Tempest Analog Generator Question

 I'm trying to figure out a weird issue on a tempest board in the AVG
Section. The game is running blind and I traced the fault down to
the outputs (pin 2 and 15) of both LF13201 analog switches.

 I've put the schematic here and dotted where the good/bad signals
are. http://games.rossiters.com/images/Tempest.jpg

 I'm not exactly sure why both the X and Y section have the same
fault. The one chip they have in common within that circuit is the
74LS04 Inverter at J11 - but replacing that didn't help. They both
are getting +/- 15 volts like they should. The +15 regulator was
replaced so I'm thinking that maybe when it blew it took out both
analog switches. I had to order some replacements, but I'm still not
100% certain they both went bad. It might be something else I'm not
seeing.

 Does anyone have any idea why the output on pins 2 and 15 of both
analog switches would not work when they are getting proper inputs?

 Thanks....

 Matt

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Received on Sun Dec 2 21:37:41 2007