Y axis adjustment on Tempest

I posted the following on rec.games.video.arcade.collecting Sunday
morning. As of Tuesday night yet have not received any input. So, I am
posting this to the vector list to see if any of the experts have any
ideas on how to solve this problem. (posts edited from original query to
usenet)

As the title states I am having problems with the Y adjustment on my
tempest. I can not get the Y axis small enough to fit the screen.

Sequence of events:

1. Purchased machine one month ago with unstable video (Sine wave
running down the vectors)

2. Replaced all the electrolytic capacitors on the H.V. board. (Sine
wave problem resolved)

3. Went through the self test and made all adjustments ("Y Size" trim
pot was set to the smallest size to get proper screen fit, did not
change this as it was already set at the limit before I went through the
adjustment procedure)

4. Game played fine for several weeks with no problems. Then during a
game last night the Y size grew outside the limits of the CRT. Now I
don't have any adjustment left to bring it down the right size. (I can
make Y larger and the X size works fine)

5. I have checked the trim pot and the resistor in series with it and
both check out OK.

Any ideas on what I should check now?

Additional information

I pulled out the low voltage board this evening and found what I believe
to be a nonstandard modification to the circuit (don't really know since
this is the first machine I have owned). There is a daughter card which
consists of (2) 2N3904's, (4) 2N3906's and various diodes, resistors and
capacitors. This PCB is attached to the LV board with standoffs at the
following locations: R600, R700 (both sides), R606 and R700 (one side)
(these components had been removed from the LV board). In addition there
are standoffs in holes which are not labeled. This daughter P.C.B. looks
rather crude in comparison to the L.V. board but does carry ATARI
makings as follows:

ATARI c 81
MADE IN USA
038089-01
JPR II-2

I have a LV2000 but do not want to put it on until I get this problem
figured out.

Thanks in advance,

Scott Goings
Received on Tue Mar 3 15:34:03 1998