EEVblog Electronics Community Forum
EEVblog => EEVblog Specific => Topic started by: EEVblog on December 30, 2012, 07:52:44 am
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EEVblog #405 - Lecroy 9384C Oscilloscope Repair - Part 3 (https://www.youtube.com/watch?v=60X8f8IDwz4#ws)
Dave.
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Something being "worth" depends a lot on how much money one has. I for example repair broken ATX power supplies, because this lets me save a little bit of money (and since I replace the caps with good quality ones the repaired power supply will probably last longer than a new one).
Actually, I try to repair everything before giving up and buying a new device. If I can do it, I save some money (because the replacement parts do not cost as much as the new device).
That scope maybe has protection against bad power supply - without 4 rails the CPU might not have displayed anything at all. Or the power to the CRT may be provided by one of the dead rails.
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This video makes me sad, it's odd, I had a pet dog (it was in a state of ill health, 17 years old) put down earlier this week and it didn't make me feel this sad :S Dammit weird electronics people :(
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It's kindof a downer that it's dead, but if it's dead, what can you do? It's too bad pumping several amps into it doesn't set the thing on fire... ;D
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Ah well.. Sometimes it just happen. :-BROKE
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Just juice it up with 40 amps! ;D ;D ;D
Alexander.
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send it to photonic induction
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Even greatest people can't always succeed. Especially in electronics, where n+1 things can go wrong. Sad to see that scope is hopelessly dead, but there wasn't really high expectation after 1st or 2nd video. But hey, now Dave have time to something better, maybe it is just good that this thing is left rest in peace.
Btw, I would my self take that CRT display and it's circuitry and try to reverse-engineer it, I love those old amber/green mono displays, and actually I have one working unit under my nightstand xD
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Better to lift it with the Quadcopter and release it from a height, at least it will make for a nice bang...........
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Hi (My first post :D )
Would it be possible to get that little heatsink off to see what that ASIC-ish IC is?
//c
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@obsoletemac , Dave said that it would be very hard and you need chemicals that he doesn't have to remove the glue / thermal stuff..
Probably easier just to look it up in the schematics in the other thread :)
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Now it is off you just use a heat gun and cook till well done ( and a little smoky as well) then the chip will basically fall off the cooked epoxy.
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does anyone else think it might be the second asic? It did get 2 degrees hotter after all. :-+
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Probably all 4 are CBB inside from the power supply failing and dumping the 5V rail onto the 3V3 rail before the internal fuse popped. I have seen many ATX supplied die this way, though generally the 5V line protection operates and kills the supply.
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@obsoletemac
@SeanB
As RoelA said: much easier to check the manual. At least for the one who does the job. Why ask Dave to do something that you might as well do yourself?
It's an MDX622 demultiplexer + peak detect monolithic IC
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Excuse me for being rude but please RTM
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Auction it for charity.
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Yep, time to give up on this thing. It is now officially a boat anchor. If even one of the ASICs is bad, it is not economically worthwhile to repair. The process of troubleshooting was very interesting though.
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Something being "worth" depends a lot on how much money one has.
hmm, i think you wrong. It depends on how much money you could get in the same time if you would
simply work during this time instead of "wasting for repair".
Each every "free" hour we have can be calculated back to money, each time you don't go to work
(because you wish to have your free time just because you wasted it before by doing your hobby)
you can count that money.
Of course not every have a job, or not everybody really care about the free time (e.g. while writing this
i wasted time anyway, so it could be sometimes to "use it" more useful instead of typing ugly long text)
Actually, I try to repair everything before giving up and buying a new device.
yeah, i still remember my Yokogawa Signal Gen repair. Due the moisture (actually i think it was cup of coffe and an idiot)
one of the PCBs was complettly broken and another one partially. I had to restore many digital and analog traces - and
parts as well. I got the Gen dirt cheap, so i spend only "time" and parts. Finally, after i counted only the parts i was
already over the "used gear" price, not funny eh. And of course, i spend a week!, to restore the PCB.
So finally i spend, with work hours and parts, about 3k USD. For that money i could nearly buy a new one.
But yeah, i does not means that i gived up and not repairing things anymore, sure i do it still. However
for most thigns - unless it's just really unique or really cool thing - i'm calculating the time and money i wish
to invest, and if i'm over the limit then i'm simply stopping (and selling such things for few bucks to compensate a bit).
In Dave's case, in ym opinion, he reached the limit already.
Auction it for charity.
yeah, good idea
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Looks like the LeCroy is as dead as the Monty python parrot, time to take it out and give it a decent send off https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif (https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif)
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Looks like the LeCroy is as dead as the Monty python parrot, time to take it out and give it a decent send off https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif (https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif)
Absolutely!..................Would love to see Dave set fire to the LeCroy.......it's job is done.
Ian.
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Thanks for the excellent troubleshooting, and proper evaluation on when to say enough is enough.
While the scope is beyond hope, the amount of knowledge passed on in the process made this a massive success. Happy new year.
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+1 :-+
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I wish Dave would at least cut the 3 other chips off to show the short going away.
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While I am curious about the real cause of the short and failure I also think we've had enough of this scope already. There's just nothing interesting more to do with it. Time for a different video.
Wel, actually there is something that could be interesting, but it would have to include destruction of the board, preferably photonicinduction style.
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I would remove the other three ASIC-ish IC to see if the short was gone
the board would be nice and clean then in case somebody donated four new chips
you never know
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I wish Dave would at least cut the 3 other chips off to show the short going away.
and the short still exist and it was all along under the metal can :P
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Something being "worth" depends a lot on how much money one has.
...
Actually, I try to repair everything before giving up and buying a new device. If I can do it, I save some money (because the replacement parts do not cost as much as the new device).
I have a different opinion. If it takes you 2 hours to fix a product that you could purchase for less than your hourly wage, it doesn't make much sense to fix it. Just do some overtime or work a couple extra hours and buy a new one.
Edit: Looks like tinhead already said the same thing.
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"One sick puppy" now put to sleep...
Still it was interesting to watch Dave investigate the fault and I learned one or two tips for faultfinding electronic gear so it wasn't a complete waste of time - Thanks Dave. :-+
Some of the posts on this thread makes me regret the lack of a "Like This Post" button on this forum!
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Yes, every time I try to rate a thread I get an error that I am not allowed to do so..........
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Now, it's (definitely) will not work :)
But I laughed, with the drill - grinder
good job, Dave!
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To make sure that it's the ASIC's that are faulty, aren't there specific signal levels that you can measure on their pins to pinpoint the fault, rather than to make assumptions. I am only asking the question.
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Which IC (diode or capacitor?) Is broken? not verifiable ....
The damage can be any item, and this multi-layer PCB
I do not know how to run a (paths) supply
In practice, the service, to replace the entire motherboard goes.
Dave good try ... but unfortunately the damage probably somewhere in a hybrid system .... and they probably be GaAsFet technology ....
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Dave
Did you every try figuring out which are the 3.3V and GND pins on that ASIC, and probing the chip itself to see if you can measure the fault?
(How sickening would it be at this stage to measure the power pins and find evidence of a perfectly normal, working power supply structure in there?!)
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Considering that probably 40 or more pins are supply and ground around that package it will be hard to check, they often are not all connected internally, or have a high resistance between them. Often you find digital, analogue and io supply and ground rails, and application of voltage between them with others not connected can cause the chip to latch up.
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I am still curious to beat up against this snag, and hope to get a Part4
To certain sure the Asic are not involved scratch off the other two due the power pins story at the reply above here,
yeah we must have seen a temperature rise by scratching off the first one which was not
Therefore i think it is a "short" between the copper planes 3V3 and GND
the copper (power) planes are very large and therefore all contribute to dissipate this huge power loss therefore the board still looks cool 8) under heat detection camera
I think in one of the via(s) like mounting hole or other one(s) a tiny is short exist between the copper planes 3V3 and GND, Maybe it is possible to pick up the flow current by some probe at an scope to see where current is flowing,
other wise 3V3 trace can be cut to see if the short disapears and if there are none 3V3 traces only a 3V3 copper plane cut the pcb into half with a hack saw to catch and trace location of this snag
if the short has gone we know the short has to be at the piece of a half pcb :)
regards
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Just a thought, Dave probably created more media coverage on Youtube for LeCroy than all their other videos.
If I were somebody really smart in LeCroy, I sure would send him 4 new Asics and a new psu :D
Followed by the new HD scope of course...
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I doubt they even have parts for these models any more.
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I doubt they even have parts for these models any more.
They do, in fact, have some spares available (though I very much doubt that includes a motherboard or ASICs) - I enquired about buying a new front panel for a 9354 I acquired which had some broken encoders and they did still have them.
Admittedly the reason that the still have them is probably that they wanted more than twice what I paid for the 'scope so I declined. But if I'd had deep enough pockets I could have bought one.
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It's a bit of bodge but I have in the past successfully unsolderd chips like this by threading thin(ish) enamelled wire behind each row of pins in turn and pulling forwards as I reheat with a meaty soldering iron. As the wire slips out it lifts the pins.
You have a somewhat better chnace of having a chip you can reuse than if you use the Xacto Knife
Brendan
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[quote author=EEVBFan link=topic=13083.msg177673#msg177673
Therefore i think it is a "short" between the copper planes 3V3 and GND
the copper (power) planes are very large and therefore all contribute to dissipate this huge power loss therefore the board still looks cool 8) under heat detection camera
[/quote]
No way. You would easily see a plane-to-plane short under the thermal camera. Once Dave looked with the IR camera and the only major hotspots were the ASIC heatsinks it was game over. It was obvious that they were the culprit and all 4 were blown. Other components may be damaged as well, but those asics are dead dead dead.
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I know this is an old thread, but i cant stop thinking it is something under that metel can, surely it would have been worth desoldering it to be sure?