Re: Troubleshooting for Omega Race?

Id like to chime in here, although it is of topic. I have found the same
problem to be true for MCR games as well (tron, DOT, Tapper,etc) Power
measuring good in and good out of the linear supply, but scoped show too
much ripple for the CPU to run. Nine times out of 10, When Pulling the
caps I find them bloated on the top, (where you cant see them until you
take the whole thing apart ) or pissing out the relief valve on top. As
a rule of thumb, I replace them whenever A new machine enters the shop
regardless. Food for thought.

-=Mark=-

Chris Starr wrote:

>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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>
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>>
>
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Received on Mon Oct 7 07:27:11 2002