Shaky Star Wars

Waah!

I've got an star Wars w/ amplifone that is driving me *mad*.

The boardset is tested okay.
The problem was with the amplifone monitor, the Y amplifier had two toasted
MPSU07 and MPS57 drivers (tested okay, but caused -12V offset at the
output).
Replacing them corrected the problem and for a day the pricture was
brilliant and stable.

Now suddenly there is a ripple in *both* the X and Youtput, causing the
image to 'wobble' on the outsides.

I can't explain it or find the cause:

- Replaced filter caps on amplifone defl. board
- Replaced the 2n2792 and 3716 pair
- The ripple is present at the bases of the final drive stages of the amp
board.
- There is no ripple on the input of the differential amplifier consisting
of TR1, TR1 and TR3 (2N2904's)

Since the problem arises on both X and Y outputs, Tere should be a common
cause, but that just leaves the rectifier, the filter caps and the
transformer in the power supply. I tested for ground connection and also
tried connecting a direct ground wire from the game board to the amplifone.
There are no dry joints on the defl. board.

Anyone has any good ideas on what can cause this problem?

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Received on Thu Feb 5 16:30:36 2004