SL-1200 DC Power Supply DIY

[6L6]

That all sounds really neat! I'd love to see some photos and schematics if you have any.

[Ianmac]

That all sounds really neat! I'd love to see some photos and schematics if you have any.

Prototype.
just about to start a tidy up for the final version.
The two sub boards in the top right will be one board slightly smaller .
REgs on the left in the trf hole will be sitting horizontally with the regs vertical. I have to make a new base to hold them with enough aluminium on the vertical to mount the regs. I have to improve the input connection.
Parts are en route from farnel UK.

[Ianmac]

Main reg board on plate to fit into the transformer housing.[IMG][/IMG]
Noise on Scope-- less than 1mv pkto pk [IMG][/IMG]to Pk
noise spectrum to 3Mhz[IMG][/IMG]

Is anyone interested in a DIY improvement to their Techie ??

[RobbieGong]

Good on you Ian, impressive stuf you are doing

[dimkasta]

Is anyone interested in a DIY improvement to their Techie ??

Are these with the motor running?

[Ianmac]

No, both main regs on soak test loaded to 500ma and subs to 100ma.
Im trying to buy a damaged platter so I can machine it and weight load it to be a motor section only and scope the innards with the mini platter/motor running. Unfortunately Platters are being sold for silly money on Ebay.
Im away for a few days but when I get back ill try and get two wires out of my deck and give you some more figures. I will also be modifying a second deck to this spec when I get back.

My own earlier PSU was transformer rectifier box with unreg DC fed to my regulator fitted in the old transformer housing. Anyone with a similar set up need only build another reg and split feed the supply to Control and Motor.
The sonic improvement I am getting makes this mod well worth the effort.
Thanks for your pointer to the Cmos chip.

[dimkasta]

Why don't you pass the probes through the power cable holes? They should stay nicely under the platter with some duck tape.

[dimkasta]

OK 3 and a half years later, let's do some work on Jim's original design.

It's time to get rid of that semi-random 220nF snubber and replace it with a proper actually working snubber, measured for the actual stock SL1200 transformer.

To do that, I used the Quasimodo jig designed by Mark Johnson at diyaudio.
http://www.diyaudio.com/forums/power...-test-jig.html

Here is Mr Q banging the stock transformer like a salvation army drum

q1.jpg

This one is with the snubbing circuit in place. Still not perfect, but looking good.

q2.jpg

Here I have gone too far and overdamped the thing

q3.jpg

And here it looks about right. No signs of ringing.

q4.jpg

Zooming a bit to verify it. Again, no signs of ringing.

q5.jpg

The juice/schematic/values on the next post because I cannot upload any more images on this one

[dimkasta]

The snubber schematic is this

crc_snubber.jpg

Values are

Cx: 10nF
Cs: 150nF
Rs: 270R

Caps were red wimas, and R should be 0.5W non inductive.

This is for a primary wired for 230V.

For 110V the Rs should be a bit lower. I am too tired now to look for the wiring diagrams to rewire the transformer for 110V.
If someone can tell me how to rewire it, I will try to get some time tomorrow and get an accurate measurement for 110V too.
In the meantime, something like 250R should be a good starting value to help you evaluate this mod

Unfortunately the motor ICs are not yet here so I cannot test it myself and report any sound changes.
I promise I will report back as soon as I get the turntable up and running.

[Mike_New]

I believe Paul also discussed this subject in his posts on DC power supplies about 3 years ago.