VOGONS


First post, by Lostdotfish

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So I picked up this motherboard off eBay a few weeks ago. Sold as working but when tested, dead. No beep codes nothing. Dead dead. Well, if you listened very very hard to the connected speaker, you could hear a very very faint pulse...

Well the seller ignored my request to return it hoping I'd go away. And I did, long enough for eBay to step in and refund me. Which leaves me with 1 dead Super Socket 7 motherboard.

On closer inspection, I noticed it comes completed with Wendell Capacitors of Doom from the height of the last great Bad Cap pandemic. Of particular note are the nasty green cans of death all around the CPU socket.

Cue a Bill of Materials for the complete replacement of all caps on this board. I ordered Panasonic FR series caps for their low ESR rating.

CE1	1000uf		6.3v	8mm	12mm
CT30 1000uf 6.3v 8mm 12mm
CT31 1000uf 6.3v 8mm 12mm
CT6 1000uf 6.3v 8mm 12mm
CT5 1000uf 6.3v 8mm 12mm
CT7 1000uf 6.3v 8mm 12mm
CT8 1000uf 6.3v 8mm 12mm
CT9 1000uf 6.3v 8mm 12mm
CT10 1000uf 6.3v 8mm 12mm
CT32 100uf 16v 6mm 8mm
CT4 100uf 16v 6mm 8mm
CT16 10uf 25v 4mm 8mm
CT22 22uf 25v 5mm 8mm
CT29 22uf 25v 5mm 8mm
CT27 22uf 25v 5mm 8mm
CT26 22uf 25v 5mm 8mm
CT25 22uf 25v 5mm 8mm
C74 22uf 25v 5mm 8mm
CT28 22uf 25v 5mm 8mm
CT23 22uf 25v 5mm 8mm
CT24 22uf 25v 5mm 8mm
CT21 22uf 25v 5mm 8mm
CT20 22uf 25v 5mm 8mm
CT19 22uf 25v 5mm 8mm
CT17 22uf 25v 5mm 8mm
C34 22uf 25v 5mm 8mm
C46 22uf 25v 5mm 8mm
CT18 22uf 25v 5mm 8mm
C24 22uf 25v 5mm 8mm
CT15 22uf 25v 5mm 8mm
CT14 22uf 25v 5mm 8mm
CT3 22uf 25v 5mm 8mm
CT13 22uf 25v 5mm 8mm
CT1 22uf 25v 5mm 8mm
CT2 22uf 25v 5mm 8mm
CT11 22uf 25v 5mm 8mm
CT12 22uf 25v 5mm 8mm
C38 47uf 16v 5mm 8mm
C39 47uf 16v 5mm 8mm

Stay tuned for the next episode of "Is it dead... or only sleeping?"

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Reply 1 of 4, by ykot

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I have a very similar motherboard, just "PRO" version, that will not cold boot. It also came with these green caps, but recapping didn't help - I've used polymer caps as replacement.

However, in your motherboard I see burned flux at the mosfers near CPU socket, so likely those have been replaced. I would guess that these have been replaced because of incorrect CPU placement, which caused short circuit. Have you measured CPU voltages at the socket?

Reply 2 of 4, by Lostdotfish

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ykot wrote on 2020-08-03, 16:54:

I have a very similar motherboard, just "PRO" version, that will not cold boot. It also came with these green caps, but recapping didn't help - I've used polymer caps as replacement.

However, in your motherboard I see burned flux at the mosfers near CPU socket, so likely those have been replaced. I would guess that these have been replaced because of incorrect CPU placement, which caused short circuit. Have you measured CPU voltages at the socket?

I haven't tested much of anything yet to be honest. Swap tested a handful of known good CPUs, ram modules and graphics cards and that was all.

The mosfet pads look too clean (other than the flux) to have been reworked (other than at the factory). I wonder if it was a component that couldn't be wave soldered and was hand placed as part of the finishing process....

I'm going to pop out all the 1000uf caps 1st and then try it again. I'd doubt the other caps are causing a problem but if that gets it working, I'll recap the rest for good measure. If not, well, it will have been a fun hour or so of soldering...

Reply 4 of 4, by Lostdotfish

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Intel486dx33 wrote on 2020-08-03, 18:28:

I purchased a lot of 5 of these motherboards a few years back. The fat capacitors near the CPU socket are the ones that bulge.
I would start with those first.

Yup, there's one in particular that's got a rounded top. The faint pulsing sound on the speaker makes me think the main power supply to the CPU is wonky and since those caps all feed it, they we're my first suspects.