My unit start to vibrate in play mode with speed tune off. With speed tune on mode the motor is dead quet and can be speed adjusted . I replace IC601,C601,C602,C315. No success dow It is very strange the motor is fed with the right voltage but it buzzing, knocking sound and vibration. Now it play slowly in speed mode off maybe is problem with quartz crystals lock. Can someone help?
Is it late serial number? I had this issue with a late serial 4th revision, had to replace a mylar cap on the quartz lock circuit.
Hello Sanchos. I have just looked at your video. I haven't come across this problem yet so I'm not sure of the cause. Do you have access to an oscilloscope and a multimeter? Can you power the walkman from a bench power supply so that you can monitor and limit the current drawn? The "Auto Off" circuit around Q701, Q702 and the photo sensor causes the servo IC to cut the power to the motor when there is no motion detected on the supply side spool, such as when the walkman is in FF or REW mode and has reached the end of the tape. What are you getting on pin 7 of IC601? If the supply spool is rotating then it should be a square wave. If there is not a square wave then you need to check the "auto off" circuit. I think a failure of the crystal itself is unlikey. It's rare for a crystal to fail. Check pins 1, 2 and 3 on IC701. You should get a 34.7kHz square wave. If there is no square wave then I would change the capacitors C703, C704 and C705 before looking for a replacement crystal. I have never had a MSM58141RS IC (IC701) fail yet but if it is this then your chances of finding a replacement are extrememly slim. However, I did get hold of some surface mount MSM58141MS-KR3 ICs from a supplier in China. I fitted one onto a SMD to DIP 8 converter and fitted it into a WM-D6. It works.
Just a thought. Before you check the above, is the pinch roller pressing on the tape and capstan as it should? One of your videos shows the capstan flywheel, which looks as if it's turning at the correct speed. The tape isn't moving at the right speed. Maybe the slow forward movement of the tape is due to the tension on the take up spool only, with the capstan not controlling the tape speed, due to lack of pinch roller pressure.
The problem disappeared after I sprayed the board with isopropyl alcohol. I have no explanation, but it has been working fine now for two days. I'm surprised, something has made quartz lock the speed.
