This service manual of the old video cassette recorder VT-LC50EM is very good readable even the tiniest numbers (i.e. IC-pins). The circuits are very clear. Many details of the schematic are very good described but in GERMAN language. Many schematic details - but complete at all. Common background information of several details are enclosed and physical knowledge of the TFT liquid crystal display for example. The manual lacks PCB drawings. If you understand german I would recommend this manual for you.
Text excerpt from page 27 (click to view)
CD SECTION CD PICK-UP MAINTENANCE
About pick-up (Optical lens) Cleaning Clean a lens with swab of the cotton which moistened it with alcohol, cleaning paper or cleaning disc appointed. Specified cleaning disc : LC-1 (Part code : 645 026 1961 ..... manufactured by SANYO.) Show a clean procedure in the following in reference by swab of cotton. 1. Cotton swab is wrapped with Cleaning paper. 2. Add the isopropyl alcohol. 3. Gently move the tip of cotton swab just like a draw a whirlpool from inside to outside on the surface of lens.
CD PLAYER ADJUSTMENTS
1. ADJUSTMENTS
(1) Confirm the tracking balance 1. Turn on the POWER switch. 2. Connect an Oscilloscope to TP2 (TE) and TP4 (VC). 3. Set the test disc. 4. Press "PLAY" button to turn into the "PLAY" mode. 5. Keep holding "SKIP" button down so as to be "SERCH" mode, then confirm that the oscilloscope waveform is symmetrical on the top and bottom in relation to 0V (VC).
200mV/div. 5ms/div. (2) Checking the "eye" pattern 1. Switch "ON" the POWER. 2. Connect an oscilloscope to TP1 (RF) and TP4 (VC). 3. Load the test disc. 4. Press the PLAY button. 5. Check to be sure that the "eye" pattern is at the center of waveform and that the diamond shape is clearly defined. 6. Press the STOP button. 7. Turn off the POWER switch.
TP1 (RF) TP4 (VC)
a
