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Compaq Deskpro 386s/20n: Onboard VGA

This machine only has two ISA slots available, so options are immediately limited for anyone who wants sound, network and upgraded video! Currently the machine is running (what I believe) is a better spec VGA card and a Crystal sound card. I wanted to also try a network card, so I have endeavoured to get the onboard VGA working.

Rear plug - blocked pin?

The port is there, but back in the day they blocked pins so that you could only really plug in Compaq monitors. I don't know if this was to make sure that you gave money to Compaq, or if they were worried about monitor compatibility.

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Either way, I now had to either destroy a VGA cable or build an adapter... I chose the latter.

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The adapter was simple... just don't connect the blocked-out ground pin. It didn't work... well, it did, the adapter worked fine on the add-on VGA card. Once plugged in to the on-board VGA, with dipswitches set and the add-on removed the machine just didn't boot. No beeps, nothing.

Motherboard dipswitches

These are pretty simple. Smush in the top side to set them to 'ON', the bottom side for 'OFF'.

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As per the instructions.

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I love it that it says 286N. Silly Compaq... re-using old cases for new hardware.

No dice

Maybe that 'X' above the port was put there when the onboard video failed decades ago? I've no idea when, but it doesn't work. Hence why the owner bought an add-on video card? What are my options here?

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I straightened the pins that you see bent above, but that didn't work... I was a little sad... I wanted two ISA cards in there. This board could nearly be considered a total loss if it was partially-working. I have no real way of determining what else could be malfunctioning.

Maybe I should 'reflow' the board as described in the process here?

Reflowing, what could go wrong?

I killed it. I totally killed the motherboard. DO NOT REFLOW OLD ELECTRONICS. But this is what it looks like anyway... Bake away, pretty motherboard.

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The idea is that, by heating the board to 200 degrees celsius, you'll re-connect all the solder joints that have aged badly. I hardly put the thing in the oven for a few minutes (less than 5) but it stopped working afterwards. Turns out that the board uses tiny solder joints to connect the top layer to the bottom layer and most of these succumbed to gravity. None of my efforts to re-connect these solder connections worked.

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I managed to re-seat that PLCC socket and replaced all the electrolytic caps that were bulging... gah. I assume I've done massive internal damage to the ICs though. Meanwhile, the little motherboard top-layer to bottom-layer solder joints are all stuffed.

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Anything above or below that looks like a solder ball sitting on top of a hole in the board shouldn't be there. Above is the underside of the board and the solder has dropped out of the hole and is hanging in a nice sphere. If you look closely, and I apologise for the focus, you'll see 3 spheres, just below the right-hand-side of the edge connector. They shouldn't be there.

Below, if you see holes resembling black-heads then you'll realise that there should actually be a nice flush bit of solder there!

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I attempted to re-solder with my soldering iron... but a lot of the joints just wouldn't accept the solder... I'll store this board, I'm not accepting defeat just yet... but I'll need a solder-sucker and a higher quality iron to get it going again. If the ICs are dead. Meanwhile, another motherboard is on its way.

Maybe I should put it back in, upside down?

Defeated...

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About stevenh

Trains... trains... trains... + Electronics + Japan.
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