Re: Battlezone display woes

Hyperion wrote:

>Hello all.
>
>I have a Battlezone with no activity on either of the X or Y outputs.
>
>The AM6012PC's both seem to be taking input along the various lines
>(high/low pulsing), but pin 18 (I think that's the main output line) has
>no activity at all.. on BOTH of the AM6012's.
>
>The 7815 and 7805 on the board were both shot, and it had a popped cap on
>the 7805 feeder, and that's the one that produces the +5 DAC for the DACs,
>so I thought some power surge or whatever might have killed those DACs.
>
>However, I replaced one of the AM6012's, and still have the same problem
>-- still no activity off pin 18.
>
>Is pin 18 the right pin to check for output from the AM6012's?
>
>Any other suggestions?
>
>Thank you all in advance.
>
>Eddie
>

Pin 18 SHOULD be zero volts, it's a CURRENT output and the opamp it
connects to should cancel the current, hence no voltage.

You have a problem that's common to both channels so look to a common
source, in this case the voltage reference on pin 14 of the AM6012s..
 This is probably zero volts in your case and could be caused by an open
Q3 (or Q2) or a shorted C44. The DAC-08 at location C9 could also cause
it, if it's in a socket try running the board without it (UNHOOK THE
MONITOR FIRST!).

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Received on Sun Mar 2 00:42:38 2003