RE: Tempest Troubles - Please Help

Sounds like the voltage regulator is bad, or it's not getting the correct
input voltage (this is where the DAC gets it's power from). Find the 7815 on
your board and make sure it's getting +22 on the input leg. If it is, then
replace it. Also check your -15 on the 7915 while your at it.

-jeff

-----Original Message-----
From: Jon Raiford [mailto:raiford@mindspring.com]
Sent: Wednesday, March 31, 1999 6:04 AM
To: vectorlist@mcfeeley.cc.utexas.edu
Subject: Tempest Troubles - Please Help

I finally tracked down the proper power supply for my tempest,
but the game still plays blind. I went to the Diagnosing Tempest
page (http://www.kfu.com/~nsayer/games/tempest.html) and walked
through the hyperlinks and this is what I came up with:

Start
 * No video, LED on monitor deflection PCB on, start button LEDs blink, game
basically plays "blind"

Spot Killer
The spot killer has activated indicating either X or Y deflection is not
occuring properly. Take a scope or a voltmeter and look for +/- 6 volt
swings
on the X and Y out loops on the main board.

* No, one or both are stuck (the actual reading was .3 on both, I think)

VSM Analog faults
One or both of the deflection outputs is stuck at this point. I will presume
it is the Y deflection that's not working. You will have to adapt a bit if X
is the problem.

Turn the brightness up on the monitor SLIGHTLY until you over-ride the spot
killer. Don't leave it like this very long! It is very bad for the tube to
not be deflecting the beam a lot. You should now see the screen "crunched"
into a flat line. Wiggle the Y centering pot. Does the line move up and
down?

* No (Neither the X nor Y pots do anything.. just the dot in the center)

Check deflection output amp
It appears that the final output amp of the deflection section (D/E13) is
bad. Also check C13, the analog multiplier.

I replaced D/E13 and C13 for the Y axis and the same chips for the X axis,
but there was no change.

While I was poking around, I noticed that the +15v test point was only
reading 3 volts. Is the 15v used "for +/- 6 volt swings on the X and Y
out loops on the main board"? Where should I look at this point? All
other voltages are ok, and when I put my (what appears to be dead
although was supposedly working when I bought it) Major Havoc board in,
it does have the 15v. I guess what I'm saying is that the power supply
and ar2 seem to be ok. Any thoughts?

Jon
Received on Wed Mar 31 10:29:46 1999