Tempest playing blind

jb007gd

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Hello all,

I recently picked up a Tempest cocktail with a monitor that had blown F100 and F101 fuses. I installed an LV2000, did the Bob Roberts cap kit and additional parts package and resoldered the connectors.

I tried the monitor and the spot killer is lit. I cranked up the brightness and got this:

http://yfrog.com/0k20100326163214j

Not exactly a collapsed screen, but there is a clear line on the right hand side. Not sure what the faint rainbow colors in the middle mean. The screen changes around a bit but doesn't significantly deviate from whats in that picture.

I measured the voltages on the X and Y lugs on the game board and the Y is outputting a steady 10 volts. The X hovers between -.1 and .1 volts. There are two red LEDs on the game boards and they are both lit, but I'm not sure if that's a good or bad thing.

I flipped the test switch and powered the game up. The start buttons stay lit and there are no beeps. The game is set to freeplay so if I power up the game normally and press Player 1, I hear three beeps then the game starts and I can play it blind. Not sure if those three beeps are normal or not.

I'm thinking the monitor could actually be working now but it appears the board isn't putting out the vector signals to the monitor. I'm not afraid to try working on the boards but I have never done any board work before.

One thing I read while searching through the forums is possibly a bad MC1495 chip. Does this sound like a good next step and if so, can these be tested with a multimeter? (Because that's all I've got! :)

Thanks!

- Jay
 
First verify the monitor is fine. Do you have a good B+ (180vdc)? Can you measure good +/-28vdc (approx.) at the casings of the two transistors mounted on the side-wall to the right of the deflection board? If so, then I'd look into your Y output...
 
The neck socket looks okay, but the voltage measurements are a little off. The 3792 transistor measured -25.6 volts and the 3716 transistor measured 23.2 volts. I'm going to measure B+ at at pin 5 of P900 and will post the results...
 
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Yeah, that's fine. Hows the neck socket pins look? Also, check that big molex (both sides) on the deflection board. Sometimes the pins back out and don't make good connection...
 
Sounds like you have a "Y" problem, the "X" reading of +/- .1 indicates AC voltage, you shouldn't have 10V on the "Y" lug, you may have a blown TL082 amp at D/E13, you can follow the signal from the first amp (pin 7 of the TL082 at D7), then to pin 1, if either has a significant DC reading you will need a scope to get much further, it gets more involved with the MC1495 and the LF13201 switches.
Dick
 
Sounds like you have a "Y" problem, the "X" reading of +/- .1 indicates AC voltage, you shouldn't have 10V on the "Y" lug, you may have a blown TL082 amp at D/E13, you can follow the signal from the first amp (pin 7 of the TL082 at D7), then to pin 1, if either has a significant DC reading you will need a scope to get much further, it gets more involved with the MC1495 and the LF13201 switches.
Dick


Okay, I really want to try and do this but I might need some help. The chip at D7 doesn't look like a TL082. It's an Atari chip that says 136002 125. See pic here.

http://yfrog.com/jq20100327180405j

If this is okay, then great - I'll measure away. Just to make sure I am clear, I should be checking the voltage on pin 7 and pin 1 of that Atari chip on D7. My next question is what constitutes a significant (and therefore troublesome) DC voltage in this case?
 
Yeah, that's fine. Hows the neck socket pins look? Also, check that big molex (both sides) on the deflection board. Sometimes the pins back out and don't make good connection...

I pushed down on each of those molex pins and they didn't have much give to them. I think the neck socket pins look fine but I will post a pic later because maybe a second set of eyes will catch something I am missing. Thanks for your help! :)
 
I made a mistake. When I was measuring voltages on the X and Y lugs I was measuring DC current instead of AC current. I measured AC current at the big white molex connector that goes from the game to the monitor. I made these measurements without the monitor being plugged in. Now I am getting the following:

X: 0.0 volts steady
Y: Constant fluctuation between .4 and 2.1 volts

If I am understanding this correctly, it would appear the X deflection circuitry on my game board is hosed, right?
 
Okay, I really want to try and do this but I might need some help. The chip at D7 doesn't look like a TL082. It's an Atari chip that says 136002 125. See pic here.

http://yfrog.com/jq20100327180405j

If this is okay, then great - I'll measure away. Just to make sure I am clear, I should be checking the voltage on pin 7 and pin 1 of that Atari chip on D7. My next question is what constitutes a significant (and therefore troublesome) DC voltage in this case?

That's not the right location. He said D or E 13, not looking at a board or schematic so i dont know what one is X and what one is Y. A TL082 is 8 pins total, 4 on each side.

EDIT: just looked at my Tempest board, looks like D is X and E is Y. They are in the "silver section" of your board. They aren't socketed either so you will need a socket, unless someone put a socket in already .
 
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I would check the voltages on your 7915 and 7815 too before going any further. The 7915 is at the top of the "silver section" at location VR1 and the 7815 is to the right of it at VR3. Be careful that you don't slip and go across 2 legs at once. Going to have to use a clip or be steady, at the very least use a clip for your ground.

On the 7915 measure the middle and right legs.

Middle leg should read about -22VDC or close to it.
Right leg it should be -15VDC

On the 7815 measure the left and right legs.

Left should be +22VDC
Right should be +15VDC
 
Here are my results. It looks like the Y amp at D11 is bad, do you agree? If so, will simply replacing that TL082 and retesting be good enough or could there be more bad parts upstream that could burn out my freshly replaced TL082?

By the way, thank you all for helping me along. I can't wait to play some Tempest when this beast is all fixed up!



On the 7915 measure the middle and right legs.
Middle leg should read about -22VDC or close to it. (measured: -24.87)
Right leg it should be -15VDC (measured: -15.23)

On the 7815 measure the left and right legs.
Left should be +22VDC (measured: +24.56)
Right should be +15VDC (measured: +14.79)


the first "Y" amp is at D11, you should read less than .1DC on either pin 7 or 1
(Pin 7 fluctuates between +.8 to -.6)
(Pin 1 fluctuates between +.6 to -.7)


the "X" amp is at A11, you should read less than .1DC on either pin 7 or 1
(Pin 7 fluctuates between -.19 to +.06)
(Pin 1 fluctuates between +.2 to -.02)
 
I bought a new TL082 from Radio Shack to replace the (presumably) bad one at D11.

What's the story behind installing a socket when replacing an IC? Is that to make future replacements easier or is it a necessity whenever one is replacing an IC?

It appears the holes I would be desoldering are smaller than those on, say, a capacitor, but my Hakko desoldering gun has done such a great job in the past I figure it can tackle these little pins too. Of course, I've been wrong in the past about plenty of things...
 
Darn... I successfully installed the socket and the new chip but the measurements on the new chip are the same as the old one. I measured AC voltage on pins 7 (x) and 10 (x ground) on the big white connector that goes to the monitor. I'm getting 0.00 volts. Pins 8 (y) and 11 (y ground) fluctuate between .5 volts and 2.0 volts. I never see that voltage go into negative numbers.
What's the next step? I'm determined to get this baby up and running!
 
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