Tempest no video signal

Zinfer

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All voltages are good. Tempest hooked up to a PAT. Game plays blind. No AC voltage at X or Y out and no signals on oscope. I tried piggybacking the TL082's as well as the A/B12 and 13 1495's. Nothing.
The board has a considerable bow to it. But as I said, game is playing - just no video out.
I've also swapped the mathboard with a known working. No change.
IMG_2996.jpg
 
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Got video going. But the colors are wacked. No Red, Yellow, Green. Any suggestions?
 
How did you fix video? Mine is playing blind also. Just curious. Wish I could help with your new problem, just a noobie here. Also, what is a PAT?
 
I found a broken trace at between K3 and K5 where someone before me had attempted to throw in a 2114 Ram. They'd burnt the trace in the process.
The Pat 9000 is designed to allow the technician to power up and test the operation of Atari coin operated video games without the game cabinet itself. It's handy to test and replace components while the board is on the bench. Alot of people tend to think it fixes boards by itself. --I beg to differ---
IMG_2169.jpg


IMG_2166.jpg

I replaced all the Q2-4 transistors as well as Q9 and 6. Still no change. I'm not seeing any trace problems so it almost has to be a 74LS IC.
 
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That looks like a handy little tool. Sure could use something like that as most of my problem games are Atari. Thanks for the reply and pics. Good luck.
 
BAD Tempest Vector Color Diagnostics (No Red, Yellow or Green):

IMG_3111.jpg


Good Tempest Color (What you should see)

IMG_3112.jpg


The images were shot from two different boards. The first is the bad board I'm working on. The second is a known good working.
 
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That's just funky. How can you have WHITE if you don't have decent R, G, AND B??

Maybe some color output transistors or something with the color bits of vector memory. I don't know how Tempest is setup as for how color goes.
 
That's just funky. How can you have WHITE if you don't have decent R, G, AND B??

Maybe some color output transistors or something with the color bits of vector memory. I don't know how Tempest is setup as for how color goes.

That's what has me completely stumped! I felt for certain it was the color output transistors, so I just replaced all 3. Afterwhich I got the sinking feeling...
I think I'm going to have to order me some piggyback materials.
74LS157 P8
74LS174 H8,N8
74LS164 A9
74LS399 H9
82525 P9 (--Don't think this is available anywhere)
All of which are contained in the Vector color management portion. I double checked the board for ANY trace problems. I guess I'll have to try and scope-trace back from the transistors of the known good board. It's moments like these I WISH VectorLabs already had those 74LS in-circuit testers available. That'd be darn-tootin nice right about now.
I almost feel like replacing Q10 for the hellofit but I don't believe that should do anything as it's not really used.

'Ah there's the bad chip' --plop in goes a socket and new ic.
 
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Ah..

Red looks like magenta,
Green looks like cyan,
Yellow looks like white.

Your blue is stuck ON somehow.

Stuck bit on P9 pin 9 maybe? You could desolder the P9 from both boards, add sockets and find out. You might be able to scope out the difference without removing the chips.

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I tried using the scope, multimeter and logic probe. Couldn't really see any discernible differences between the known good board and the bad. Kevin suggested removing P9 on both boards, socketing and then trying the known good P9. It fixed the problem. The problem was in fact a bad P9.
Still waiting on the replacement ic's to arrive I should have posted a followup on here. But yes, your right, apparently blue was stuck on all the time.
 
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