Technics 1210 internal regulation mods

[MartinT]

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.

[Wakefield Turntables]

you must do at least 12 hours of listening now and report back tomorrow morning with a 1000 essay on the changes you can hear.

[Pete]

you must do at least 12 hours of listening now and report back tomorrow morning with a 1000 essay on the changes you can hear.

Then reverse the mods going back to phase 2, just to double check the differences you think you heard with phase 3. Then redo phase 3, and check again

[Pete]

Martin,

Seriously, great job milking every drop from this motor circuit.....

BTW, what wire did you use for hooking up all the circuits?

Cheers,
Pete

[MartinT]

you must do at least 12 hours of listening now and report back tomorrow morning with a 1000 essay on the changes you can hear.

Actually, I only needed about one minute, the changes are that easy to hear. More later today when I get home.

[MartinT]

BTW, what wire did you use for hooking up all the circuits?

The wire is Paul Hynes Fine Silver, the same as used for my external feed from the SR5 (different gauge). If you order the regs from Paul, I strongly advise that you also order about 0.5m of this stuff plus sleeving as it makes everything consistent and it solders easily enough using Shark 5.5% silver solder.

[Marco]

Nice one, Martin. Look forward to finding out what you think!

Incidentally, now that you've done the regulator mods, can the whole shebang be connected to an SR7EHD (to take advantage of that massive tranny inside it, and its other benefits), or will it only work with your SR5?

If it's the former, then you've still got some fun to come, and goodness knows what that combination will do!!

Marco.

[MartinT]

There are two issues, Marco: different connector and different voltage. Both can be overcome by using an adapter and adjusting the voltage inside the SR7 to 27V - and remembering to adjust it back again before you connect it to your deck

[Marco]

So the ultimate is for you to get an SR7, and make the necessary adjustments?

If you rate the final regulator mods (which I'm sure you do), I think that will be the route I'll go: SR7 (suitably adjusted), plus all the 'gubbins' you've just installed inside your T/T.

That'll be a wee job for Anthony!

Marco.

[MartinT]

So the ultimate is for you to get an SR7, and make the necessary adjustments?

I'm just not sure if the SR7 will have any more impact through the TDR21 or if it will once more lower the noise floor and output impedance over the SR5. Perhaps Paul could comment?

That'll be a wee job for Anthony!

I'm sure he'll love it