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PostPosted: 01 Jul 2016, 14:38 
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Location: Milwaukee, WI, USA
Hello everyone,

I am new to this forum, therefore a quick introduction to myself:

My name is Erik, I live in Wisconsin, USA but am originally from Germany.
I collect Vinyl and am at the moment in the process of building a vacuum record cleaning machine.

The driving part of this RCM will be a SONY PS-LX2 which I gutted until only the motor, trafo, platter speed control and several switches were left.

Does anybody here by chance know, how to tweak the electronics so that I could change the direction of the platter spin with a switch?
I already tried to reverse the 2 cables I thought were power line to the trafo (red circled, one cable is orange, one white) but with no effect. Platter still spun clockwise.
The green circled cables might be the solution, but I am not entirely sure.

Thank you a lot,

Erik


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I love vinyl. Projects:
- build a DIY RCM
- build some sandbox rests for the equipment
- build some bass traps and damping board to improve room accoustics


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PostPosted: 02 Jul 2016, 10:36 
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You won't be able to change the direction from the AC (transformer side) of the circuit. It would need to be done at the motor on the DC side of the power supply. However this table has an optical servo system which might be a problem if the table is running in reverse.

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PostPosted: 03 Jul 2016, 09:19 
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Hello blackdog,

Thank you very much for your reply.

As far as I could see, the turntable has a magnetic speed control, not optical. But you are right, this might cause some issues. Will have to try and find out I guess.

But when your write on the DC side, that would then be from transformer to PCB, right? So I need to switch the cables that are marked with a green circle in my picture, or am I missing something? Would you happen to know which ones exactly or how to find out?

Thanks again and have a great Sunday,

Erik

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I love vinyl. Projects:
- build a DIY RCM
- build some sandbox rests for the equipment
- build some bass traps and damping board to improve room accoustics


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PostPosted: 06 Jul 2016, 07:06 
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Even the the ones you have marked are on the AC side. That is the secondary of the power transformer. Reversing those will do nothing.
There should be a small bridge rectifier or 4 small diodes on the board. That's where you need to start looking. How is the motor itself hooked up to the board? Do you have the schematic?

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PostPosted: 07 Jul 2016, 15:20 
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Yes Blackdog is right. The AC goes into the transformer, (which reduces the voltage down), then it is rectified into DC by the diode rectifier, then filtered by the capacitors to provide pure DC for the circuitry that drives the motor. It is the OUTPUT of this drive cct going to the motor, that would be changed to make the motor go in the reverse direction. Be aware though the cct must see the DC as it already does so do not change it's polarity. The polarity change must be made at the output of the cct TO the motor. If at all possible please provide a schematic diagram for the drive cct board.


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PostPosted: 08 Jul 2016, 02:12 
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http://www.vinylengine.com/library/sony/ps-lx2.shtml

"Control system: magnedisc servo control"

I'd say restore it, use it as a decent table and get a P.O.S. plastic-junktastic to turn into a DJ table with reverse spin. Value Village, Goodwill, Sally Ann or a local record store.

Cheers!

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PostPosted: 08 Jul 2016, 10:45 
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Location: Milwaukee, WI, USA
Hello everyone,

thank you all for your responses.

@ Blackdog, laurie54:

I unfortunately do not have a schematic diagram, but I posted 2 pictures taken from the board. In red are
1. (front of the board) the cables from the AC transformer incl. what might be the 4 diodes
2. (back of the board) power connection from the board to the motor.

@Geek:

Thanks for the idea. But I intend to turn the turntable into the driving part of a vacuum record cleaning machine (RCM). That's why I actually dismantled it. I am happy with my current turntable, so no need to replace it with a Sony. But I have to say, I am intrigued by the idea of restoring a turntable later on. Might be a neat project.

Cheers,

Erik


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I love vinyl. Projects:
- build a DIY RCM
- build some sandbox rests for the equipment
- build some bass traps and damping board to improve room accoustics


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 Profile  
 
PostPosted: 08 Jul 2016, 13:12 
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Ahhhhh, I see! :D

You'll need a motor with some serious torque. I know that TT you have and it will stall. Heck, the ones I repair will stall under a cabon fibre brush, sans vacuum :eek:

Also, you'll need to keep the record on the platter under scrub... either clamp (easiest) or a vacuum system under the platter (like an air hockey table, only suction).

Awesome project, good luck!

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* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


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PostPosted: 08 Jul 2016, 13:22 
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Joined: 01 Jul 2016, 14:25
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Location: Milwaukee, WI, USA
Hey Geek,

thanks for the help...atm I will sue a clamp. It's easiest since I have a Michell clamp around.

Regarding torque, it doesn't seem to have that low of a torque when I fired it up, but I'll see when the vacuum is attached. :)

Cheers,

Erik

_________________
I love vinyl. Projects:
- build a DIY RCM
- build some sandbox rests for the equipment
- build some bass traps and damping board to improve room accoustics


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 Profile  
 
PostPosted: 08 Jul 2016, 13:48 
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Joined: 09 Oct 2012, 19:43
Posts: 284
Location: Vancouver Canada
OH pics are helpful to. Still a bit fuzzy with pics, but it looks to be a stepper motor and the drive transistors are marked as "Q106,7,8,9". These are providing the power to the motor coils. They are arranged in what is called an H-Bridge configuration. The control board switches Q106-9 in pairs of two at a time, routing plus to one side and minus to the other then switching them oppositely. Alternating from +/- to -/+. This is where the mod/change would be most easily made. To get a firm grasp on how this works do a google search for "stepper motors" and their drive cct's. It's not rocket science just unknown to most but you will quickly catch on to how they work. Basically there are two types. Bi-polar and Uni-polar. A quick look see at the two types of stepper motors and how they work will make it clear to you which you have and what you need to do to accomplish what you want. Do not jump the gun and switch wires though. Educate yourself on how they work, which one of the two you have, then step forward and solder. It's always best to have a flashlight when walking down a dark hallway. It could just be a dark hallway. Or it could be a dark hallway with an open well in the middle of it!
I must ask why spin in the opposite direction? Does the dust/dirt come out better?
Also i see red, white/blue, and white/red wires on the left side of the pic. What do these go to. Are they the sensor wires and the speed control pot?


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