Atari Tetris board - schematics? I blew it up.

Peale

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I have an Atari Tetris board that I just blew up. I hooked it up to a Zenith monitor and when I went to hook up the ground/sync pins something fizzled. When I metered the pins after it was outputting 14VDC on one pin and almost 30VDC on another!

I only see one chip that's possibly bad, there's a small spot of what looks like epoxy on one leg coming out from under the ceramic. It could have been there before for all I know. Otherwise the board visually looks okay.

If I can get a schematic I'll start following it backward to see what goes where.
 
Just follow the pins back from the edge connector and replace the chips they go to... if that's not it then you'll have to dig further.

BTW: 14v??? 30v??? Are you running a monitor that needs an isolation transformer without one?
 
Just follow the pins back from the edge connector and replace the chips they go to... if that's not it then you'll have to dig further.

I tried tracing the traces back to their respective chips, but often I found no trace! I'm guessing this board uses traces that go between the layers.

BTW: 14v??? 30v??? Are you running a monitor that needs an isolation transformer without one?

Of course not! I always put any monitor on my test bench on an iso whether it needs it or not. This is some oddball Zenith branded monitor. There are several harness pins on it. I foolishly assumed that the three pins next to the obvious video connector were sync. Nope.
 
Can someone with a board do me a favor? The 7406N by position E, when I was removing the chip I slightly damaged the trace to position 1 of the chip. I can't tell if it also connects to a thru-hole directly underneath the chip or not. Currently pin one has what appears to be three traces coming from it; one leading to a bank of resisitors, one to the thru-hole beneath the chip, and one passing under the chip next to it.

Hope someone can help!
 
Sorry - my router crapped out and I just got back online. Looking at my board, the trace running between pins 1 and 2 ONLY go to that feedthrough, and not to pin 1 of the chip. Pin 1 only runs to that resistor bank.

Hope this helps.
Don
 
Yes - verified with a voltmeter. Here is a pic showing trace running between the pins.
 

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Thanks mate, very appreciated.

I have absolutely no idea how that trace got over to where it is, but I'll correct it now.
 
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