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GA-468VM / RP2 resistor /motherboard repair

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First post, by Fairy_Dust

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Hello everybody 😀

I am new here to learn more about retro PCs. I've inherited some good old Computers from my dad and want to bring themback to life, because I think it would be a shame if they would sit in the corner , unused, or even would be thrown away. I've grown up with the good old Nintendo consoles, but recently I've also been interested in old PC game classics by Lucas Arts, etc. In order to be able to enjoy them and experience them firsthand , I need to fix an good old Colani Highscreen
with a GA-486VM Motherboard which is partially broken, to be more precise it ist part RP2 (a resistor-array ) but since it is broken and I couldn´t check the value , I have trouble to find the repacement.

Does somebody has experience with this board or can help me find the needed part , I would be really happy if someone has the same board 😀

Best gegards
Samy

Reply 4 of 9, by Fairy_Dust

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Thank you very much , I will purchace the part and let you know if it is working. But there is a lot of other tings to do, like fixing broken connections .
I will post my progress here soon .

Thanks again for your help 😀

Best regards

Reply 5 of 9, by Fairy_Dust

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Hey SSTV2,

I just got the 4.7K resistor pack and I was able to solder it in its place. While waiting for the part to arrive, I startet to repair the broken lines on the board. Since the damage looked quite severe and I had little hope for a successful repair, I was quite amazed that it actually booted up. So thanks a lot so far.
The only thing left to do , is to exchange the bios battery. I would like to use a Coincell but in order to do that, you have to disable the charging circuit.
Any advice to this kind of mainboard ???

best regards
Samy

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Reply 6 of 9, by PCBONEZ

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Congrats!

You can get rechargeable coin cells LIR2032 instead of regular 2032.
LIR2032 is available with solder tabs to solder to board and as a regular coin that will fit in a battery mount.
They don't cost much.
.

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Reply 7 of 9, by gdjacobs

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A 3.6V NiMH pack from a cordless phone can be used as a direct substitute for the barrel battery. It's also relocatable, so you can place it away from everything sensitive if it ever fails.

I'm not averse to lithium cells, but the behavior of lithium batteries under charge is quite different from NiCd and NiMH, and the failure mechanics of lithium cells can be dramatic.

All hail the Great Capacitor Brand Finder

Reply 8 of 9, by PCBONEZ

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A 3.6V NiMH pack from a cordless phone can be used as a direct substitute for the barrel battery. It's also relocatable, so you can place it away from everything sensitive if it ever fails.

Agree.
All of my phone packs as far back as I can remember have been lithium. Didn't even occur to me that they are still making NiMH packs for phones.

I'm not averse to lithium cells, but the behavior of lithium batteries under charge is quite different from NiCd and NiMH, and the failure mechanics of lithium cells can be dramatic.

If I didn't know this has been done by a few folks without issue I wouldn't have suggested it.
[Speculation] The 'chargers' in the old PCs are basically just resistor/diode dividers to the rail. (No IC controllers AFAIK)
[Speculation] IOW they are sufficiently "dumb" not to cause problems like 'smart' charges can.
I did used to, but I no longer think it matters what kind of rechargeable is used in that application.
.
I do like arrangements where I don't have to pull out the board and soldering gear just to change the battery.
.

Last edited by PCBONEZ on 2018-04-28, 07:07. Edited 1 time in total.

GRUMPY OLD FART - On Hiatus, sort'a
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Reply 9 of 9, by gdjacobs

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PCBONEZ wrote:

Agree.
All of my phone packs as far back as I can remember have been lithium. Didn't even occur to me that they are still making NiMH packs for phones.

I actually found some NOS NiCd packs to use, but I know recommending those will be a non starter in some parts of the world.

PCBONEZ wrote:
If I didn't know this has been done by a few folks without issue I wouldn't have suggested it. [Speculation] The 'chargers' in t […]
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If I didn't know this has been done by a few folks without issue I wouldn't have suggested it.
[Speculation] The 'chargers' in the old PCs are basically just resistor/diode dividers to the rail. (No IC controllers AFAIK)
[Speculation] IOW they are sufficiently "dumb" not to cause problems like 'smart' charges can.
I did used to, but I no longer think it matters what kind of rechargeable is used in that application.
.
I do like arrangements where I don't have to pull out the board and soldering gear just to change the battery.
.

Good to know that this has been tested. I wouldn't want to put my 386 board into harms way.

All the same, mount an XH pigtail and your world can be easy plugging like a cordless phone too.

All hail the Great Capacitor Brand Finder

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