Dear friends, i have a problem in the radial correction circuit. The player reads CDs TOC with all but most when it gets to tracks 8 9 10 .. the mechanics start to make noise and the audio distorts. Checking the measurement points as per the service manual, I realized that I have wrong measurements in two points. Pin 1 of Q214 (LM324) in Stop measure + 500mv. instead of -7.1V and at Pin 14 of Q215 (LM324) I measure -3.05V. instead of -11.4V. In Play the measurements in these points are like the manual even if not stable. doing various tests I realized that by disconnecting the radial error connector on the CDM0 board, the measurements listed above return to being perfect. The mysterious thing is that I first replaced the servo board then also the CDM0 drawer but the problem remains the same. If anyone can give me any suggestions you will be grateful, I am really heartbroken.
Thanks!
I enclose an image of the circuit.
2021-11-08 08_45_25-1.png - Google Drive
Thanks!
I enclose an image of the circuit.
2021-11-08 08_45_25-1.png - Google Drive
Attachments
Have you replaced the 33uF caps on the servo board (particularly the one related to the laser power control circuit) that are a known problem?
Yes all 33uF. they have all been replaced in the servo board, the strange thing is that even replacing with another servo board the measurements are always out of order. If I disconnect the radial error connector, the measurements are perfect 🙁
As you say it plays OK up to later tracks on the disc then the thing to do is to look at the RF on a scope and see what is occurring.
These are old players now and caps are the usual cause of problems. You must also check all rails are correct and clean.
Other possibilities are mechanical issues with the swing arm sticking or the angle changing as it track outwards on the disc.
These are old players now and caps are the usual cause of problems. You must also check all rails are correct and clean.
Other possibilities are mechanical issues with the swing arm sticking or the angle changing as it track outwards on the disc.