Tempest resetting problem

I've been trying to fix a tempest board, but I can't seem to figure out
what the problem is. When I power the game up is just keeps beeping and
the 1&2 player lights just blink. When I put the game in test mode it
does the same and then when I ground the WDDIS is doesn't beep is just
sustains a long tone. Obviously a restting problem.

The roms are good and the Mathbox board is good. The clock is ciruitry is
good (Feedback loops seem to look good on the scope). All the voltages
check out fine.

The two things I'm suspect of are 1) The watchdog circuit: even though the
circuit looks fine on the scope, I can't help but think the problem lies
in this circuit

2) I'm not so sure of the ram. My fluke 9010a can't do a read/Write to
anything in the ram address space (both program ram and color vector ram)
- so either one of the buffers is bad or a ram chip is bad.

Perhaps someone could give me ideas? Sometimes I have a tendancy to
overlook obvious things.

Thanks...

Matt
 
Received on Mon Oct 18 03:07:25 1999