The next Technics project... SP-10

[6L6]

Three, actually, there's 140V required to light the strobe. In addition to the 5V for the logic and 32V for the motor.

But yes, there is nothing complex nor particularly special, other than 3 voltages in one PSU.

[6L6]

I started the re-cap procedure, it's all very straightforward. There are some things that need repair on the PCB, I.E., the fixing of poor repairs... But nothing major.

More photos as I progress.

[6L6]

I've completed the re-cap on one of the boards (save for one cap I didn't realize was a bi-polar electrolytic, so I need to order a few of those...)

When I get into the remainder of the 2nd board I'll grab some photos.

It's a straightforward process, and although the PCB are thin with thin copper, it's made up for by there being silkscreen on both sides of a single-layer board.

[RochaCullen]

Great project.

I would dearly love to undertake something similar in the not so distant future. All the best with it, and hopefully you can get that nick out of the platter. I winced when I saw that!!

[6L6]

The nick is staying. I would suggest not wincing, it can be painful.

[Qwin]

[6L6]

So once opening the table up and getting to the solder side of the PCB I find one things that are less than optimal... This being the worst offender. There was power resistor replaced on the board, and on this table it was made by somebody badly connecting 2 resistors in series. When they did this the traces lifted and this mess was made.


Here's the new resistor, with bends in the leads to let things heat up without stressing the PCB any more. (In this photo it looks like the bend blocks the pot - it's only camera angle, and the pot is easily accessible.)





Luckily there was a few unused holes in the PCB where it could attach, and the lift trace could be left completely alone.


Ok, this one is all my fault... It's a very fragile board, 31yr old, with surprisingly thin copper. Luckily there is a few places where I could re-attach the lead and make the circuit.


The board with beautiful new caps.


Dead soldiers



With the PCB off I can see the production date of the motor. I was in 3rd grade of elementary school that day.

[6L6]

Lots of activity on this thread at diyAudio - the guy who talked me into this is making wonderful progress, and another friend has gotten one as well.

See here -

http://www.diyaudio.com/forums/analo...ml#post4063701

And post #59, and post #69

Their tables are Mk2, not Mk2A, but the mechanicals are identical.

[6L6]

Platter Mat -

Taking the advice of very warm water, a bit of detergent and letting it soak, the glue residue is almost entirely removed. There is still some damage to the rubber itself, but it's almost all cosmetic.

The two mats are photographed to show the damage. In general, they look pretty nice.

[6L6]

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.