This thread covers the complete restoration process of the SONY TC-K411 deck including both the mechanical side and calibration of the electronics (which is needed, despite the external cal feature). Parts you will need: 1. New belts: https://webspareparts.com/products/sony-tc-k411-belt-kit-for-cassette-deck 2. New pinch roller (uses the standard 13x8x2mm one): https://fixyouraudio.com/product/pinch-roller-13x8x2mm/ 3. New gear for the secondary motor: https://fixyouraudio.com/product/sony-tc-k411-motor-gear/ Oil used should be watch oil. The belt kit from webspareparts is the one I used and was very happy with it: wow&flutter obtained was 0.062% WRMS (lower than the 0.07% WRMS spec). MECHANICAL SIDE: 1. Start by removing the top cover held on by 4 screws; 2. Remove all the cables going from the front panel to the PCB (marked in red on picture); 3. Remove the screws holding the front panel on; 4. Remove the front panel; 5. Remove the deck itself from the front panel (it's held by 4 screws + the cassette door cover); 6. Remove the top PCB from the deck; 7. Remove the motors assy from the deck; 8. Clean all the old belts residue and the pulleys; 9. Lubricate the capstan bearing (pay attention there is a plastic washer on the opposite side); 10. Lubricate the motors top bushings; 11. Take the PCB with switches out, remove the plastic covers on leaf switches and clean them with contact cleaner and cotton swab; 12. Replace the gear on the secondary motor (should be replaced even if not fully broken); 13. Put the new belts as indicated on pictures; 14. Reassembly the motors assy and slip the new belts back onto their respective pulleys; 15. Replace the pinch roller as indicated in pictures; 16. Clean any oil residue on the capstan remained from lubricating the capstan bearing; 17. Reassembly the deck onto the front panel; 18. Remove the potentiometeres board from the front panel and clean all the pots with contact cleaner; rotate them 20-30 times full rotation to make sure any oxidation is removed; 19. Reassembly the front panel back onto the deck and re-connect all the wires;
On the electronics side, it important to ajust the following: 1. Playback level (this is usually the most off and very uneven between channels); 2. Record level 3. Bias Record level and bias should be ajusted because the external adjustment is one for both channels, so if there is any channel imbalance, you cannot compensate for that using the external pots. What tape you use for this adjustment is oviously not critical (as you will adjust futher using external pots), so use a tape of your own choosing, but prefferably one that has not been recorded before for best results. ELECTRONICS SIDE (note adjustments should be made in the order presented): 1. Playback level SONY specifies the playback level on the LINE OUT (loaded with 47k) should be 320mV RMS with P-4-L300 tape (160nWb/m DIN). This translates into a 421mV RMS when using a Dolby level tape (200nWb/m ANSI), which is what I recommend using. Note it is very important to load the LINE OUT with 47k, otherwise your levels will be incorrect. TRIMPOTS: RV121 (left channel) and RV221 (right channel). 2. Record level With both external calibration pots put on center point (where they click), feed the device with a 315/330Hz test signal. Adjust it to -10dB on the VU-meter. Monitor the line out using a TrueRMS multimeter or digital oscilloscope (remember to load the output with 47k). Note the voltage when unit is set to SOURCE. Adjsut the internal trimpots so the TAPE has the same level as the source on both channels. TRIMPOTS: RV101 (left channel) and RV201 (right channel) 3. Bias With both external calibration pots put on center point, feed the device with a 10kHz test singal. Adjust it to -10dB on the VU-meter. Monitor the line out using a TrueRMS multimeter or digital oscilloscope (remember to load the output with 47k). Note the voltage when unit is set to SOURCE. Adjust the internal trimpots so the TAPE has the same level as the source on both channels. TRIMPOTS: RV103 (left-channel) and RV203 (right channel). The tape speed should also be check and adjusted if necessary with the trimpot located on the deck itself (not the trimpot on the motor). The one I repaired was pretty close at 2995Hz and I adjusted it to 3000Hz, despite it would have been perfectly fine without adjustment.
Valentin, very nice tutorial: I'm amazed you find the time between many Walkman tutorials and this cassette deck tutorial, excellent work! And I truly appreciate the technical guidance: I found this tutorial while looking for information on a problem I'm having with my Sony TC-K71:
Hallo Valentin. Is it possible to adjust the speed without any precise measure instrument? If yes, where are the speed adjustment tripods?
It's always possible to adjust by ear, but it's something I don't recommend doing as it's not an accurate method of adjusting it. Adjustment trimpot is on the back of the motor.
