Technics SL 1200 Turntable Power Supply

[russtafarian]

I have a Torroid in a case which puts out 18v AC secondaries - I may give it a go. I've noticed a voltage drop of a couple of volts on the 30v secondaries when the platter starts so a bigger transformer even with a lower output may not even drop the voltage?

Would this be for a new regulator or the stock regulator? 18vac will work for a LM317 but may not be enough voltage for the stock regulator circuit. I don't know for sure because I haven't tried it, but it's a potential issue to consider.

Russ

[resu]

The russtafarian PSU mod is really tempting, or would be if only I had someone to do it for me. For my own abilities it is a bit too risky business

So something different but still staying on the topic:

I would like to ask if someone of you knows anything about the Mains-Cables-R-Us Technics SL1200/1210 Linear Power Supply?
It consists of 2 cases, a main larger case and a smaller case that contains the final regulation stage. The smaller case can be put inside the turntable in the space where the old PSU fits.
If the installation instructions supplied are clear enough this could be something I'd venture to undertake. Maybe some others too?

[Trackside]

I have a Torroid in a case which puts out 18v AC secondaries - I may give it a go. I've noticed a voltage drop of a couple of volts on the 30v secondaries when the platter starts so a bigger transformer even with a lower output may not even drop the voltage?

Would this be for a new regulator or the stock regulator? 18vac will work for a LM317 but may not be enough voltage for the stock regulator circuit. I don't know for sure because I haven't tried it, but it's a potential issue to consider.

Russ

Ah - I failed to understand this was for the LM317

[brainf]

Do I understand correctly - there TWO (2) regulators in the power supply stage and Russ's tweak only replaces one of them?

[russtafarian]

There are multiple regulation stages for various control circuits in the SL1200. Upgrading the primary regulator ensures that the rest of the control circuits receive clean, low noise +21vdc with plenty of current capacity for platter startups.

For those wanting to go all out, Paul Hynes has developed an awesome SL1200 PS that independently regulates the voltage for each circuit.

Russ

[brainf]

There are multiple regulation stages for various control circuits in the SL1200. Upgrading the primary regulator ensures that the rest of the control circuits receive clean, low noise +21vdc with plenty of current capacity for platter startups.

For those wanting to go all out, Paul Hynes has developed an awesome SL1200 PS that independently regulates the voltage for each circuit.

Russ

Thanks for the confirmation Russ! Your approach - upgrading the primary regulator only - makes more economical sense and is practical.

cheers.

[valvehead]

I'd like to DIY a PSU for my SL-1200 also. Having seen pictures of the inside of the Time-Step PSU (a very pricey item) I was shocked to see what appears to be the standard textbook LM317 circuit, with the regulator inside the casing - not a good move. That regulator needs to be inside the deck as per the original.

Can we do better than an LM317 for DIY purposes, and without getting too expensive? I too just want to remove the transformer to an external enclosure, and upgrade the primary regulator only.

- John

[russtafarian]

Can we do better than an LM317 for DIY purposes, and without getting too expensive?

I asked the same question. I found that most regulators used for audio circuits can't handle the SL1200's 40+ vdc input from the rectifier, but the LM317 will. I went with Linear Tech's LT317 which is a drop in replacement with performance closer to their popular LT1084-85-86 regs. At $4 ,the LT317 is 10X the price of a 40 cent LM317. I hope that's not too expensive for you.

If you go with a different transformer, one with a 18VAC secondary and 2 amps of current capability, the rectified voltage drops to around 25vdc (18 x 1.414). With that you could use a LT1085 or similar regulator.

I looked at the internal PS that Paul Hynes is offering for the SL1200. Since the motor drive demands the high current, not the control circuitry, he separates the two circuits and gives them each their own regulator. That makes a lot of sense.

Russ

[blueworm]

I Agree with the theory that the regulator is better served up close to the load.

I made a LM317 based on Tangent (head-fi) STEPS this was several years ago, less than 100 EUR in parts. I kept the umbilical short about 40cm. I really dont think that I would be able to hear the difference between those 40cm of cable.

The Paul Hynes power supply seems fine and dandy. The price and the law of diminishing returns will both slap you in the mouth like a wet cod.

Russ your approch seems to me like the best way to do it, perhaps a small pcb surface mount components to keep everything nice and small.

[valvehead]

Is it best to externalise both the transformer, and rectifier, or would slightly better performance be gained by having the rectifiers next to the regulator inside the deck? I'll be using the LT317 as suggested by Russ.

[russtafarian]

Is it best to externalise both the transformer, and rectifier, or would slightly better performance be gained by having the rectifiers next to the regulator inside the deck?

Theoretically it's better to keep the noisy rectifiers away from the circuit but I don't think it's a big deal either way.

Russ

[valvehead]

Is it best to externalise both the transformer, and rectifier, or would slightly better performance be gained by having the rectifiers next to the regulator inside the deck?

Theoretically it's better to keep the noisy rectifiers away from the circuit but I don't think it's a big deal either way.

Russ

Cool I was going to put them into an external enclosure along with the mains transformer anyway. Would it be wise to add a cap or two on the rectifiers output? Say 10,000uF or so?

Cheers,

- John

[russtafarian]

I guess it depends on how far you want to take it. Using the stock rectifier the way I documented is really easy to hook up. If you want to build a complete external DC power supply with rectifier and filter cap, that's fine too. You will still need a cap on the input of the regulator circuit. See the LM317 data sheet for specifics.

[cafe latte]

There are multiple regulation stages for various control circuits in the SL1200. Upgrading the primary regulator ensures that the rest of the control circuits receive clean, low noise +21vdc with plenty of current capacity for platter startups.

For those wanting to go all out, Paul Hynes has developed an awesome SL1200 PS that independently regulates the voltage for each circuit.

Russ

Except the regulator being in the external box which is never a good idea even with a 40cm hook up to the turntable. How much is the Paul Hynes psu anyway?
Regards
CL