RE: Major Havoc - No Display, Plays Blind

Andy,
 
For starters, when you say that you have no video, do you mean you have no
output on BOTH the x and y outputs, or do you have a failure on only one
side? Given what you have replaced, you've replaced chips in both the
digital world in the vector generation side, and the analog world in the
video output side.
 
What you need to do is isolate the problem so that you know where to focus.
That is, does the board generate the vector data and present it to the DACs,
or not? If the data is there and the end result is "no video", then you
know you have a failure in the analog video circuit. You'd solve the analog
problem first, and then you might find that you have problems in the digital
domain as well. If the data is not at the DACs, it would not have helped to
replace all those chips in the analog section (yet) since they will not help
bring valid digital data to the DACs no matter what you replace there.
 
Troubleshooting the analog section is fairly easy. You can follow the
signal from the DAC's all the way off the board with a scope. You may have
a bad trace that simply replacing a chip will not fix. You really need to
trace each signal along the path through the analog switches and the
op-amps.
 
Troubleshooting the digital section is more complicated (depending on what
test equipment you have access to!) since with just a scope or a multimeter,
you can find pulsing digital data easily enough, but knowing if it's the
correct sequence of bits is something else. I'd say that before anyone gets
into a good description of how to troubleshoot anything on the digital side,
it would help to know if that's really where the problem resides. Then
others who have worked on MH specifically will jump right in, I'm sure.
 
Joel-
 
 
 
 

-----Original Message-----
From: Evrovski, Andrew [mailto:andy@cyberplex.com]
Sent: Thursday, November 02, 2000 9:31 AM
To: 'vectorlist@synthcom.com'
Subject: VECTOR: Major Havoc - No Display, Plays Blind

Hello Folks,

        I have a pesky Major Havoc board that refuses to give me any video.
I have replaced all chips in the video output section (AM6012, LF13201,
TL082CP, TL084CN, DAC08CN) as well as the transistors Q6 & Q7 (linear
scaling section of circuit). I am pretty much at a loss here. I thought
replacing those buggers would work, but alas, no success. All other
socketed chips have been brought over from a working board, so all RAMS,
ROMS, CPUS, AVG - 13379-?? chip (AMI), POKEYS, ATARI Custom Chips, -
literally everything that was originally socket plus the newly socketed
chips mentioned above are working chips).

        The game plays. I can pump credits, click the start and audio kicks
in proper sequences and the game plays... blind. Where do I go from here?
I am definitely at a loss for my next step and any help would be
appreciated.

Cheers
/\A\n\d\y/

Andrew Evrovski
Development Director
Cyberplex Atlantic, Halifax, NS
(TSE:CX)

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Received on Thu Nov 2 11:28:45 2000