The next Technics project... SP-10

[6L6]

Testing -

So the general setup for testing is as follows,

1) Remove PCB screws and a few other assemblies from the position under the chassis,
2) prop table up, let PCB onto tabletop,
3) get service manual (on computer) and schematics at hand,
4) have at it.



At this point all I am am doing is comparing waveforms and parameters from the schematic to what I measure in real life. So far this looks rock solid.

Some random photos -


33RPM drive speed good


Quarts crystal frequency is exactly what it's supposed to be

[phonomac]

Hello Jim,

PSU -
Here's an interesting story, sorry no photos, and this is probably the most eye-opening thing about this project thus far;

The PSU requirements are fairly benign - there are 3 voltages, all with a common ground,

5V (15mA) This is the logic supply
32.5V (250mA) Motor supply
140V (7mA) To light (but not control) the strobe

Now looking at that you see nothing at all out of the ordinary - and to get things to work, the strobe doesn't need to light up.

SO... why not hook it up to a two-channel regulated bench supply? One output at 5V, one at 32.5V. Easy.

Well, not so much... With three different supplies, a linear HP, a big switcher chinese thing, and a big linear Lambda, all three PSU were not able to drive the motor. It must be too inductive a load or something similar. The HP made the speed just run away, the lambda it ran fast, and the switcher was just massively confused as it was trying to relay through whatever voltage it though it was supposed to supply, at which time I unplugged the table.

These results were identical for both of my tables.

Both tables run fine on the Technics supply.

You must be doing something wrong somewhere. My test set-up of an SP10 Mk2 works perfectly on a bench supply which has a fixed 5V channel, and two variable ones which combine to give the 32.5V. As I assume you did I ignored the strobe since it isn't needed for anything other than as a gizmo. With the timing and PLL set up correctly it holds speed exceptionally well measured with an independent Key-Strobe unit. And makes excellent music as well

regards

Angus

[6L6]

You must be doing something wrong somewhere. My test set-up of an SP10 Mk2 works perfectly on a bench supply which has a fixed 5V channel, and two variable ones which combine to give the 32.5V.

I agree that something isn't right... I just am not sure what.

It's actually great news to hear that your deck works on a bench PSU.

[phonomac]

I agree that something isn't right... I just am not sure what.

It's actually great news to hear that your deck works on a bench PSU.

Hello Jim,
I thought overnight that I could have phrased my message better I should have said that there was something wrong somewhere - not that it was you. However the good news is that a bench supply does indeed work. The load of the motor is seen by the drive electronics, so shouldn't be reflected to the power supply. On the Mk2 the 32.5v supply runs at 0.2A when the platter is stationary, pulses slightly up when the deck starts, then drops to 0.07A when the platter is running at stable speed. Apart from a fault/wrong setting on the electronics the only other thing I can suggest to check is that the power supplies you are using aren't current limiting prematurely.

Hope you get it sorted.

regards

Angus

[6L6]

Some of you may have heard of the SP-10Mk2 PSU that Wayne (Colburn, who designs everything but the power amps) made for in-house use at Pass Labs.

One has seemed to have gotten out of that house...



(No, it's not completely stuffed, I need to make a Mouser order)

This will get a gorgeous chassis from Landfall Systems.

I still need to design and build another from scratch, but chatting with Dave Cawley as well as Wayne, I have a very solid idea of how to proceed. But I doubt it will be as completely cool as this one.

[pure sound]

Looking good. I ordered & received a couple of those replacement bearing caps but haven't fitted one yet. It'll be interesting to see what that brings.

[6L6]

I am looking forward to opening up the bearing and using the custom oil that I have gotten from a friend who is a professional chemist. (And avid audio DIYer...)

Anyway, I've gotten the Pass Labs PSU board stuffed and adjusted, it works beautifully.

The transformer for making the strobe voltage is bad, it has an open primary, I'll order another and post photos when I get it all set properly.

Next, making a PSU myself.

[6L6]

Pass PSU chassis -

This is from Landfall Systems, http://landfallsystems.com/ it's absolutely wonderful. I'll post some more photos when it's complete.

[6L6]

More photos -


Back. 4-pin XLR for power output, IEC, power switch.


Front. Switch for output relays.








My preferred power indication, place a very bright blue (it's a Pass Labs design, after all...) LED in the chassis aimed towards the vent holes. I think it looks a teeny bit like Cherenkov radiation -- Cherenkov radiation - Wikipedia, the free encyclopedia

[Spectral Morn]

Fabulous work Jim


Regards Neil