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um4981 Based MotherBoard components

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First post, by ChrisXF

Posted on 
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Hi everyone! Long time lurker, first time poster!

I'm currently trying to revive a um4981 motherboard that I found in the back of a cupboard in my hardware lab. It's missing a few components, and I'm wondering if anyone could help?

I know there's not going to be a schematic of BOM anywhere probably, but the parts I'm missing should have readable numbers on if anyone has one of the boards and wouldn't mind checking?

Ok, here's the board:

IMG_20210129_120007.jpg
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IMG_20210129_120007.jpg
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And my specific query would be, what transistor and crystal are missing here?

IMG_20210129_120010.jpg
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IMG_20210129_120010.jpg
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216 views
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Fair use/fair dealing exception

I'm thinking it's probably just a standard watch type crystal and maybe a generic TIP31C or equivalent transistor?

If anyone could check that would be awesome - every picture of this board I've found has the parts obscured by a heatsink, 🤣.

Thanks so much,

Chris...

Reply 1 of 2, by Deksor

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You should be able to start the board without that transistor in place, it's required only for the 3.3V CPUs.

I see that you're also missing a "P9436ZL" chip next to the cache
The crystal seems to have nothing written on it http://www.win3x.org/uh19/motherboard/show/2127

Make sure you configure your motherboard properly as well.

Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 2 of 2, by ChrisXF

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"P9436ZL", they are the three or four 74f256 chips that have been (very carefully, thankfully!) removed from the board, along with some inductors and one or two surface mount resistors. I've put new ones back on 😀

I notice there's no cache - and no jumper option for no cache, so I think I'm going to need to try and find the cache chips and the TAG RAM. I can see those quite clearly from the pics on Win3x though so that's good. High res pictures are awesome, kudos to whomever made that entry!

I will leave the transistor off to begin with as suggested, I think my CPU is 5v or I can find one that is to test. I'm about 99% the crystal missing is a standard 'watch type' crystal so I've replaced it with one to test. I have some SIMM sockets to replace and a few other wee bit of rework then I can actually power this board up with every part of me that can, cr0ssed!!

Thanks,

Chris...

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