Sony DD portables genealogy

No, I was reffering to the 3 versions of the heads: pointy, 35711 and 35712 permalloy. Will edit the wording for more clarity.

 

Does anyone know the WM-D6C serial numbers affected by the Dolby circuit changes specified in Supplement 1 (January 1985)?

 

Good findings, but are they conclusive to make updates to the table? Let me know, happy to improve the overview!

 

Here's what I have gathered so far on the Sony Walkman D6C history (updated 8/30/2024). This is from postings on stereo2go, tapeheads, and for sale listings on eBay:

• February 1984: Sony Walkman WM-D6C released. Amorphous "pointy" PA259-3602A head marked "Japan". Brown/green phenolic PC boards 1-611-494-11 with through-hole components.
  
• January 1985: Supplement 1 notes Dolby chip change from CX20068 to CX 20218, as well as surrounding component value changes. PCB now -12. Serial #s affected are unknown
  
• Change from pointy head to rounded amorphous head 35711 between serial # 71236 and # 72264. Date unknown
  
• 1988: Change to Dolby sticker color from white (silver) to black between serial # 114373 and # 117947
  
• March 1994: Supplement 2 (serial # 267201) notes change to green glass epoxy PCB 1-651-545-12 with SMD components.
  
• April 1996: Service Bulletin 395 issued. The motor was changed from X-3305-830-1 to X-3370-805-1.
  
• April 1999: Supplement 3 shows two resistor values were changed in the French model.
  
• June 2001: Supplement 4 shows main PCB changed to 1-651-545-14; motor drive servo circuit redesigned with servo IC now CX069A. Service manual was issued as Rev. 1.1.
  
• Change to permalloy head 35712 in serial #s ~50xxxx and above. Marking "amorphous head" on the case is no longer present.
  
• 2002: WM-D6C production discontinued

Please update the genealogy table. If anyone has additional information, PLEASE POST IT.