Hi everyone! Up until now, my journey of restoring my old Sony DD Walkmans have been more or less straightforward. However, I recently bought a WM-DD33 with many issues, feeling confident that I would be able to solve them. I was wrong. It has at least two issues that I need some advices in order to fix them. 1) it has a spot of rust on the chassis, and I would like to know what is the best way of treating it and the right paint to use. 2) it has speed stability issues. When using a 3kHz calibration tape, almost all the times I press play, it locks to +-2800Hz. On the other times, it locks to 300.5Hz. When this is the case, it has two behaviors: on some occasions the W&F is good (0.05%) and other times not so much (0.2%). I thought the issue was on the quartz lock, so I unbridged the PLL to remove it. But now, even adjusting the RV601 I can only get +-1kHz!! I also checked the capacitors and they seem ok. Any advices or suggestions are more than welcome. thank you! Best Regards, Jose
Hi Everyone, I have taken some measurements with batteries - IKEA LADDA 2450 - without cassette and PLL unbridged, and I read the following voltages on IC601 pins: 1 - 1,163 2 - 1,171 3 - 1,180 4 - 1,460 5 - 1,522 6 - 1,492 7 - 2,606 8 - 2,603 9 - 1,06 to 1,13 10 - 0,19 to 0,21 11 - 0,500 12 - 0,155 13 - 0,170 14 - 0,166 15 - 1,960 16 - 0.00 (GND) There are many values that are way off. I will get my oscilloscope out of storage and chip the waveforms at pin 4. Best Regards, Jose.
Some of the values are indeed off. But the fact PLL is disconnected and battery voltage is not 3V will influence this circuit. I suggest changing the strategy because we're really not interested in all the voltages but rather if some key areas of the circuit are working: 1. The voltage reference. This is present at 1.52V and it's close enough to the specified 1.6V to believe it's fine. 2. The sawtooth waveform at pin 4. You should have this waveform there even with the PLL disconnected. When these ICs don't work (usually due to walkman being powered with reversed polarity), the reference voltage is not present. However, before suspecting anything electronic I would want to make sure there's no mechanical problem. Would check the following: 1. Is the motor rotating freely ? Remove the motor and rotate by hand in both directions. 2. What current does the motor draw with no load ? Power the motor with a bench power supply or battery (1.5V) and measure the current consumption. Should be 10-20mA. 3. Is everything clean mechanically ? Clean the rubber ring with IPA, motor spindle, capstan and pinch roller just to be sure.
