Re: Battlezone Half Screen, please help if you can

Still no joy?

Can we assume that theAVG - XY outputs look fully bipolar on a scope,
before they get to the monitor?

I would think that <2mV of psu ripple is ok, and certainly not the real
half-screen fault.

If you are sure it is the Z-output have you looked at the window clipping
circuit? you say that p12 of B7 is HLP (is that high-low pulse?) and you
say it should be both be high, well in this case, the clipping circuit is
clipping when it should not, so suspect that either H10 faulty, or analog
switch D11 faulty. If you have socketted B7, just force /ZBLANK high and
see what you get.

I have had a BZ with faulty Analog switches, (D11) sample-hold voltage
following op-amp (C11), comparators (B12, D12) and even faulty input
protection diodes (CR3-CR10). Suggest you just isolate the clipping
circuit and take it from there...

Or even just pull the Z connection from the Edge connector or monitor
cable harness or connector, then you will know if it really is Z blanking.

Good luck - Tim.

PS: Do post your successes - Thanks.

MKDUD@aol.com
Sent by: owner-vectorlist@synthcom.com
26/02/03 21:35
Please respond to vectorlist

 
        To: vectorlist@synthcom.com
        cc:
        Subject: VECTOR: Battlezone Half Screen, please help if you can

     I still have a half screen on this BZ AVG board. Problem has to be in
the Z section, but I am stuck trying to track it down. Board is in test
mode, boots fine, no errors.
     ZBLANK is HLP (pin 11 B7 LS86). I also found that pin 12 of B7 is
HLP. This should both be High. Pin 13 is low, as it should be. Replaced
B7, C7 (LS174), P9 (LS164) and N9 (LS02). Also replaced Q7 (3906), Q8
(3904), and Q9 (3904). Still have the same trouble.
     Also, is 1.8mv of AC current OK on my +15 line? I checked the AC
ripple on a working AVG, and it is down around .3mv. I didn't think this
would cause my problem, though.
     Any further help would be appreciated.

Thank You,
Michael Kelley

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Received on Thu Feb 27 14:55:00 2003