Re: Need Guide to Tshooting Asteroid boards

Keith,

I posted this a couple weeks back, it should help.

To: vectorlist@mcfeeley.cc.utexas.edu
cc:
Subject: Re: Major Havoc help (was: Vectrex on Vector Monitor?)

My contribution to the Vector Fix-it FAQ,,, :')

For Asteroids and Asteroids Deluxe boards with no signs of life:

Unplug the monitor from the harness at it's molex connector to avoid
damage to it - when the monitor sits in spot killer state too long things
can fry!

1. Start out by verifying that the clock is running. (The crystal on
these boards
breaks off WAY too easily.) Then check that the CPU and ROM's are good.
If you found nothing or it's still dead, you've got a watchdog reset
happening - see if pin 40 of the CPU is toggling (it's supposed to be held
high).

2. To figure out who is causing the watchdog resets (the MPU or the VSM
(Vector
State Machine)), take the 74LS42 at L5 (L6 on Asteroids) and socket it,
then
lift out pin 1 to isolate DMAG0.
a) If the board stops resetting, the MPU is not the problem and you
should be
able to play a game "blind" or switch into test mode and listen for any
beeps
indicating RAM/ROM problems. That will at least help you get the MPU side
running properly and then you can play the game blind.
b) A board that is still resetting has a problem with the MPU and also
possibly
the VSM. Check the ROMS, RAM and especially the 74LS245 (or AM83048)
at E2 (E3 on Asteroids). Once you fix the reset problem, switching to
test mode
should reveal any other missed RAM/ROM issues and verify the MPU is
running ok. You should now be able to play the game blind.

3) Place pin 1 of the 74LS42 (DMAG0) back into it's socket. If the
watchdog is
resetting, it's time to look at the VSM side of things. If it's not
resetting, plug
the monitor back into the harness and look for some video.

For the VSM, check the PROM at C8 (C9 on Asteroids) and surrounding state
machine signals for HALT, DMAGO, STOP, GO and the like. The rest is pure
grunt
work to check the state machine is running properly. Someone else please
feel free to add details to the VSM debug procedure...

Paul

Keith Sink <KeithS@onyx.com> on 11/11/98 06:47:40 PM

Please respond to vectorlist@mcfeeley.cc.utexas.edu

To: vectorlist@mcfeeley.cc.utexas.edu
cc: (bcc: Paul Tonizzo/SYBASE)
Subject: Need Guide to Tshooting Asteroid boards

Can anyone give me a guide to diagnosing problems on an Asteroids board? I
have two. One seems to have a broken trace that I'm going to have to track
down. The other does some beeps and the counter begins clicking away. No
game sounds or video.

All I have for diagnostic tools is a digital volt meter.

Any advice and guidance is appreciated.

-Keith
Received on Thu Nov 12 07:53:01 1998