SONY PUA-237, PUA-286 anti-skating thread/string repair

[Martin65]

Dear all,

I have inherited two wonderful SONY PUA tonearms, a PUA-237 and a PUA-286, both with a broken anti-skating thread. I would really love to fix and use them on my SONY TTS 3000 and 4000 drives.

Is anyone of you aware of an easy-to-follow repair instruction for restringing the anti-skating device on these tonearms. I would be deeply thankful for any help on this issue.

Thank you very much in advance for your help.

Best,
Martin

 

[Nat]

Usually antiskating threads are made of very fine plastic thread - I assume nylon, but what do I know?. The problem is that it is not easy to tie neat knots in this filament, nor to get the knot where you want it. I assume that is why they are often crimped, but not everyone has crimping machines to hand. Super glue seems to be a possible help, but it doesn't seem to work if it isn't applied to knotted filament, in which case, it may not be needed.
I wonder if the various anti skating threads and weights available on the internet - Project certainly sells them - might be what you need.

 

[Martin65]

Dear Nat,

Thank you for your immediate response.

The anti-skating mechanism of the SONY PUA 237/286 is rather special and quite different from the fading weight anti-skating mechanism found in most vintage SME tonearms for example.

A string (blue) is attached to a cantilever on the one side and to a bias cam on the other side. The further the tonearm moves into the center of the record, the greater the force that is applied via the bias cam to the bias sensing cam and therefore to the tonearm.
It's a real pain replacing the string. So far, it has taken me numerous attempts, but the length of the string is just not right yet.

Best,
Martin

 

[Nat]

Hmm - that looks like more of a pain than the standard hanging weight type of antiskating that isn't just a spring or weight on a stick. My comments about the difficulty of making knots in the filament are still relevant, as you have found.
Do you have the old, broken pieces of filament? Can you but the broken ends together, tape them down and then measure the needed length?
Are the ends of the filament loops around posts, or some sort of lump to trap the filament after it goes through the part?
And it occurs to me that we use a simple type of crimp at work for wire wound heaters, which is simply a small diameter copper tube that you crush over the wires or filaments with needle nose pliers if you don't have just happen to have actual crimping tools at home. You'd need a very small diameter tube, but I think jewelery makers (and bead bracelet hobbiests) use them and you might be able to find what you need at a crafts store or on line.
I would think that, depending on access, rather than trying to measure and get the length right, you might be able to attach the filament at one end with a crimp and then put the other end in place and snug it up and then crimp.
Good luck