Internal Regulator Upgrade (Phase 3)
Reminder: phase 2 involved splitting the motor control electronics from the motor drive and feeding each with a separate 21V supply from the Paul Hynes TDR-21 dual regulator, itself fed from an SR5-27. Phase 3 feeds a clean 5V to IC302 (4011 CMOS quad NAND gates performing clocking duties) and 9.4V to IC301 (AN6682 pitch control).
Assuming phase 2 is already done, preparation involves removing the main PCB and bearing and performing the following mods:
- remove D301 and R304 to isolate the 5V supply
- cut the track leading to pin 9 of IC301 to isolate the 9.4V supply
- solder two wires to D301 holes to provide 5V and return
- solder wire to pin 9 of IC301 for 9.4V (underside of board)
Now the main PCB and bearing can be carefully reassembled into the deck.
I mounted the two mini-regulators using plastic posts as shown in the photo (9.4V top-left, 5V top-right). Both are fed 21V from the motor control (top) regulator of the TDR-21, leaving the lower motor drive 21V for that duty alone. I took the 9.4V regulator return to the main star earth (bottom left post). However, Paul advised connecting the 5V regulator return to D301 anode because this needs to be a tight loop, which is why this reg is not star earthed. Finally, the 9.4V +ve and 5V twisted +ve/return wires were soldered to the regulator outputs.
It's a little fiddly keeping it all neat while leaving enough wire to first get the main PCB back in position and then the regulator PCBs snapped into place and I dressed the wires as best I could, taking care not to allow anything to foul the underside of the platter.
Final testing involved switching it all on and checking that both 21V rails, 9.4V and 5V were all present. Finally, I put the platter back on and tested both speeds with a strobe disc just to ensure that all was well with the drive electronics. Everything is running perfectly and I'm listening to it now.
http://farm9.staticflickr.com/8248/8...815d8717_b.jpg
