VOGONS


First post, by Steapa

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Hi! I'm new here.

So I found a place in my town where I can find lots of untested 486/386 parts dirty cheap. But many of the parts are broken and I need a way to avoid choosing them.

I'm want to build a 486 PC so I'll look for a socket 2/3 motherboard, 486sx CPU, 30-72 pin SIMM RAM, VLB video/sound card, controller card... Basically everything.

I heard that's easy to see when a motherboard battery leaked and to avoid them. There are more tips like this for other parts?
I guess this is a stupid question because must be hard to check if the hardware is broken only by looking at it, but I don't have another choice...

Thanks.

Reply 1 of 7, by chinny22

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Old hardware, new hardware it's all the same.
check for bulging capacitors, damaged/missing components against pictures on the internet but that's about and like you said only improves your chances of a working part by a fraction.

Oh and check that the ram slots still have the little clips to hold them into place as they often break. This wont stop the motherboard from working but annoying to figure out a way to keep the ram in place

Reply 2 of 7, by waterbeesje

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What chinny said exactly. Especially take a close look at smd components, check for broken legs or indication they may be pushed down (which can indicate internal damage to the chip)

Tantalum capacitors should be standing right up, or all bent the same direction. If they are bent unevenly or not all of them, it can be an indication of abuse. May still work though...

And ofc bent boards should sound the alarm.

And then still you can't be sure. If they are sold for dirt cheap I'd take a little risk once and a while.

Stuck at 10MHz...

Reply 3 of 7, by MaTi

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Can't you just reach out to employees in the shop, explaining what you are trying to do and see if you could buy a bunch of hardware, test it at home, and return whatever was unusable?

Still relatively new, but spending too much time on retro already.. 😀

Reply 4 of 7, by dionb

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Also, factor in what you know you can repair.

It's generally a safe bet that if a component has one issue not obviously caused by careless storage/transport, that is the reason it was thrown out. If you can fix that issue, you've got a good chance of getting a working part. Back when I was a cash-strapped student I trawled reject piles at computer fairs for boards with bad caps or mis-flashed BIOS. I managed to get between 33% and 50% working again. In the day, that let me keep my main PC upgraded for essentially nothing, as I sold the working boards I didn't need, which covered the cost of buying the piles of boards. These days the economical maths are different (for me at least), but the principle still stands: a board with a visible issue you can fix is at least as good as one where you can't see any problems.

Reply 5 of 7, by Steapa

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chinny22 wrote on 2020-08-03, 08:49:

Old hardware, new hardware it's all the same.
check for bulging capacitors, damaged/missing components against pictures on the internet but that's about and like you said only improves your chances of a working part by a fraction.

Oh and check that the ram slots still have the little clips to hold them into place as they often break. This wont stop the motherboard from working but annoying to figure out a way to keep the ram in place

waterbeesje wrote on 2020-08-03, 09:53:
What chinny said exactly. Especially take a close look at smd components, check for broken legs or indication they may be pushed […]
Show full quote

What chinny said exactly. Especially take a close look at smd components, check for broken legs or indication they may be pushed down (which can indicate internal damage to the chip)

Tantalum capacitors should be standing right up, or all bent the same direction. If they are bent unevenly or not all of them, it can be an indication of abuse. May still work though...

And ofc bent boards should sound the alarm.

And then still you can't be sure. If they are sold for dirt cheap I'd take a little risk once and a while.

Thanks for the tips. I will try to look for that.
I'll try to buy multiple parts too, like several motherboards and CPUs, to increase my chances of having working parts.

MaTi wrote on 2020-08-03, 10:06:

Can't you just reach out to employees in the shop, explaining what you are trying to do and see if you could buy a bunch of hardware, test it at home, and return whatever was unusable?

I don't know if they will refund me. Also, I need someone to drop me there and he's not always available.

--
Thanks for the help everyone.

Reply 6 of 7, by MaTi

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😀 Try calling them?
Especially if it is a smaller store, you might have the luck that the owner likes your story and is willing to help.
Also, he probably sees it as old junk anyway, happy to sell anything of it in the first place in that case 😀

Still relatively new, but spending too much time on retro already.. 😀

Reply 7 of 7, by Unknown_K

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There are not that many capacitors on 386/486 boards and not the kind that leak anyway.

I would look for:
Leaking CMOS batteries and corrosion.
Is anything missing (keyboard controller, cache, jumpers) that would mean the board was broken and somebody stripped it for parts before recycling.
Has somebody been tossing the board around with other boards, look for scratches that might sever traces or break parts.
Are the clips that hold the CPU heatsink or the RAM broken? Even if the board works that will cause problems.
Does it use a coin, barrel, or soldering on Dallas chip? A dead soldered on Dallas RTC can be a pain to fix.
Boards with cache are better then ones without (even on a 386).
Is the AT keyboard connector broken. The metal shield in front is soldered to the board and acts like a ground so if it is broken the keyboard will not function.
Look at the silk screen on the board for indication of processors and voltages supported. If you want to run a 486/133 and the board does not support x3 or x4 settings keep looking.

Collector of old computers, hardware, and software