Hello from SF Bay Area .. just finished fixing WM-D6 that had spent 40 years with me

Hi all!
The contents here (esp. by Deb64) helped me greatly in the process of fixing my good old buddy WM-D6. About 4 years ago, I actually gave up after trying to fix the speed issue (and had bunch of torn cables from the board in the process, not to mention completely busted DC-DC converter). I put it in a time machine (a shoe box really) in the hope a future self would be able to get suddenly smarter and magically cure it out of pure magic.

Well the information here made me definitely a better wizard and I was able to fix WM-D6. Now I almost memorize WM-D6 service manual's circuit diagrams and wiring diagrams after spending full 36 hours on them.

In the process, I found a really good way to replace the problematic DC-DC (6v - 11v) step up converter without spending $40 on eBay or go through a lot of repair job on the old circuit. Will post it as a new thread in the tech forum and link it to the existing post on DC-DC converter repair that already helped me greatly. This is list of what I had to do:

* Follow on Deb64's post on CP602 repair by replacing one NPN transistor and one FET transistor
* Just remove mute module (CP301) -- new unit is coming from eBay
* Replace DC-DC converter with an easy to obtain MT3068 DC-DC converter (they are less than $1 per unit)

The MT3068 DC-DC converter is better than original design in many ways
* It holds output to set voltage (configurable by potentiometer) for wide range of input voltage
* High energy efficiency (>92%)
Benefits
* Battery almost drained -- but the walkman runs and sounds good!
* We can just wire adapter plug to widely available 5V USB output and the walkman runs!
* Low white noise (with proper capacitors added on)

Thank you for keeping this amazing forum and I hope to contribute more!

Best,
Chang