Re: Troubleshooting for Omega Race?

Found the problem ---

The two large caps (100000mfd and 50000mfd) on the filter assembly before
the linear supply were BAD (almost burst open). They were causing a 2volt
sag every 8 to 10 ms which was putting the CPU into an endless reset
state!!!! When tested with no load they appeared to be fine, put a load on,
and everything goes to hell. I swapped these out, and VOILA! Instant Omega
Race. I would strongly recommend people replace these before testing "dead"
boards. If you see spike or sag points roughly the same frequency (8 - 10
ms) on your +5 voltage, then it's definitely this problem.

I am now a proud owner of a completely fixed and bulletproofed Omega Race
cocktail now.

----- Original Message -----
From: "Chris Starr" <cstarr@speakeasy.net>
To: <vectorlist@synthcom.com>
Sent: Friday, October 04, 2002 7:34 AM
Subject: VECTOR: Troubleshooting for Omega Race?

> Does anyone have a flowchart for troubleshooting an Omega Race PCB?
> This board I am working on has no acid damage, but is basically DOA.
>
> Here is what I have done:
>
> 1) Replaced all 2114 ram chips with a test set of known good chips. (I
still
> have the originals)
> 2) Checked the A/D chips for functionality. (They're fine)
> 3) Monitor is good, It's a Wells Gardner 15" XY . I tested it with my
> battlezone with no troubles.
> 4) Daughterboard seems to be ok, I can monitor input pulses from the
rotary
> encoders, and push buttons, along with the test switch.
> 5) The power supply is A-OK. It's putting out clean and correct voltages.
> 6) All roms chips have been verified to be good by checking their crc on
an
> eprom burner.
>
> I have a logic probe, and have started to pick my way through the board
> looking for trouble spots, but need to ask if anyone has expertise in
where
> some
> typical problem areas are to look at first. I also have an HP 5005A
> signature
> analyzer at my disposal if anyone has any recommendations on setting it up
> so that the z80a runs a NOP loop.
>
> Any suggestions??
>
> Thanks
>
> c-starr
>
>
>
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Received on Fri Oct 4 23:31:44 2002