Tempest Stretch (right side only)

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Hi;
I am working on a Tempest that was DOA.
I believe that without a clean source of power, you dead in the water so I rebuilt the power brick and A/R II, tested the voltages, hooked everything up, retested the voltages on the board and..... viola` I got game!
So I'm all patting myself on the back and then .....

http://www.youtube.com/watch?v=Z5L8xmH13N8

http://www.youtube.com/watch?v=uYSpI4mBtdU

http://www.youtube.com/watch?v=lds335o1QVQ

Any suggestions, (keep it civil;)??

Thanks in advance
Jeff
 
Wow. I can honestly say I've never seen that. I suspect it's a monitor problem, not gameboard. It looks like the picture is trying to collapse every few seconds so I'd suspect HV regulation to be a problem. The stretch would seem to be a deflection problem. Something like a bad cap or resistor in the VERTICAL deflection circuitry. I suppose if the HV is not being regulated correctly, it could cause a weakness in the vertical deflection to show up. Have you check the B+ voltage for fluctuation?
 
That'a a very good idea, thanks.
I'll hook up a HV probe and see what it's doing.
I'll post the results.
Jeff
 
GOOD CALL!!!!!

I just hooked up my HV probe and got a whopping 11kV

I'll probably just rebuild the entire monitor to make sure.

Thanks again
Jeff
 
I've never seen one side go crazy like that from low HV... so there may be two problems. There definintely appears to be blooming going on, which as you noticed, is caused by low HV. For that, I'd suspect ZD902, as that's commonly bad. BE SURE YOU REPLACE ZD902 AND NOT D902!!! Lots of people mistake those two and fry all kinds of stuff. Other than that, yeah... I'd do a rebuild and go from there.

DogP
 
I swapped the monitor with a known good working for testing before I did the complete rebuild and "you are corrent sir!" (use Ed McMahon voice over), there is a board problem as well.

Once the game heats up, about 3-5 minutes, it starts so there is an IC on it's way out. I guess I'll have to get the freeze spray out, any ideas on where to start?

Thanks
Jeff
 
Where to start

Yup.

You have a problem with your X vector output circuitry losing linearity.

#1 suspect is a scratchy linearity pot. It's usually siliconed in place but you might need to turn it back and forth. Use a mirror so you can look at tge screen while you tweak it. If that's not it, it could either be the DAC or the op-amp or driver.
In this case I would not suspect just the ICs but any of the discrete components in that part of the analog output section.

Have you ever bumped any of the linearity pots on the board?
I regularly (once a year) have to exercise the x-size and y-size pots or my image jitters around.
 
That's an excellent idea, and pretty easy as well. I'll start with that, once I get a minute, we are having a party and there is a lot of "stress" in the housed and I don't think I'll get the chance to try it today......
Thanks again for the hints and have a Merry Christmas (PC-happy holidays).
Jeff
 
Ok, I've got some time on my hands over the break.
I pulled up the schematics and did some checking.

Its almost for sure NOT your linearity pot.

First check the +/- 15V supply on the board. The analog op-amps use this. Your Y channel is good so this is not really likely to be it, but first things first.

There's a finger on the edge connector of the aux board which will turn your machine into a cocktail when grounded. It is Finger C, Gnd is A. Connect these two fingers and you will have a cocktail minus the second set of controls. If you can't get to the harness you can do this on the board with a jumper wire. Locate the common trace between R68 and R43 and run a jumper to the large ground bus encircling the board.

Play a two player game in cocktail mode. When the screen inverts for player two, observe the anomaly.

1) if the anomaly goes to the left side of the screen it's either the TL082 at A11, or the DAC at A10. Your DAC might be at B10.

2) if the anomaly stays on the right side of the player two inverted image then it's either one of the MC1495 located at C12 and A/B13 or it's the TL082 at D/E12.

Good luck.
 
Hey man, thanks for the precise troubleshooting flow chart, I will check this out ASAP, most likely in a couple of days and I have Family obligations at the present and there is no way I will be allowed into the shop.
Have a Merry Christmas.
Jeff
 
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