Re: Battlezone self test problem

I agree with likely bad VSM, and probably right at the front end of it since it draws nothing or practically nothing. Maybe none of the AVG control signals are working.

Best guesses are the major VSM / AVG signal decoders

- bad latch (74LS175) atL K8, J8
- custom BPROM K7 plus J7 (74LS42 4-line to 10-line decoder) generates /strobe0,1,2,3 and /latch0,1,2,3
- J10 - (74LS74 dual D-FF) pin 6 = signal /NORM
-check activity of signals OP0, OP1, OP2 entering BPROM K7 pins 1, 2, 3 respectively.
-check activity of signals /Strobe# and /Latch# signals coming out J7 pins 1,2,3,4,5,6,7,9

Other possible bad ICs mishandling drawing data, generating bad DVY data (so bad AVG PC values):
-bad shift register (74LS194) at
         D5, D6, C5, A5, A6, B5
-bad gate at:
         C6 (74S00), B6 (74LS14)

Sometimes a bad IC runs warmer than the others of its same type so feel around or use a laser temp gun. Maybe you'll get lucky.

William Boucher
http://www.biltronix.com
  ----- Original Message -----
  From: Kevin Moore
  To: vectorlist@vectorlist.org
  Sent: Friday, December 23, 2011 7:08 PM
  Subject: VECTOR: Battlezone self test problem

  've got a new one.

  Ran fluke long and short ram tests good.
  Rom signature tests come back good.
  Tested aux board with good main no problem

  Game coins up, plays, but graphics are all screwy.
  Put in Test and get one long continuous tone before watchdog kicks in.

  Manual states a long low tone will be present when Vrom B/C3 is bad.

  Have swapped both Vroms, and even tried the highscore kit. Still can't get test screen to come up.

  Based on the fact the game does play, I'm guessing it's in the VSM area somewhere.

  Any pointers?

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Received on Fri Dec 23 23:19:40 2011