jumping subsequent vectors - Omega Race

Hi all,

I am finishing up the reproduction main board for Omega Race and after finding a few missed traces both the program and vector sides are running. I have two problems remaining: self test passes all but the darned BBU RAM, and I have jumping vectors:

http://www.gauck.com/arcade/reprOR/testing/IMG_4042.MOV

Drawing was better (but not perfect) up until the time I was testing voltage at RAM H1 and slipped. Killed one of the VROMs. Interesting problem, easiest to analyze on a text screen... the first letter in the line of text is fine, then as more vectors are drawn they get further out of alignment. And they move - not a static misalignment - jumping up and down and side to side. Does it with graphics and on the test screens but to a lesser extent (since there are fewer vectors in test).

Seems as if when the state machine first loads new coordinates, all is well, but then starts losing track of where the beam is.

I swapped out all RAM, the latches (273s), the multipliers (7497s), counters (191s), the multiplexers (157s), and the flip-flops (374 / 174s). Yay sockets. It sure seems digital to me, but what's left?

The BBU would also be nice to solve. It doesn't work on any of my original boards either. Haven't really dug into that one but if anyone has one that does work, is the battery required in circuit to pass self-test?

-Douglas---------------------------------------------------------------------------
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Received on Fri Aug 31 11:46:16 2012