I am trying to repair and restore a Sony WM-D6 that I received not playing. I have been restoring vintage audio as a hobby for about 10 years but this is my first time repairing a Walkman or SMD board. I have a 10x visor and good soldering tip. Here is what has been done: 1. Replaced drive belt and exercised the FF/RW pivot and it's working good mechanically now. There were however speed and muting issues. 2. Removed CP602 and CP301 and soaked them in acetone for 24 hours and picked off the potting. 3. Replaced the NPN and FET on CP602 with 2SC1623 and 2SK209 from Digi-Key and reinstalled. Everything was working correctly so I ordered full rubber kit and pinch roller from fixyouraudio. 4. Removed CP601, CP302, CP303 to remove potting. After 24 hours I picked the potting off but had a lot more issues removing it. I guess I should have waited 48 hours! 5. On CP303 two of the transistors pulled off, and I replaced them with 2SC1623. Hopefully that's correct as I do get sound with setting on Normal, Chrome, and Metal. It plays super fast now though I am no longer getting any voltage on Pin 1 of CP601. Continuity tests good to the op amp Pin 7. All other voltages for CP601 match the schematic. What are the next steps in troubleshooting? I think buying a new CP601 would fix this, but would hate to do so and still have double speed. TIA!
Here are voltages on CP601 and CP602. CP602 voltages were all correct prior to removing and de-potting CP601. Something certainly happened to the module.. I am hoping it's something simple blocking the 4.5v on pin 1. CP601 1 0v 2 11.1v 3 0v 5 2.0v 6 0v 7 1v CP602 3 7mv 4 4.7v 5 4.0v 6 2v 7 0v 8 1.3v 10 4.1v 11 4.1v 12 2v 13 3.2v @Deb64 any ideas? Happy to purchase a new CP601 module if that will straighten things out.
You should be getting a sinewave out from Pin 1 of the CP601, with a frequency of 1.08kHz when running at the correct speed. Check the FG coil winding. If it is open circuit, or the wires from it are soldered in the wrong place, then the motor will run fast. Also, check that all the other wires are soldered into place correctly.
Thanks for taking the time to look at this, @Deb64 The black wire next to the FG coil connections had broken off. I reconnected it and still crazy fast. I don't see any other broken connections. There is no continuity across the FG coil and no sinewave off pin 1. Is the FG coil replaceable or repairable? Is it more likely the leads or the coil? Are there other issues with the voltages being so far off on CP602?
If the FG coil is open circuit, it will run fast so I would address that first. The FG coil should show a DC resistance of around 620 Ohms. Check the black wires on the FG coil; I have come across cases where they have been crushed by the casing when the walkman has been assembled incorrectly. Finally, you need to clean the flux and contamination from the areas around CP602 and CP601. Some fluxes are conductive and I have seen cases with two solder pads with flux on the land inbetween behaving like a capacitor. These motor control circuits are high impedance (as are the ones around the CX20084 on the D6C) and cleanliness really is important when working on them. Also check around there for any solder bridges or wire whiskers.
Thanks again Deb64. I think the FG Coil might be alright. I get 620 Ohms across it and can see a sinewave coming from it. I cleaned the boards with some IPA but every time I look at it wires break loose. I am definitely early in the learning curve with small electronics like this. I've tested for any continuity across adjacent pins on CP601 and CP602, as well as all the traces too and from, and everything looks OK to me. I have removed both chips a few times now, so pads are not in good shape.
Another thing to check is C607, which is a tantalum 0.15uF / 35V capacitor. I have had one or two of those which have failed and they cause fast motor running. I normally replace C607 whenever I repair a CP602 module since they can be problematic.
Forgot to mention I have replaced the 0.15uF tantalum. Does it matter if it's a bi-polar film or electrolytic as long as it fits? I've tried both with same results. I think I messed something up on CP601 depotting it. I ordered the replacement.
I have only ever used a tantalum so I don't know if using an electrolytic or film capacitor would affect it.
Replacement CP601 resolved my speed issue. In depotting the module, two of the SMD capacitors were chipped. I don't know if that was the issue, but glad it's resolved. Thanks so much @Deb64 for all your assistance and especially for making the replacement modules available.
Hi, I have same speed issue as I understand the reason is CX20084 I can't get original one for replace, only found on aliexpress, will try to replace when it came. I have a question all legs must be soldered to the board? In my case last one don't have connection.
The CX20084 is a 16 pin IC. The only pin which is not connected in a D6C is pin 6. There is a floating pad for pin 6 but it is not connected. If any other pins are not connected or broken then that would cause a speed issue. Apart from the broken pins, the chip may still be working. If you have a Dremel or similar grinding tool, it may be possible to grind away some of the plastic casing to expose the remaining parts of the missing legs. I tried this out on a faulty CX20084 some time ago as I thought I may have to deal with a similar problem to yours. In the end I didn't need to carry out such a repair but here is the chip which I experimented on. The plastic used on these chips is very hard so you will need to take your time and be careful with the grinding. Most importantly, make sure you keep a note of which is Pin 1 if you grind out the circular marker.
@Deb64 Thanks a lot for your advice, I soldered 8 pin and it works Manual speed control works to. But I can't understand how that pin could have disappeared from chip?
Thanks for the update @-LV- . I'm glad to hear that it has fixed the speed issues. Pin 8 is the 6V B+ connection so the chip would not have worked at all with the pin missing. Those pins can fracture easily if bent, so it must have been bent at some point during manufacture, fitting or a previous repair attempt.
@Deb64 is there a working method for protecting against over voltage and reverse polarity, maybe some schema or instructions? Since the CX20084 is very valuable these days I want to keep him as safe as possible
