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|                   Q*BERT SYNC INVERSION HACK                  |
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COPYRIGHT 2001

REVISION NUMBER: 1.0
  REVISION DATE: 04 JUNE 2001
     CREATED BY: Al Kossow and Joe Britt



STANDARD DISCLAIMER:
--------------------
REMEMBER, NO WARRANTEES, EXPRESS OR IMPLIED, ARE GIVEN.  USE THIS
INFORMATION AT YOUR OWN RISK.  I AM NOT RESPONSIBLE FOR ANY DAMAGES
THAT MAY OCCUR TO YOUR PERSON OR PROPERTY.


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GENERAL OVERVIEW:
-----------------

From: Al Kossow (aek@spies.com)
Subject: trivial QBert sync inversion hack 
Newsgroups: rec.games.video.arcade.collecting
Date: 1998/10/13 



Joe Britt and I came up with a trivial hack to convert Q*Bert
boards to negative sync, and lets you generate combined H/V
sync as well. It turns out that J14 (a 7407) is only used
as a sync buffer. Replace it with a 7406, which is an inverting
open collector buffer. The sync is then active low, and since
it is open collector, you can 'wire-or' the outputs and get
combined H/V sync.



ADDITIONAL INFORMATION:
-----------------------

       7406
    +---\/---+
 1 -|1A   Vcc|- 14
 2 -|1Y    6A|- 13
 3 -|2A    6Y|- 12
 4 -|2Y    5A|- 11
 5 -|3A    5Y|- 10
 6 -|3Y    4A|-  9
 7 -|gnd   4Y|-  8
    +--------+



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