VOGONS


First post, by butjer1010

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Hi, i bought 486 motherboard A-Trend ATC-1442G, but someone torn out all the electrolytic capacitors from board. I don't know if the board is good or not, but i don't want to throw it away before i try to fix it. I would be very grateful if someone has the same motherboard, and if he could tell me what are the values of them, so i can solder new ones. I have found only one picture of this board on the net, but it is impossible to see the values. One of the picture is mine board, without capacitors, other one is the one from net, the one with all the capacitors.
Many Thanks in advance!

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Reply 3 of 20, by butjer1010

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majestyk wrote on 2022-06-06, 08:43:

10 - 22µF 25V should be fine at all the positions.
The x-tal at the oscillator chip is missing also.

Wooow, You saw that, and i didn't! Thanks, i will solder capacitors first, and i will try to find same oscillator as on picture. 16.??? I cannot see the whole number.

Reply 5 of 20, by butjer1010

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majestyk wrote on 2022-06-06, 08:43:

10 - 22µF 25V should be fine at all the positions.
The x-tal at the oscillator chip is missing also.

Is it good to solder some "close value" oscillator there, or it has to be exactly the same? I cannot see the number, as far i can see it is 16.3C55?? To blurry...

Reply 7 of 20, by butjer1010

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majestyk wrote on 2022-06-06, 10:58:

The oscillator quartz will probably be 14.7456 MHz.

Thanks a lot, i will try to buy it and solder all of this components, and i will let You know if it's working.
Thanks again!

Reply 8 of 20, by snufkin

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Wouldn't the usual crystal be 14.318? The SC462 datasheet is here: https://www.datasheetarchive.com/pdf/download … am%2520circuits

It's only 3% difference, so I don't think it'll cause any problems either way.

Reply 9 of 20, by SSTV2

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14.318mhz reference clock is a must for all chipsets, even to this day, anything lower or higher will desync all timers in the system. You should first populate that xtal and test mb before proceeding with restoration.

Reply 10 of 20, by butjer1010

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snufkin wrote on 2022-06-06, 16:54:

Wouldn't the usual crystal be 14.318? The SC462 datasheet is here: https://www.datasheetarchive.com/pdf/download … am%2520circuits

It's only 3% difference, so I don't think it'll cause any problems either way.

I already order 14.7456 from ebay. So You think it will work even with this one?

Reply 11 of 20, by butjer1010

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SSTV2 wrote on 2022-06-06, 21:19:

14.318mhz reference clock is a must for all chipsets, even to this day, anything lower or higher will desync all timers in the system. You should first populate that xtal and test mb before proceeding with restoration.

You think i will not have a working MBO with 14.7456?

Reply 12 of 20, by SSTV2

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It would start, but don't expect proper operation from it. By the way, these 14.318M xtals are very common, you can find them almost on all video cards/motherboards. Local electronics stores would also have them at hand.

Reply 13 of 20, by butjer1010

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SSTV2 wrote on 2022-06-07, 21:49:

It would start, but don't expect proper operation from it. By the way, these 14.318M xtals are very common, you can find them almost on all video cards/motherboards. Local electronics stores would also have them at hand.

Thanks man, i will search for one of them. Will let You know if it's working, after soldering all the missing stuff 😀

Reply 14 of 20, by butjer1010

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butjer1010 wrote on 2022-06-08, 11:47:
SSTV2 wrote on 2022-06-07, 21:49:

It would start, but don't expect proper operation from it. By the way, these 14.318M xtals are very common, you can find them almost on all video cards/motherboards. Local electronics stores would also have them at hand.

Thanks man, i will search for one of them. Will let You know if it's working, after soldering all the missing stuff 😀

For now everything works, now it is time for testing other components 😀
Thanks a thousand times!!

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Reply 15 of 20, by butjer1010

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snufkin wrote on 2022-06-06, 16:54:

Wouldn't the usual crystal be 14.318? The SC462 datasheet is here: https://www.datasheetarchive.com/pdf/download … am%2520circuits

It's only 3% difference, so I don't think it'll cause any problems either way.

It works, thanks a lot!

Reply 16 of 20, by butjer1010

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majestyk wrote on 2022-06-06, 10:58:

The oscillator quartz will probably be 14.7456 MHz.

I solder 14.318 as everybody else were suggesting, and it works. Thanks a lot man, capacitors are perfect.

Reply 17 of 20, by butjer1010

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SSTV2 wrote on 2022-06-07, 21:49:

It would start, but don't expect proper operation from it. By the way, these 14.318M xtals are very common, you can find them almost on all video cards/motherboards. Local electronics stores would also have them at hand.

I cannot install windows or dos on that machine! I tried 3 different isa ide controllers, 4 different hard disks, 2 different memories, but it always stops on some point. What could be the problem i don't know, but maybe i will try to solder 14.7456 xtal, just to see if will work better?
I have one disk with dos 6.22 on it, but it wont load every time. Sometimes stops at "himem is testing extended memory", sometimes loads dos perfectly??? Weird....

Reply 18 of 20, by majestyk

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The correct frequency of the oscillator is 14.318 MHz as snufkin pointed out. The datasheet is always right 😀

I think your current problem has some other cause. Did you try installing DOS or WIN with all 9 cache chips removed? Is the cache jumpering 100% correct?
Same goes for the CPU voltage jumpering.

Reply 19 of 20, by butjer1010

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majestyk wrote on 2022-06-11, 16:23:

The correct frequency of the oscillator is 14.318 MHz as snufkin pointed out. The datasheet is always right 😀

I think your current problem has some other cause. Did you try installing DOS or WIN with all 9 cache chips removed? Is the cache jumpering 100% correct?
Same goes for the CPU voltage jumpering.

CPU voltage is ok, 3.3V (intel DX4 100, but it works at 120MHz - with cooler), but i didn't tried installing without cache chips. Thanks, i will try without them and see the outcome.