Faulty S3 805 VLB video card \ VOGONS

Faulty S3 805 VLB video card

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First post, by tony359

Posted on 2021-02-17, 19:54

tony359 Offline

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Hello all

As a "to avoid banging my head during lockdown" fun project, I sourced a faulty VLB video card. It shows the issue you can see in the video - this is the PC booting up so the flashes follow the two screens I would expect when booting up without a floppy attached. I have re-flowed all the solder joints - including the main chip, which unfortunately doesn't look in its best shape.

I was thinking of a memory corruption issue? I have replaced two of the chips but that did not fix it - I have other coming (those are JSOP directly soldered on the PCB so I'd rather not removing them again with hot air).

I was wondering if anybody had any suggestions?

As I said, this is a fun project, I totally understand that this card is not worth my time! 😀

Thank you!

https://youtu.be/eEjGfzOMXxA

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Reply 1 of 8, by Horun

Posted on 2021-02-18, 01:21

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What model Dell is that monitor ? Looks like it cannot sync properly, does the VGA cable have all 15 pins ?
And where is the heatsink for your AMD cpu? 😁

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 2 of 8, by tony359

Posted on 2021-02-18, 09:29

tony359 Offline

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ahaha heatsink is coming. I'm keeping an eye on that, don't worry. But thanks for spotting that!

I never had issues with that monitor and another video card works fine. This S3 was sold as "faulty" that's why I did not think too much of a monitor issue - I can try another one though. Yes, the VGA cable has all the pins. Monitor is a P2411Hb

My Youtube channel: https://www.youtube.com/@tony359

Reply 3 of 8, by GigAHerZ

Posted on 2021-02-18, 10:07

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What i've found is that the signal on those cards is very low. When i disconnected the 6 diodes near VGA connector, the picture became a lot brighter. But i have no solution for v/h sync signals. I had a LCD, that had also trouble recognizing that there is a proper picture and i blame the low signal level of v/h sync signals.

I have no oscilloscope to confirm that, but this is what i have figured out so far. Looks like the ramdac produces too low signal for some LCDs.

"640K ought to be enough for anybody." - And i intend to get every last bit out of it even after loading every damn driver!

Reply 4 of 8, by tony359

Posted on 2021-02-18, 11:02

tony359 Offline

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Uhm.. interesting. I do have a scope so I can compare the signals between the working card and the non-working card. I'll keep you posted, thank you!

My Youtube channel: https://www.youtube.com/@tony359

Reply 5 of 8, by quicknick

Posted on 2021-02-18, 12:21

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Also check the 14.318MHz crystal while you're at it, and maybe replace the decoupling caps with some of higher quality.

Reply 6 of 8, by tony359

Posted on 2021-02-18, 13:05

tony359 Offline

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I've compared the signals. The "faulty" card is actually showing higher signals than the working one. But most importantly I can "see" the corrupted picture on the scope - it's clearly flashing stuff while the working card has a completely different signal which is consistent with the text that appears on screen.
The junk signal comes out of the DAC.

I did check the crystal and I do have the correct frequency on the DAC indeed.

My Youtube channel: https://www.youtube.com/@tony359

Reply 7 of 8, by Tronix

Posted on 2021-02-18, 13:21

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For the successful operation of this video card, it is necessary to set the jumpers correctly (because they physically connect some memory lines).
Here is a description of the jumpers: https://stason.org/TULARC/pc/graphics-cards/U … VGA-S3-805.html
So, you need set JP5 1-2 and JP4 2-3.

https://github.com/Tronix286/

Reply 8 of 8, by tony359

Posted on 2021-02-18, 13:40

tony359 Offline

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OMG! It works!!!!

Thank you Tronix - I do not know why I didn't check the jumpers? It's usually the first thing I do when I get a "faulty" board and 50% of the times it's all it needs.
I believe I just didn't find the correct datasheet.

THANK YOU A LOT!!!

(Now I have lots of spare RAM modules!!)

My Youtube channel: https://www.youtube.com/@tony359

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