Chasing the Sony CX20084 speed chip for D6C walkman

My part

 

Man, if I had just seen this highly informative and important thread before using an AC adaptor with my mint low use WM-D6C that I bought some years back, it would still be working right. Yup, most likely fried the CX20084 when I plugged it in, as the D6C started running too fast shortly after, the speed control having no effect. I have a quick question: Who in North America and in Europe / UK, repairs these units and currently takes new customers? In fact, is there anyone who has gone a step further and managed to recreate the circuit using discrete components as an alternative solution (instead of the problematic CX20084) with some protection in place so that even plugging an AC adaptor with the wrong polarity would not harm the unit? I would like to explore the latter option. Again, fantastic info, thank you to all the contributors.

 

You might want to contact @Deb64. The only way to continue for now is to salvage the chip from another unit, here are a few if I remember correctly: WM-DC2, WM-DD2, WM-D3, WM-DD3, WM-DD30 [not WM-F200, WM-F202].
(I have a DD2 and DD3 that I can part with, although they look to good to me to rip apart just for the IC.)

 

@Emiel Thanks very much for the info. Yeah @Deb64 and also @Valentin are some of the top names that pop up often, talented people for sure.

 

@Emiel When sourcing some of these players for the IC, there's usually some cheaper ones described as for parts, not working or junk but how is the buyer to verify if these non-working units have a good IC or whether or not the IC has been already taken out, when buying from online sellers? Any advice?

 

The best way is to buy a DD unit that is in very bad cosmetic condition, but does still power on.
In the vast majority of cases DDs have been used on batteries, so the chance of a bad IC are minimal, despite not 0%.
There's no way to know for sure if the IC has not been taken out already, but chances are low.
If someone has already taken that IC out, they have probably kept the unit for taking other parts, not sell it online.

The F200/F202 have a different servo, so those can't be used as donors.
What will work as a donor unit are the following units: WM-DDII, WM-DDIII, WM-D3, WM-DD30, WM-DD1/WM-DD10/WM-DD11.
There are others from the DD series which this IC, but these are the ones to be considered as far as reasonable price goes.

 

Thank you @Valentin much appreciated.

 

Shoot, I made a mistake with the list. The CX20084 is next to the CX20123.
That is the servo IC in a lot of units (not DD), usually indicated by the traditional IC601.
Think of: Sony WM-10 and WM-30 Serial No. 77001 and later, WM-40, WM-100, WM-F200, etc.
I am working on making some of these overviews available on Walkman.land, progress is kind of slow.

 

The CX20123 was used in the WM-100 and WM-200 series as far as I know, while WM-10/20/30 series use a discrete servo circuit built around a NJM2901 comparator.
Then at the WM-500 series, when they switched to a normal DC motor instead of the 3-phase brushless they used before they also swtich to the generic AN6653 servo IC.

 

Take for example the WM-10II / WM-30 - up to serial number range 77000 it is the NJM2901B, above the CX20123.
Not sure what a Servo Circult is though