Tempest Issue

wontwa

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Grand Rapids, Michigan
Picked up a "was working before I moved it, now plays blind" Tempest recently. Reseating the edge connector on the board got it to fire up, and it's playable - but the screen has some irregularities and was wondering where I should start.

Basically some of the lines on the boards are too long (or short), the screen image in general is too large, the words on the bottom of the screen are folded over, and when it shows the Tempest logo in attract mode it has a curve to it (and is definitely too large - you can see a slight burn in the monitor to where the regular size Tempest logo should be). I've reseated the chips on the board and replaced "big blue" and it made no difference.

Here's a link to 3 photos of the issue:

http://www.flickr.com/photos/38961212@N08/5114957205/in/set-72157625240906300/

Not sure if I should be messing with the X Y settings on the board or looking at other issues?

Thanks!
 
Start by putting it into test mode and the cross hatch screen. Then adjust the X/Y pots on the board to get the pic as good as possible. Then let's see where you're at...
 
Adjust the "BIP" pots ["BIP" stands for "Bipolar." The BIP pots provide the offset current to convert the Unipolar DAC to one that provides a Bipolar output]: Adjust the XBIP and Y-BIP so that the corners of the diagonal lines rest exactly on the sides of the outer rectangle. [NOTE: It is easier to advance to the screen with the single large cross-hair on it to make the BIP adjustments; just make sure the lines meet at exactly the center. Using the cross-hair screen, you should try to make the screen look like a giant plus sign. Be careful when joining the lines in the middle that you do not overlap; it is VERY hard to notice this. You might want to make a big gap (go the wrong way) and then converge until the two segments just touch.
 
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