Systemdek motor driver schematic

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Standard synchronous motor PSUs are remarkably simple.

All you need is a series resistor and plase shift capacitor.

All the info you probably need is here :

http://www.neilmcbride.co.uk/ttpsu.html

note here the point is trying to run the motor at about 85VAC,
much lower than normal but with 240VAC and no transformer
the motor network is basically the same but with say 7K.

IMO I think 500VA is utterly ridiculous and 50VA would be fine,
but when your charging whatever they did for a box with one
transformer, one resistor and one capacitor I expect the
weight of the box is comforting to the gullible consumer.

:) sreten.
 
fried resistor

I have a bag of 33k 10w resistors leftover from my service engineer days. They were uprated replacements either for the systemdek electronic or the manticore manta. Unfortunately i can't remember which one!! The circuit I'm thinking of used the 33k resistor to provide a low voltage power supply for the oscillator and driver ics, the motor driver transistors being powered separately with a higher voltage. The original resistor was a 2w carbon type which failed frequently as the low votage supply was maintained all the time the turntable was connected to the mains.
I could be talking about the wrong turntable completely but maybe this will give you some ides as to where you might start looking. What you need to establish is what the resistor is for. If it's in series with the motor then it will be a much lower value. If it is dropping mains voltage to about 12v or so then a 33k would be about right.
Have plenty resistors left if you need one
 
The resistor in question is the output stage driver transistor load which turned out to be around 34k at 2W. The reissued (1989) driver board does use a 22K, 7W R to feed a zener/3 pin regulator for the clocks and filter opamps.

The hole thing is floated as no isolation transformer is used the Gnd plane being at neutral potential- very tricky if you want to test with earthed test kit so be careful.

So although you may have refered to a different model altogether your 33k was spot on.. thanks.

Any advances on where to get reasonably priced drive belts for the Systemdek IIE?

cheers
 
So your systemdek is spinning again - excellent news! I always thought that when properly set up, it could match the much more expensive linn / roksan rivals of the time especially with the acrylic platter upgrade.
As far as i know, Audionote launched their own range of decks based on the systemdek design. Might be worth finding out what they are charging for belts.
 
I bought some clear acrylic sheeting for green houses or similar.

About 2mm/2.5mm thick.
I knocked up a rig for cutting circles from the centre hole with a jig saw.

I cut three pieces 12" diameter and added a label cutout on one.

I glued the pieces together using black acrylic car paint, and used
the same paint to finish off the top surface. Polishing the edges
was a bit of a pain but I left them clear, looked quite cool.

The end result should be an acrylic mat 6mm to 9mm thick.
Of course you can add more layers to make a platter.

I reckon the acrylic mat was 7mm thick and on the SystemDek
was better than the standard felt mat. But it wasn't as good
as my Disk SE2.2 (2.2lb=1Kg) hard rubber mat - which simply
has a less bright and more controlled treble register.
(The SE2.2 has the advantage of a very subtle optimum profile.)

I think its now doing sterling duty covering up the holes on
a japanese belt drive, the ones with large platter cutouts.

:) sreten.
 
sorry to revive an old thread but does anyone have the schematic for the systemdek power supply.
I'm also wondering did this PSU supply the two phases for the motor or did it just supply one and rely on a capacitor in the turntable to generate the second phase.

Many thanks

Nicholas
 
Systemdek IIXe info...

I keep sitting down and starting to draw out the schematic for the IIXe board, but am always interupted half way through and never seem to get my head back into it!
Only 1 phase is generated on board, the second being supplied by the cap on the little board by the motor.
You didn't mention the nature of the fault that you have, but if your motor is going backwards, it is most likely the 22uF NP capacitor on the main board that has gone s/c. If its not going round at all, then it could be any number of things, but first try putting a voltmeter across the zenner next to the big power resistor and check that it is sitting at about 12v. (DO be carefull with your fingers to the left of the zener, as rectified mains can hurt !) - If 12v is missing, then power down, unplug, wait a while, then check the big power resistor first (looking for o/c), the smaller power resistor second and if the fault still isn't apparant, then just change the bridge rectifier.......it is extremely unusual for the fault to be in the low voltage electronics, or even in the switching transistors.
Hope this helps.
 
Hi Barry,
Thanks for that. Its actually the external PSU for systemdek. I've sent it back to the supplier for repair now. The turntable however was originally just a systemdek iix and someone removed the original electronics (cap and resistor i guess) and connected the grey motor wire to the power lead earth (middle pin on kettle style male plug)
blue motor wire connected to blue, (left pin on plug)
red motor wire connected to black , (right pin on plug)
and an extra piece of green/yellow wire connected to green chassis wire and hanging out the back.
The deck was spinning backwards sometimes. Oscillating back and forth when starting up and not working on 45 setting and only sometimes on the 33.

The thing is though if the external PSU only generates one phase this arrangement is never going to work.
Do you know anything about the systemdek external PSU? I wonder does it produce both phases.

Thanks
Nicky
 
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