Technics 1210 internal regulation mods

[MartinT]

It goes against the design principle of having the regulators as close to the active circuitry as possible, Chris. This keeps voltage drop to a minimum and 'stiffens' the voltage rails. The real villain of the piece, the transformer, is long gone and inside the SR5, where it belongs.

[The Grand Wazoo]

Ah, OK - fair enough then!

[sq225917]

You could use a reg with Kelvin sense then it wouldn't matter where they were as wire is compensated for in the reg itself.

[Reid Malenfant]

You could use a reg with Kelvin sense then it wouldn't matter where they were as wire is compensated for in the reg itself.

Indeed, this is exactly what was employed on various SMPS that I used to mess about with in my previous job



Looking forwards to seeing how it all pans out Martin

[Wakefield Turntables]

Here are my Paul Hynes internal regulator upgrades on an already heavily modified SL-1210. This phase 1 involved simply mounting the TDR-21 (twin PR3) regulator board inside the deck, setting one reg to exactly 21V and driving the entire PCB from the one supply. My external SR5-21 became an SR5-27 by adjusting it for 27V output. I went for phase 1 to start with because I wanted to evaluate just a single internal regulator compared with phase 2 which involves a further three regulators (2 x 9.4V & 5V), several components to remove and PCB tracks to cut.

Opening up the deck and preparing to mount the TDR-21 into the transformer well at top left. Beware those die cast posts! I used a self-tapper just a little too large and broke it inside the post I then attempted to drill it out and broke the drill bit in there Several hours later and I had the situation under control. I also spent some time removing the base and replacing the expired bulb inside the pop-up post with a white LED. This was more fiddly than I expected.



Showing the TDR-21 wired in and running, generating 21V from the incoming 27V from the already adjusted SR5. Left meter showing SR5-27 output and right meter showing TDR21 motor drive (nearest reg) output. I've also set the other reg to 21V ready for phase 2. There is some settling time with all the Paul Hynes regs so the meters are showing a little drift, which I have now brought back in.



Phase 1 fully wired and tested.



That's it for now. There's not enough time to reinstall the arm and get eveything balanced up. I have a two-hour drive tomorrow morning so first impressions and phase 2 coming later in the week

Well done cant wait for the report.

[MartinT]

So, I've had time to listen to Phase 1 (two-stage, SR5-27 followed by TDR-21) and I'm rather surprised as I didn't really expect this upgrade to provide any more performance over the SR5-21 alone.

In fact, there is a further refinement across the board but particularly in the midrange area and the level of the acoustic of the recording versus the surroundings, or the vividness of the presentation if you prefer. Leo summed it up rather well in post #1 as "I did notice a further layer of background muck (best way to describe it) removed".

Next stage will involve cutting the 21V PCB track and using both sides of the TDR-21 regulator.

[Reid Malenfant]

Interesting test Martin, I didn't realise you were going to try it both ways. I'd expect the seperated regulators to make the more significant difference

[Paul Hynes]

Hi Martin,

Disregarding your Power Plant, which will be quieter than direct mains connection, you have doubled the supply line rejection of mains born interference and rectification artefacts of your composite Technics power supply, which would drop the background noise level being fed to the control and motor drive circuitry. This would clean up the low-level information presentation.

The rest of the regulator mods take this a little further although the law of diminishing returns will apply to a degree with this noise reduction, as other circuit noise sources will start to dominate. The additional individual stage regulators will show a more pronounced effect on the reduction of power supply inter-modulation around the circuit power supply distribution on the motor board between the various control circuit stages and the motor drive section. This inter-modulation clutter can be considered as a noise source. Reducing this will also clean up the presentation in quite interesting ways.

Regards
Paul

[MartinT]

I have now completed phase 2 - separate 21V power supplies to the motor control and motor drive circuitry.

Showing the cut PCB track to separate the motor control (left side) from the motor drive (right side) electronics. I used a test meter to confirm that the power rails were isolated from each other. A new power wire (seen at bottom) feeds 21V to the leg of C110 for motor drive.



Reassembled into the deck. The TDR-21 dual regulator pinout is (from the rear) 1. +27V in, 2. disused, 3. disused, 4. +21V out to Motor Control, 5. 0V to chassis earth, 6. +21V to Motor Drive.



Listening to it, I am hearing interesting things. There is not much change to foreground instruments, but material in the background, deep back into the stage, is now more finely resolved. Tiny cues and things happening in the mix are now clear, what was a 'something' now becomes detectable as a cymbal, bell or other persussive sound. Overall background noise is very well suppressed and that sense of the music coming from a black background is now more pronounced.

Furthermore, and this is obvious even from another room, the Technics' metronomic pitch accuracy and timing gradually impresses on the mind as better than ever.

This is excellent, and confirms what Leo and Paul have discovered, which is that two-stage regulation and division of the noisy motor drive from the sensitive motor control is well worth implementing. The TDR-21 custom dual regulator module is a winner, all driven from the excellent SR5-27 outboard PSU. If you stop at this point, you will already have one hell of a good sounding deck.

I'm going to give it a couple of weeks now, to let everything bed in and to listen to a lot more music. Phase 3 will come later

[Marco]

Respect, and very interesting stuff, Martin! I look forward to reading more of your thoughts on these mods, in due course

Marco.