RE: Major Havoc - No Display, Plays Blind

There are a lot of different things to check in the VSM :) Check for 12Mhz
on the latches that feed the DAC's (ex pin 11 on 8B). Check the inputs and
outputs of 7C (demultiplexor). Change out the vector ram, change out the
vector generator address controller (7E/F). Hell, change out all of the
socketted chips in the vector generator :) As long as you have a working
board there, this should be easy enough to do.

Also check out the halt flag. Maybe the only reason the game plays blind
is that the CPU isn't waiting for the AVG to finish. If it is ok, its a
positive piece of information. Usually the VSM fails in such a way the
game does not play blind. This means that your problem is most likely with
the output of the VSM and not the internal processing.

You may want to go to shit shack and pick up a cheap logic probe (~$10).
It is a cheap way to to test pins for activity quickly.

Jon

warning: i am not an electrical engineer.. none of my opinions are based on
reality :)

At 05:02 PM 11/2/00 -0500, you wrote:
>>>>
Thanks for your advice (and everyone's input).
  
To clarify, what I see is a steady minimal voltage on both X & Y loops
(around 0.6 - 0.9 VDC) steady... (I tested a working board X&Y and have
seen what things SHOULD look like and I am not seeing anything like that on
this board).
  
When I turn up the birghtness to bypass spotkiller, I get a diagonal line
about an inch in length. I adjusted the y-cntr pot and the line moves up
and down (I used part of the Tempest theory of operation to get that far).
After that point, it looks like it's a VSM-fault (maybe it's different for
MH), but I am not armed with anything other than a Fluke 867B Graphical
MultiMeter.
  
A>
 -----Original Message-----
From: Rosenzweig, Joel B [mailto:joel.b.rosenzweig@intel.com]
Sent: November 2, 2000 11:56
To: 'vectorlist@synthcom.com'
Subject: RE: VECTOR: 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 22:32:37 2000