Welcome to Beoworld !
It could be something else but the vast majority of read faults in these decks are
caused by bad capacitors on the laser servo board.
The electrolytic caps needs to be replaced and at least one of them needs
to be a specific brand and type, namely the blue Philips axial C2103 as you will also
notice if you do a forum search.
Capacitor kits are available (from me) for most of the different servo boards used.
Check the number in the corner on the solder side of the board, the last 5 digits
will tell the type. Something like 34114, 35013 or similar.
Also worth checking for cracked solder joints, especially around
the voltage regulators.
Replace the capacitors and leave the trimmers (variable resistors/adjustments) alone.
An adjustment hardly ever goes astray.
You can check (and eventually adjust) the laser current ONLY if you have
correct instrumentation and the test CD(s) needed to do so, and even then it should be
done with the utmost care.
The chance of destroying the laser is too high if using trial and error.
It only takes a few seconds with a too high laser current to count laser life in minutes
rather than years or to turn the laser dark forever.
I would strongly suggest you leave the adjustments well alone and just replace the capacitors.
If this does not fix the problem, and I'm sure it will, it's much more likely to be a defective laser than a bad
trimmer or adjustment but you can check it by then. You cannot trust anything as long as the old
capacitors are still playing a role. The adjustments are set to match the laser block. Increasing
the laser current will not compensate for bad capacitors and the focus compensates for tolerances and
physical distances within the laser diode/block/mechanics construction so no need to ever adjust any of that.
Martin