Technics SL-1200 DC Power Supply

[6L6]

Oh jeesh no... Keep the motor supply far away electrically from the PSU for the Pearl.

Just re-use the Technics transformer for the TT.

And anyway, the Pearl(1) PSU needs more than a 20VAC transformer, IIRC...

 

[Eric]

Thanks for the insight, Jim. I was looking to minimize the number of little power supply boxes I would have floating around. The outboard supply for the Pearl 2 uses a 200VA transformer with dual secondaries, so there is plenty of power available. It lives in a 17" by 12" box, so I suppose I'll just put the TT transformer and another CRCRC filter in the box next to the supply for the Pearl.

 

[6L6]

If the BOX is that big, I could see having two supplies in the same box, separate only but in the same enclosure, but that may lead to earthing issues, maybe...

 

[Eric]

Here are a few images of my new outboard PSU for the SL-1200. I removed the transformer and put it in the box with my Pearl PSU - it provides two 21v lines that each connect back to the CRCRC in the outboard box. Two 21v tracking-preregulators go in the hole left by the transformer. It took a little trial and error to cut, drill, and test fit the copper bar that holds the regulators. It measure 1/4"x1" by about 3.5". A heat sink is definitely needed for the regulators. After a little while, it gets to just above body temp. I de-populated the onboard power supply section, cut the trace to separate motor control from motor driver and then put the new PSU in. One last test before connecting the power to the PCB, and it's all back up and running. Haven't had much time to evaluate yet, but the platter comes to rest more quickly after hitting the "start/stop" button with the new PSU.

I cut the wires to the on/off switch and used this to control the LED strobe.

I still have a bit of broad-spectrum hiss to solve with my Pearle (audible with the preamp volume set to 0dB), and then its on to finishing the BA-3 remote preamp...

 

[dubiella]

Hello 6L6 and to everyone else,

I have just completed my outboard power supply and have a question concerning the correct voltages:

Before installing it into the turntable I checked the voltages and got ca. 31 Volts from the transformer and ca. 41 V after rectifier and CRC - caps.
For now I have kept the stock regulator.

Since this seemed to be correct I installed it and checked the values again in the circuit.
I measured ca. 33 VDC at the point where the umbilical cable enters the board.
Is this still correct or a bit on the low side?
All other test points show the correct values of 5, 9 and 20 VDC.

Thank you very much,

Marc

 

[yngvejos]

Sounds right. I just built external psu for my 1210 and got around 44vdc without load and it dropped to 33v or something with load.

 

[6L6]

The 33VDC is good. Everything should work fine.

 

[dubiella]

Thanks.

So the next and final step will be the regulator.

Does the KAB DC-1200 offer any advantage over the one published here?
It says it "mirrors the same slow turn on waveform of the stock power supply".

Is this necessary or beneficial?

I would be willing to pay for the KAB design if it is better. Otherwise I would be happy to build my own regulator.

Once again: thank you very much for this project!

 

[Calvin]

Hi,

You can use a simple integrated Regulator like the LM317.
Just make sure that the input voltage stays below the 37V input voltage limit of the LM317.
In the SL-1200mkX only the motor driver IC is supplied with the 21V from the regulator.
The other chips are supplied with 12V, that are generated by one of the chips together with an regulator transistor.
So there's no need for a complicated super regulator at all.

jauu
Calvin

 

[6L6]

KAB has a nice design and good PCB, it's a solid solution. Is it "better" than a simpler solution? I don't know, but it is certainly better than stock!!

 

[6L6]

Bump.

Anybody modding their -1200's lately?

 

[weust]

I bought a VPI Classic 3 about half a year ago.
The SL-1210 is not in use right now.

 

[qwertyl]

Bump.

Anybody modding their -1200's lately?

On my To Do list. Probably after I finish my BA-3 pre/power amps...

 

[Eric]

Ha - still enjoying all of the mods I did last year. I did happen to build one more thing, more of an accessory than a mod to the table itself. A DIY static control brush. Haven't had a single issue with static build up since I installed it!

 

[davefl]

I like the brush idea, very cool. Static was always the biggest problem with my acrylic platter TT.

 

[dimkasta]

Bump.

Anybody modding their -1200's lately?

Unfortunately during my last psu changes I have fried my motor controller chip and have been neglecting getting a new one

 

[6L6]

Oh. Bummer.

 

[mortron]

Bump.

Anybody modding their -1200's lately?

I have a pair of SP25's that require some TLC. I am tempted to work on them over the winter (recapping, moving PSU). Just not sure if I do both at same time or what.

 

[6L6]

I'd move the PSU and recap all as the same project, although if you want to split it up, do the PSU first.

The SP-25 is a great table, do you have any plinth ideas?

 

[mortron]

I'd move the PSU and recap all as the same project, although if you want to split it up, do the PSU first.

The SP-25 is a great table, do you have any plinth ideas?

I do not have any plinths planned. Seen quite a few.

As for the PSU and recap, I would do it as one project... but do I do both SP25's at same time lol. I wish I bought new bearings when kab USA only charged $30 per.

I'm finishing up a Lenco, but already thinking direct drive is my bag. Always had good luck with em.