Hi Ben, Do you have an oscilloscope, it's the only way to adjust/check any player. You have to be able to "see" the signal coming off the disc to correctly set up. You say someone has twiddled the pot's, that could be a problem and I think you need access to the service manual. Depending on the machine there may be adjustments for focus and tracking gain, EF balance and PLL lock. As a generalisation you can try this. If it will play at all, if you turn the focus gain up you may hear "white noise" coming from the optical pickup itself, adjust up to the point that the noise is apparant and then back off slightly. Tracking gain set initially to around mid point. EF balance is very critical, you certainly need scope for this. Try moving slightly each way and see if playability improves. PLL or phase locked loop again very critical, you need the set up procedure to adjust correctly and a frequency counter. You can set it to the midway between the points at which the player "loses it" assuming it is a pot for this adjustment (sometimes a coil, if it is don't touch). If you have a 'scope you may be suprised to see that the RF signal or eye patern coming off the disc always looks the same, it does not matter what the content of the disc is, the only exception is the "gap" between tracks tracks. Good luck
Not familiar with that particular unit. First things first, A clean lens, and put scope on the RF signal. This tells all. Does the manual give an amplitude for this signal, usually about 1.2 volts PEAK TO PEAK on scope. Is the "diamond" shape clear when you expand the timebase on the scope.
Is there a set up procedure in the manual for EF balance, this is critical adjustment. Needing a signal generator to set up the spindle motor implies a hall effect type motor. Dont think this is problem really, once playing the motor should not loose lock.
The RF signal or eye pattern is the one to measure. It is the signal straight off the disc from the RF amplifier before it is applied to any of the digital processing stages. Unless a new optical unit has been fitted or it's had the pots turned it should not really need adjustment. If you do measure it be sure to use a correct ground for your 'scope. If you just use the case etc or "any" ground point this in itself can make the diamond shape look fuzzy. You really need a manual before you attempt adjustment. Is there any specific problem with the unit ?
Unit plays discs and read TOC. One problem is belt for cd draw and it seems a bit tricky to exchange since this unit has very interesting mechanical solution for drawer mechanisam. I would like to check other parameters, but I don't want to do it until I found service manual for it with proper alignment procedure. And yes, for PLL it uses coil!
Player works fine, but since it is about 25 years old, perhaps some adjustments should be done, or, at least, detail checking is recomended. I repair electronics for more than 20 years and 'gained my degree' on VCR's and hi-fi equipment.
Right now, I am looking for service manual with alignment checks/procedures.
I saw your discussion with Sony DAT problem and I posted my opinion there