The clock exact frequency isn't critical, seen units that were outside the specified interval and still worked fine. It has to be off by a lot to actually cause issues. In regard to the motor, note it can be tested outside of the walkman. Refer to page 8 of the pdf service manual (pages 11, 12 of the actual manual). To test you need to connect pin 3 to B+ and pin 4 to B+/GND (clockwise/counterclockwise rotation) through a 4k7 (or higher) resistor. After you get the motor running, check that when motor is stopped by hand, the current draw is ~250mA. If not, perform the adjustment at page 8. Also motor should be able to start again on its own after it's released, even at 1.7V B+. As a sidenote, these disc motors don't have a lot of torque, so the finger feel test is only relevant if you know how a good one should feel. Regarding the unit stopping, if "stop" means the mechanism unlatches it's related to lack of reel rotation signal. If the sensor is faulty you can take it from that JX505 donor you used before. If however just the motor stops and mechanism remains engaged, it's a logic control problem.
Leaving an update here, i have finally found the problem and it was my fault here. Basically, when i was transferring the sensor over to new pcb i started soldering it from the back of pcb. The solder didn't make connection because i didn't know that solder have to run through both sides of the pcb through hole. I can now go through the process of motor torque adjustment, tape speed , and adjust dolby pots. Thanks for giving steps and helpful advice. Almost forgot to mention, i already have the belt on order from fixyouraudio(thanks for the belt specification).
Normally the solder shouldn't need to run through to the other side to make a connection, assuming the hole is copper plated. In your case it's possible the PCB either had a manufacturing defect or a design error.
I think it's possibly a design error because i did find other problems while transferring over to new pcb. I found that 2 of the soldering pads were missing and i had to scrape off solder mask on copper trace underneath to put in the smd caps. I have question regarding azimuth calibration process. Do i need a higher frequency calibration cassette to adjust azimuth? I do have 3000hz calibration cassette i got awhile back. Also, i have a basic handheld oscilloscope(zoyi 703s) and it has 2 channels.
In theory you could use the 3kHz, but this tape has 2 problems: frequency is a bit low and also it's not a full-track. In practice it's probably not any better than simply adjusting it by ear using a known-good or pre-recorded tape. Really depends how much you think you are going to use such tape. If you would need in other units, it's worth buying a HPR azimuth tape.
I'll get HPR azimuth calibration cassette. I'm thinking of getting the 10kHz calibration cassette and 400Hz Dolby calibration cassette. I can see that HPR provides various range of calibration cassettes and i don't really know much about it. I think i only really need 10kHz and a 400Hz Dolby calibration cassette just to start off this hobby of mine. Also, I decided to borrow another belt from jx505 just to test the machine and do a rough calibration on it. I did tape speed calibration, azimuth calibration on a 3kHz tape, and i did adjust the Dolby potentiometers with 10uF 16v caps(they do need 400Hz test tape right?). Next, I decided to do a touch test on pcb while machine is playing. I noticed that when i touch resistors and smd caps on the pre-main section of the machine it will start doing distorting sound on the right channel(sounds like maracas) and sometimes when i touch it the sound on right channel is gone. Without doing touch test the sounds are working fine. Furthermore, I checked the bass boost functions and it seems that higher bass boost levels just gives distortion when there's a huge bass drop. The low bass boost at level 1 is good but higher bass boost and higher level will cause distortion at the peak of bass drop. I don't know if this is related to the pre-main distortion or not but i don't think it supposed to do that. Please let me know if these are normal machine behavior or not. Thank you.
Yes, for the most part the 10kHz azimuth and 400Hz Dolby level are enough, given you already have the 3kHz speed/W&F one. For the Dolby level, get the 218nWb/m one, as that's the correct ANSI standard, although both tapes are very close to each other in practice. Regarding the levels, you don't need the series capacitor if measuring with digital multimeter. For the tape, the standard is important, ANSI only exists as 400Hz. But the tape is good for units that have the procedure for DIN (330Hz), with the level conversions (200nWb/m ANSI is 2.7dB higher than 160nWb/m DIN). On this unit you need 100mV RMS with the ANSI tape. The distorsion/static when touching the preamp section is normal. Regarding the DSL, what headphones are you using ? And does it distort at all volume levels, including lower volume settings ? It is normal to distort at high volume levels and DSL on max.
Thanks a lot for the detailed explanation, it helped me understand the ANSI/DIN differences and the correct calibration levels much better. I’m using Moondrop chu 2 and it definitely seems like it can’t handle the DSL bass boost very well at higher volume. I also have a Moondrop Blessing 3 but unfortunately the right side is dead at the moment. Thanks again for the help, I really appreciate it.
