had a good look over this board and I checked for both the um uh, tanms, the electrolytics and other caps and I can't see any that have visually uh, failed I.E melted have a big uh burn hole in them or anything like that. So the next thing you're going to look for is the Ic's themselves because Ic's do actually fail and go short internally. it's not that uncommon and uh, generally you would look for like a like a burn mark in the center of the chip or it's you know it's indented or warped or something like that because that that's what.

like if the D inside is heated up and it's you know you've got Scr latch up or something like that. I've done a video on Scr latchup which can uh, cause fires uh like this permanent fires within the uh chip, then um or some other fure mode of course then you'd expect to see a visual deformity in the chip if it got bad enough, but not always. um Murphy will ensure that the fail will be inside the chip with no visual uh, you know, no visual outside clue at all that anything's gone wrong. So you're looking for little ripples or cracks in the tops of the chips, or little indentations or bubbles or something like that.

Or a big gaping damn hole in the thing perhaps? Um, but had a good, fairly good look over this thing and I can't see anything. What a bummer. So we're going to have to start tracing this thing down with the multimeter. So let's start tackling this thing.

Here is our 3.3 volt Rail up here. You remember it was that second pin down there. By the way, the other thing you're going to need is very sharp probe tips. Very high quality sharp probe tips to pierce the oxidization, um, on the solder joints and get right into those solder joints.

So you get the lowest resistance reading possible because you don't want variation when you're chasing a Delta variation in a contact resistance like this. By Delta I mean a difference. We're starting out with 0.11 ohms here and we're going to measure the differential as we go across the board. So we're looking for the difference.

So repeat. Ility is a key thing. So if these, uh, contacts are all dodgy and all you're not putting enough force on there, you don't want to get dodgy readings. And we're talking very low resistance values.

But as you can see, this thing is quite repeatable as we saw like you shorted out like that and it's 06. So ultimately, when assuming that we find our short, it's going to be around 0.06 If we get down right to that, then we can. You know, zero out the probes maybe and even track it. do some fine tracking right at the final point, but you know it should get down.

So we should trace it from 0.11 down to 06 and we can at least localize the area where the fault is going to be. So contact resistance absolutely key. Nice firm pressure on there so let's take a look. We've got our not Point H sorry this is our 3.3 volt rail so let's uh, go between the ground pin again.

There it is. Hey, there we go .16 Oh look, it's it's going all over the pl. Look, look at that. Oh I hope it doesn't disappear on us.

I've had that happen once or twice where I've been tracing the thing down, then it suddenly vanishes and that's when you're really having a bad mythy day. Let me tell you so. a it's gone up to 0.7 now so you know maybe you'd give the this is where you'd probably give the board a little little bit of a flex to see if it's a see if it's some sort of flexion issue like a physical issue within the components on flexing the other side here. No, no it's not I don't see any drastic change there on the board.

so 157 Ohms. Okay, well let's just skip on over here to these. Perhaps I Reckon one of these has got to be the 3.3 volt rail. I'd be a bit surprised if it wasn't No, there we go.

136 Ohms and climbing, That's another rail. Can you know we're obviously charging up? uh, the rail capacitance there. And of course, if you swap your leads around like that, you'll no doubt get something different. There you go.

So yeah, don't follow that. That's a uh, that's a red hering. So let's have a look at this cap here. Bingo There you go1 162 So technically that's higher than what we had.

So there you go. another rail. So that cap there? um, we've at least got one of those those caps. as I said on that, uh, on that rail there.

So we'll find that one of these caps. it's slightly laid out different here, but like this one over here will be. possibly yeah .16 They're all slightly different layouts. these boards.

52 Ohms. Yeah. Um, so all right, let's probably start probing some caps on the top and see. I mean we're getting a reference point at uh, this connector down here.

So let's measure s sort of something right on the opposite side of the board, shall we and see if that makes a difference. So if our power connector is over here, let's try and get something like right over in this trigger section over here. perhaps? so maybe not. I mean it's it's not a definite, but I don't know.

You'd assume that they'd maybe not in the trigger section. Maybe that's not. No, it doesn't look like that might be the case. But what about these little puppies down here? Maybe? although these look like local Regulators So we might be uh, 2.7 Ohms now I've had a quick little probe around these As6, you can see these four large um AC ADC hybrid uh modules here in the circuitry on the back.

They've got no, uh, bulk, uh, decoupling on there, just lots of small uh caps and I've probed quite a few of those and I can't seem to find any 3.3 volt rail on there. so that hybrid um, doesn't seem to use any 3.3 volt, which is not terribly surprising. But these other As6 or whatever they are under the heat sinks I don't haven't got the heat sink off to look at the number on there um, they that we looked at before? We can actually certainly Trace those. So let's um, start doing that.

I mean once again, our reference point over here5 2 OHS 0.151 I'm giving the board a bit of a flex there with my arm at the same time, which you probably can't see, but 0.152 Let's go across to the Cap here .154: You see how it's higher I mean we're talking what you know, 2 milliohms higher there. But but that is enough to tell us that it's closer towards here than it is here. That extra resistance. Now if we go over to here, we should see slightly higher.

So I'm assuming. So if this one is 157, let's say and if we go, you know if we know this point over here is lower, this one's higher then something over here should be higher again or over here should be higher again. So let's find the cap in there. I've got this on manual ranging now, by the way.

Um, just so it doesn't have to Auto o Hang on24 probably not probing that thing right there we go. No look at that, it's lower again. that's quite interesting. Point: it's lower .48 Very, very interesting.

It's higher over here, so this is now our lowest point. This is interesting. Let's go over here .154 and I'd expect this one over here to be higher. Oh oh look, it's Ch.

it's it's lower again. Has it changed? Oh yeah. look I'm putting actually that could be the solder joint although the others I was putting a lot of pressure on that .16 but you saw it go down before just a second ago to like close to 0.1 again put a bit of flexion on the board with my arm. No, a man this is I Was hoping this would be a good demonstration of troubleshooting this thing, but it seems to be all over like a tracing down a classic short on a rail but seems to be all over the shop.

a this is annoying I Just did that again off camera and once again it went down to11 ohms I swear it did and now it's back up soon as I press record, it's the white Coat Syndrome As soon as the uh people in the white coats come around, the fault disappears. that's what that's a classic industry term. So I'm going to actually Mark these uh, these ones with uh red so I can come back to them. that's the only one in that channel.

so I don't get to don't have to dick around again. The Ceramics in there as well are also um, across the 3.3 volt rail. So there's a whole bunch of caps in there. but it's you know if one.

if if it is one of the Caps it is most likely to be one of the uh, tanms uh, you would think it doesn't necessarily have to be in this section I still haven't fanned out over the board or anything like that. I'm just trying to get a reference point at the moment I find it hard cuz this one here keeps jumping around around, but it could certainly be that could be a Telltale sign that it is actually that um cap and well, I don't want to be a bit premature and go sucking it off and um, doing that yet? or maybe that could be a smart a smart move I Mean you know it could certainly be one of these Um chips which has failed. who knows? Um, cuz we can't visually inspect that cuz these heat sinks are glued well and truly onto this thing. I Don't think the 3.3 Volt is going into one of these ADC hybrid.

So um, that doesn't look to be a problem, but there's no bypass caps on the top really. so it all seems to be all the action appears to be on the bottom. Um I You know there's no reason I Target this area first other than the fact that it had it's I know it's digital. Um, because here's all the analog.

uh, part of the board: analog analog. It gets a bit. You know it's still analog up to it, hits the ADC hybrids here and then goes digital. and of course, uh, 3.3 Volt rail is going to be used for digital.

It's not going to be used for your Adcs and uh, front end. uh, typically. So um, you know something around here and then you're going to get 3.3 volt uh, rails over on your uh memory modules over here as well. But as you can see, they got no bulk.

uh, capacitance. They've got no bulk capacitance down on there. CU All the bulk capacitance is localized on on the Uh on the memory expansion board down in there. so they've just got a couple of Ceramics and it could certainly be a ceramic uh, for example, failing.

um, wouldn't completely rule it out, but uh, you've got to go with the odds when you're troubleshooting stuff like this. and yeah, I don't know I'm going to play around with that and give it a few extra little uh Wiggles and pokes and see if I can get it to uh, uh, do something consistent now. I've probed a lot of the circuitry around here and and as you can see, there's uh, not much in the way of bulk capacitors on here. just a few little tanms around this uh Shield here and all of this seems to be running from the 5V rail because if we go down, you can actually um, you know, measure the 5vol rail on the pins of these chips, for example.

oh sorry, you can't see the multimeter there, but it's showing a short which indicates shorted to the 5vt. well, you know, as it should be, it's uh, it's connected to the 5V rail so all this sort of stuff seems to be 5V um operated with a 3.3v rail being used on um, possibly the uh memory modules here I would suspect and uh, at least one of the pins on these as6 under here. So I'm going to I can actually prove that the memory modules let's plug that in and I'm guessing this would be 3.3 Vol logic as well. and yep, it is.

There's our .17 ohm so you can see it's higher than what we've been getting because it has to go through the contact resistance of the connectors and stuff like that. And you can see why the 1 Milli Ohm is important here. If we were trying to do this with anything less. um, like a 10 milliohm resolution meter like the Fluke 87 would be really, uh, pushing the proverbial brown stuff up a hill with a pointy stick or a pointy probe.

So I'm having a bit of a hard time tracing this thing down. It seems a bit non-consistent so there seems to be some sort of, uh, possibly physical U manifestation of the short which is not uncommon. um, to um, you know, vary with time and pressure and uh, you know, flex and all sorts of uh, stuff like that on the board. So really, it, you know it.

It's almost gotten to the point where well, I know that there's four Tanum caps here and you know I would always start out suspecting uh caps and I can't find any electrolytics um on the board that are doing that. So I think probably. Um, even at this early stage in the Uh tracing process, I think I might just go bugger it I'll get the iron out and just suck off those four tanms and uh, well see if we get lucky. I I don't think we will, but it's worth a shot.

only takes a minute and of course I was a bit off there. There's actually uh, two uh caps on the 3.3 volt rail. um on each of those channels except this one over here. And of course, getting these caps off is pretty, uh, trivial.

You get your two irons of course I've shown this before with your uh, wedge tips on them and get in there and bang and it's straight out piece of cake. And of course, what are our odds of that being the issue? I reckon buley and Murphy's Buckley and Murphy's yep .15 Ohms bugger. But maybe there's one good part about uh, sucking out those caps let's put that back on our manual range is that we now have some really nice pads. we can get down there with a lot of force and look on.

Wiggling those probes and look 0.156 so you can tell 158. So 159's climbing. So by wiggling those probes around, you can tell that that contact resistance is pretty good. So we're getting 0158 on that channel .156 so it's gone lower.

Let's check the cap next to it. 0.151 Oo right next to it. Really? 0.152 Oh okay, they're actually connected via Vas. like on Long looks like on Long traces right down there.

They're not a particularly, uh, low impedance path down there. 0.152 So we're getting lower and all the way over here. Aha, .158 Look at that. So is that consistent with this one? Okay, you see how that's higher these two are higher than this one here, so that indicates like that It's this area in here, perhaps.

Or you know, equidistant. Um, the short is equidistant between those. So let's do that repeatably. 0.15 160 Jump up to Channel three.

We'll call it 15 2 sorry 154. That was wasn't it. And this one seems to be the lowest 048. So there you go.

That one is and this one should be slightly higher again. 0.1 Oh no. 52 Oh bloody hell, it's all over the shop. This is really embarrassing.

Let's go up to the main connector up here and oh jeez, there's not much in it, but that is sort of sticking out a little bit now. I Found and marked red here I Found seven other ceramic caps which are on the 3.3 volt. Rail and well, really, we could keep sucking these off until the cows come home. Or uh, we can go to plan B which is, actually um, some people's plan A for shorts like this is, uh, hook it up to a high current uh power supply and see if we can blow the ass out of it.

So what we're going to do here: I've got my big Uh 40 amp power supply set it to 3.3 volts showing 3.2 volts on there. It's a smidge under and uh, it's capable of very high current I got some um re very thick, um well, quite thick, uh uh leads on it and I'm just going to apply this over the 3.3 volt rail. Be sure if you're going to do this, make sure you get the right polarity of course. Otherwise, you're going to blow your board up.

So um, now the idea of this is that, um, a couple of things could happen. Um, one, you're going to, um, heat up and uh, blow that short out so that then you will get that, uh, visual. Hopefully you know it'll smoke. Or you, it'll warp, deform, catch on fire.

whatever. Um, you'll get that visual indication of the exact component that's actually uh, failed. Or you could actually blow it and then blow it open and your shorts gone. Well, that's not so bad.

Um, because you you may blow it without any visual indications and if you do that, then uh, well. your board. you get your board powered back up again. But that chip or that cap or that part of the circuit that, uh, was, um, failed has, you know, is not going to work.

So then you're you know, back to uh, square One? almost? Uh, troubleshooting. Except you're not tracing a short anymore. you're tracing a, um, you know, a failed component. Um, so you know, uh, one or nothing can happen of course.

Um, it's You know it could just, uh, uh, heat up and you may not be able to, uh, find it. You may have to go over with, uh, your uh finger, try to find stuff that's hot or maybe a thermal imaging camera if you're um, really fan fancy equipped. uh like that or an infrared thermometer or something. you might be able to find the hot spot.

but I'm just going to uh, touch these terminals down in there and um I'm yeah I can't I'll try and uh, do this and we'll see what uh, the current Peaks up to. So let's give it a go. So hopefully um, here we go I Don't uh, get this wrong. So I got my black.

Going to the negative. make sure you don't want to blow the board up 1, 2, 3, 4, 5, 6. So that's our ground point and then our second pin. Here we go: 11 amps.

Woohoo! Something is going to be smoking. That's a lot. That's a lot of amps. So I don't know.

can't smell anything yet. This is why you need a heavy duty, uh power supply. so no, it's it's 11 amps and well now I can just whip that off, turn it off, and uh, maybe no, nothing. Uh, that's a bit of a bummer.

Not entirely conclusive, except for the fact that it's a solid whatever it is, it's a very solid short now. I think the power supply in the in this uh scope is um I think rated for about 6 amps on the 3.3 volt rail. so it's rated for half that. So um, it's uh, certainly not just the circuitry powered up.

but anyway, Let's uh, see, let's measure our resistance again and see if we haven't blown that thing out. No, we're still 0.16 Ohms there you go. Bummer. So anyway, we do have a very solid short somewhere in this thing, so I may have to leave it powered up a bit longer and I don't know.

Maybe try and find a hot spot now. I've got some uh, physical connectors in there now so I can leave these uh, permanently hooked up and I can start there we go I can feel that warm? that chip down there is warming up. That one's warm. Yeah, they're all warming up.

so these chips are all powered up I don't know I guess I just leave it for a while and see which one. I mean you know that is chewing a lot of power there. So uh, you know it's chewing in the order of like, you know, 35 Watts or something so it's a fair amount. so I might leave this and uh, see if there's any visual indications? Well, I've checked the temperature on know all four of these heat sinks and uh, they're all identical so it's not like there's one chip different and you'd go aha, that one's getting twice as hot as the others, you know.

Um so I don't know if that's their normal operating uh temperature there in the order of uh, 65 to 70 or something like that I mean this thing, uh, takes a lot of uh Power Anyway, I'm not sure if that's normal I the other service manual I had said um as I said, the 3.3 volt rail was uh, six amps capable or something like that. So, but it seems to be drawing uh, you know, in the order of 11 amps, 35 odd watts, and of course, nothing else is getting uh, warm with all these main Um hybrid adcs here, which ordinarily get very hot as well aren't and none of the circuitry over here. So as I measured before and suspected that, uh, none of this is operating on the 3.3v rail. um, you know, none of the front end.

nothing like that. um seems to be operating so it's only uh, these four devices here Plus the expansion memory. Oh, and of course the um if I plug the CPU board in there as well. the CPU might be taking some 3.3 volt as well.

but I've had this thing going for about 5 odd minutes now and well, nothing's smoking yet. Bummer. And of course, if the power supply in the unit was only rated for 6 amps on the 3.3 volt rail, then that would explain why it's shutting down and this one is powering it. Uh, just fine cuz the 3.3 volt rail actually wasn't you know working it had actually shut down.

All the rails had, um, all the other rails had stayed up and they were spot on. But the 3.3 volt rail was uh uh, dead. So um yeah, maybe that power supply was going into uh uh, you know, some sort of current limit mode or something like that and uh, it. it just wasn't capable of supplying.

whereas this Beast will go up to 40 amps. No problems at all. So it'll you know power practically any load you give it, which is why it's still sitting on uh 3.3 3 Vols So given that all four of these chips here are getting to equal temperature, it shows that they're probably good and uh, you know there's nothing. um, you know, wrong or blowing inside those chips, uh, at all potential.

you know, not 100% sure, but it's you know, a reasonable guess um that that is the case. So I guess all that's left. Really? if I think that this is O the only um part of the 3 3vt circuit is to possibly find every darn cap on there and uh, rip the damn things out. What a pain in the ass Now I'd like to uh, load test the power supply just as a matter of uh, course I was was going to use my dummy low but then I looked at the Uh manual and the Uh power supply at least on the M model.

I assume it's the same for this uh C model as well. that uh, the 3.3 volt rail comes off the five, the 14 amp capable 5V rail there. so um, you know it's you really have to sort of load down uh, both of them to check that it's actually capable of doing that and I've plugged it back in here. and yes, the 3.3 volt rail is still dead.

So um, whereas all the other rails are just, uh, just fine. really. So we're only getting you know there's like .03 volts on the Uh 3.3 Volt Rail and the 5vt rail is just hanging in there just fine and dandy. Well, as a matter of course, I did suck off every bypass cap on all of these Uh channels on the 3.3 Volt.

Rail and no, didn't find it. Of course we're still getting 06 ohms or thereabouts. and really I mean I am I chasing the red hair in here I'm not 100% um, sure that I'm not, but you know it seems likely because that is in an incredibly low resistance for a power. Rail And of course, uh, you power it up and it's drawing.

uh, double what the manual um, says it. you know, should that the power supply is even capable of on that rail. So geez, what's left? I mean I may have missed the odd uh bypass cap on here, but I'm pretty sure that the 3.3 is only around. Um, these four chips here plus the memory interface.

um, expand iion connectors here and I've tried I've measured. uh, lots of places elsewhere on the board and I cannot find the 3.3v rail going anywhere else. So oh man, all that's left are these chips. I suspect unless there's something else going on.

Oh I don't know. Running out of time here? Well, unfortunately, that is it for the day. I Got a head off but uh I hope you enjoyed that little troubleshooting exercise Anyway, even though we didn't. uh, get the happy ending we wanted.

Sorry, not all these things, uh, work out So yeah, um, if you want to discuss it, jump on over to the EV blog Forum if you got any, uh, good ideas of course. um, please do let me know. and yeah, sorry, these things aren't always easy. They do actually take time.

What did I spend on this? Like an hour or something and uh, I've well, I have you know, eliminated quite a few things. but yeah, we're still stuck. Something is going on I don't know. Anyway, that's real life.

Catch you next time.