I'd assume setting the mechanical alignment of the pickup for best
performance would be the best (and only) option with the test gear you
probably have at hand. If it was a 3 beam pickup (which I am quite
sure of) and RF was derived from the center photodetectors A-D only,
the scope on the RF Packet would not give you any clue if the outer
photodetectors E and F have get clean signal -and AFAIK they are the
ones responsible for tracking. And remember that Pickup was toyed
with, so you do not know if it can be aligned properly at all.
The problem of random skipping may also be caused by a worn out motor
bearing even though you say the disc would not appear to have
excessive run out - so scope the tracking and focus signal for high
signals repeating along with the turning of the disc and try to
replace the motor on trial and error basis if possible. And since it
is a portable do also check the clamp on the disc platter. IIRC this
is the one with the button on top to be pressed to release and popup
the disk- one of the springy clamps on the holder may have been bent
or the disc slips.
OTOH given the state the player was in I'd say you are pretty lucky
you got it working at all.

-Melissa

Rainer F. Daltrop wrote:

If I adjust the lens tilt for best performance I have a sharp
eyepattern of almost stable height at ~0.8Vpp and the player skips
occasionally. But if I adjust the lens tilt to provides the strongest
eyepattern (~1Vpp) the scope shows noise in the pattern and a general
change of RF packet height along with the revolution of the disc
(though the disc itself does not wobble) - the player may even fail to
readthe TOC or jump to the first track.