Re: Debuging wndwblk in battlezone

Thanks. That clue just gave me the kick I needed so that now the whole circuit now makes sense.

Have I mentioned that I HATE analog?

:)

David
  ----- Original Message -----
  From: MyPearl
  To: vectorlist@vectorlist.org
  Sent: Friday, July 04, 2003 9:03 AM
  Subject: Re: VECTOR: Debuging wndwblk in battlezone

  I would definitely try the opamps. Easy check, they are used as comparator, so the output is always VCC or GND, depending on which input voltage is higher, - input higher than + input will make the ouput is GND, + input will make the output go VCC.
    ----- Original Message -----
    From: David Shoemaker
    To: vectorlist@vectorlist.org
    Sent: Friday, July 04, 2003 11:21 AM
    Subject: VECTOR: Debuging wndwblk in battlezone

    Well I got the board running with the fluke. Looks like a bad 6502 socket was the culprit.

    Now I have a problem with the ZOUT. Hooked up to the scope nothing is being hidden.

    Going through things I verified that the appropriate signals are getting to the Z section of the outputs. But the ZN3904 @ Q8 is dropping it all to ground. I pulled Q8 and get normal Z function.

    Tracing back the input to Q8 I see that !ZBLANK controls it. This is in turn controlled by !WNDWBLK and part of the stat system.

    Checking !WNDWBLK I see that it is always low.

    Any ideas on how to debug this area? !LST & !HST which feed it appear to be working fine.

    I am betting some cap / resistor / diode / comparator / opamp in the X or Y section of the window hardware has died and is causing this but can't really see anything.

    David

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Received on Fri Jul 4 16:44:53 2003