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.
Hello again, I have installed the new belt and adjusted tape speed, i noticed that the tape speed on rew side is at 3070Hz and fwd side is at 3000Hz. I tried etching both capstans and noticed that it doesn't make any significant changes(i did this twice and it just add more wow and flutter). I think this is possibly a pinch roller problem(maybe), i think my pinch roller is slightly more worn on one side than the other. Is there any place i could get new pinch rollers? Also could this also be from incorrect use of capstan bearing lubrication? I did used molykote em-30l on the brass stand off that the capstan ride on because it was making noise. I cleaned capstans with ipa after applying the grease just in case.
The speed difference isn't caused by polished capstans unless the wear is extreme and tape is actually slipping, but in that case you will also have very high W&F combined with low speed. 70Hz speed difference is indeed high, though 20-30Hz can be normal. Rollers can be the culprit, but same as the capstan you will also have increased W&F combined with low speed, not just one. New rollers can be found on goofish.com, haven't seen them anywhere else. However wouldn't jump on the rollers unless they're visibly different even after a deep clean. Capstan bearings should be lubricated with watch oil (not grease) if you haven't done so already. Pay attention one of them has a very thin washer below the main cut one. Also check the etching hasn't been done on the part that goes inside the bushing, that will create excessive friction. This is what could have made the W&F worse after the second pass. After etching also be sure to clean everything very well (capstans, rollers) before using any tape.
Thanks for the reply, I have removed both capstans, cleaned out the grease and added watch oil to bearings now. I decided to tape up the top part of capstans and apply metal polish on the lower part of the shaft that sits inside the bushing. I then cleaned it off with IPA and reinstall it back into mechanism. I already checked that both capstans has its thin washers underneath. There is 3 washers per capstan one sit underneath and ride on bearing, then a clear washer that sit on the locking groove, and the black plastic washer that locks on the groove itself. I managed to get 3000Hz on fwd side and 3047Hz on rew side. I am still trying to figure out the cause of this. I might actually swap capstans or pinch rollers with jx505 soon. Also, if that makes a difference then i will actually try to find replacement pinch rollers. I made sure to clean everything with IPA after installing back. I think this part is going to take awhile to dial in. I noticed that jx505 capstan is abit different, it has a spring underneath it and the brass piece on it look abit more thin. Will it work as a direct swap?
You can also swap the rollers between FWD and REV in order to see if this is the problem. What W&F figures are you obtaining ? JX505 capstan/flywheel assy may fit, but can't confirm that. You need to try it yourself. The small spring is similar to the 0ZM-4 mechanism, think the purpose of that may be to add a bit of extra friction on one of the capstans to eliminate resonance. When I first saw this spring I thought it was for reducing thrust play, but in this case both capstans should have had it (which isn't the case). One solution to fix the speed difference problem is to sand the capstan that has the higher speed to a lower diameter (while rotating). However this should only be used as a last resort as the diameters themselves are likely not the root cause. EDIT: Also if you haven't done the motor torque adjustment do that also. If torque is on the low side, that can also create a FWD/REV speed differencce as the resistance won't be identical on both directions.
Actually, i only tested one direction of the motor torque because at the time i figured that the current is exactly at 250mA when stopped by hand and i decided not to look at it. I decided to use WFGUI to measure tape speed and check for wow and flutter values.I noticed that my previous way of measuring tape speed was off by at least 10Hz. The only explanation i can think of is that the grease on the capstan bearings caused speed difference and then i proceeded to unnecessarily etched capstans which causes more wow and flutter. Now i will need to somehow fix this issue because i can see that rev side isn't consistent. The tape speed on REV side is close to the acceptable range and is hovering around 3033Hz-3037Hz. I have attached photos of the test and i noticed that fwd side is more stable than rev side. During the flutter test i can see that rev side isn't consistent. I can see in the graph that sometimes there is a spike on it. The machine also struggle to pull through tape leader and i have to fast forward through it and then press play. this happens on both side of playback. EDIT: just checked that jx505 capstans won't work on this machine because the countersink on the brass flywheel isn't wide enough to sit on the bearing. Also, i might actually swap over the pinch rollers from jx505 that i have here. seems like the pinch rollers looks newer and might have been replaced by previous owner.
Hello, I decided to replace both pinch rollers with the ones from my JX505 donor unit. As the machine currently sits, I am measuring around a 40Hz speed difference between forward and reverse playback. Looking back, I think I should not have started etching the capstans before investigating other causes first. The original issue may actually have been related to using the wrong lubricant on the capstan bearings, which likely increased friction and contributed to the speed difference. At this point, I suspect the capstans may have been etched unevenly. After switching to watch oil and polishing only the bearing-contact portion of the capstan shafts, the situation improved somewhat, but there is still a remaining speed mismatch and noticeable wow/flutter. Is it realistically possible to recover the capstans by carefully polishing/equalizing them further, in order to reduce wow/flutter and make both directions behave more evenly? Or would replacement capstans be the better approach at this stage? Thank you.
