Hi ! Today I want to share with you the restoration of a pretty rare walkman, the Pioneer PK-R7AW. I have bought this one on ebay a couple of months ago and only recently I had all the necessary parts to repair it. The unit is in near mint condition cosmetically, the problems that it had were the following: - motor does not run at all - belt melted - one channel of the headphone amp not working After opening the walkman, I tested the motor on a lab power supply, confirmed that it was ok. After that, I instantly suspected that the device has been powered with reverse polarity. This was confirmed by the capacitor placed in parallel with the DC input being blown (I did replace that one). That led me to believe that both the motor governor LA5524 and headphone amplifier TA7688F were bad and in need of replacement. I first ordered the motor governor and tried a belt from Marian's set of 13 belts (thin type). The motor did work after replacing the governor, but the belt was slipping when engaging the auto-reverse mechanism. I decided to order a belt specifically for this unit, which was 1mm thick (the belt is 55mm x 1mm). At this point in time I also lubricated the capstan bearings. After this, I tried the unit once again, and it worked on one channel, but on the other I could hear loud motor hum and the sound was very crackly and low volume, typical of a transistor failure (in this case a transistor inside the IC). At this point I was 100% confident that the heaphone amp was damaged, so decided to order a new one. After replacing it, everything works fine and it sounds great. The final step was to adjust the motor speed and the Dolby level. The level on this unit should be 100mV RMS (400Hz @ 200nWb/m). Mine measured 90mV on left channel and 80mV on the other (the service manual specifies a +/- 20mV tolerance, so theoretically it was within spec, but I adjusted it to 100mV exactly and it sounds perfect with Dolby ON).
