Sony ps-636 tone arm lowering to fast,help appreciated

[Newzealand]

Hi there all

I got this turn table with a few problems,

I recapped the power supply as the caps had been very hot by the looks,


I have repaired the tone arm voltage off set for horizontal movement,
The table operates as it should using the controls,

It also suffered from platter spinning out of control with x-tal in the off position,
This I repaired by disassemble of pot and a good cleaning

It has two more problems that I'm about to tackle,
The frist is the tone arm drops hard and rises the same,
It has a electro magnetic system for arm movement,
The arm rises and falls as needed but with no damping at all,
Does any one have a idea where to look frist? I have a multi meter and a digital osiliscope and most other stuff like soldering iron etc
Any input would be great,

I have mentioned this in another thread but thought it would be best to start a new one

Mike

 

[EngineerNate]

The tonearm lowering is likely supposed to be damped by high viscosity silicone grease. You can get replacement stuff from rc hobby sources as rc car shock oil. Do some searching to see what grade Sony typically used, if you can.

 

[Chrispy]

Agree that you're likely looking at that part of the mechanism engineernate mentions.....which causes problems in many cueing levers in many brands. Some are easier to deal with than others...

 

[Newzealand]

The tonearm lowering is likely supposed to be damped by high viscosity silicone grease. You can get replacement stuff from rc hobby sources as rc car shock oil. Do some searching to see what grade Sony typically used, if you can.

I was thinking of that,however I own a few sony tables and when they lower and rise the arm it's a controlled lift or fall via the magnetic system,do you think this model does not have that feature?
Mike

 

[Newzealand]

It does use a eletro magnetic lifter

 

[Newzealand]

The others I have use the bio tracking arm,
I have got some of the oil you speak of,I just don't want to put it in and have to clean it out if not any good,
I guess I can disassemble it and apply the silicone oil,

 

[Newzealand]

The others I have use the bio tracking arm,
I have got some of the oil you speak of,I just don't want to put it in and have to clean it out if not any good,
I guess I can disassemble it and apply the silicone oil,

I have tried the oil,big fail really, very little difference but now have a clean up,
I'll keep studying the schematics, I have changed out all the caps,
I might go ahead and order the transistors that operate the arm in the vertical position and just charge them all out,
Then I'll start on the ic's guess if that does not work,
Even with a very heavy weight on the head shell it comes up like a rocket,

Mike

 

[NTK]

The lifter is actuated by a solenoid. The speed of the solenoid is proportional to the drive voltage.
Figures from: https://www.manualslib.com/manual/975940/Sony-Ps-636.html?page=16#manual

 

[Newzealand]

The lifter is actuated by a solenoid. The speed of the solenoid is proportional to the drive voltage.
Figures from: https://www.manualslib.com/manual/975940/Sony-Ps-636.html?page=16#manual
View attachment 516322
View attachment 516323

Thanks for that,
Could I trouble you to give me your thoughts on which component might be at fault in the diagram? It falls and rises fast ,
Q421 maybe?

 

[Newzealand]

The lifter is actuated by a solenoid. The speed of the solenoid is proportional to the drive voltage.
Figures from: https://www.manualslib.com/manual/975940/Sony-Ps-636.html?page=16#manual
View attachment 516322
View attachment 516323

Or c424 maybe?
This is a very complex machine and I know only very basic electrical knowledge, but learning slowly

 

[Palmer]

NTK - awesome to post the diagram... I would think that Silicone fluid is still a factor in the dampening of the movement, a solenoid is not exactly a servo motor. I'd get some 60k or so, my experience with purely spring loaded lifters.

Cheers

 

[NTK]

Or c424 maybe?
This is a very complex machine and I know only very basic electrical knowledge, but learning slowly

Sorry. My background is in mechanical engineering and my understanding of electronics is very basic. Based what I understand I am guessing capacitor C424 does affect how fast the voltage supplying the solenoid ramps up, and therefore its speed.

Hopefully someone more knowledgeable than me will be kind enough to chip in.

 

[Newzealand]

Sorry. My background is in mechanical engineering and my understanding of electronics is very basic. Based what I understand I am guessing capacitor C424 does affect how fast the voltage supplying the solenoid ramps up, and therefore its speed.

Hopefully someone more knowledgeable than me will be kind enough to chip in.

Thanks,very helpful, I thought the same thing,I added some damping oil to the shaft and it has helped,but still looks fast to me,
I'll replace 424 and see how it goes,I tested 424 in place, it reads 12uf ,it's a 10uf ,I wonder if that's enough to cause problems, I doubt it some how, I'll pick up a new 10uf and fit in case
Thanks for your help
Mike