Not Dirty Vinyl ... Dirty Turntable

analog music reproduction discussion

Not Dirty Vinyl ... Dirty Turntable

Postby TomMcNally » Wed Aug 31, 2011 8:17 pm

New addition to my already overloaded domicile ... a Technics SP-15
turntable in factory base with Audio Technica arm.
I have two, the other one has a common problem, a blown
and supposedly unobtainable chip that makes it spin at 80+ RPM
out of control.

It needs a little cleaning up, and polishing to remove the
salt air pitting. I have the factory dust cover too, but it
has a big chunk out of it.

There were some guys trying to come up with a new-tech
alternative controller for the motor, I need to google around.

Image
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Postby Quad » Wed Aug 31, 2011 11:31 pm

Nice!
Steerpike from South Africa was working on a SP-10
controller, but he hasn't posted any updates in
a while -

http://www.diyaudio.com/forums/analogue ... ation.html
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Postby Shannon Parks » Thu Sep 01, 2011 6:19 am

Nice score, Tom!

One of my projects is rebuilding the timing circuit of Chuo Denki BD5200. I hope to get to that this winter.

Shannon
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Postby TomMcNally » Thu Sep 01, 2011 10:13 am

Thanks for the link Quad ... I saw that a few years ago but couldn't
remember where it was.

Sounds good Shannon. I have "several" bad Technics TT's that
need the controller fix, not sure if my limited BASIC Stamp
programming experience would be of any value in coming up
with a fix.
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Postby nyazzip » Thu Sep 01, 2011 8:07 pm

wonder why the chips fail...? modern 124v AC "standard"?
<i>the poor craftsman blames his tools</i>
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Postby TomMcNally » Thu Sep 01, 2011 9:04 pm

From what I've been reading, Technics used a chipset for speed
control consisting of consists of the AN640G (IC101, Drive), AN660 (IC202, Control), DN860 (IC203, frequency Divider) and the µPC4558C (IC201, FG-amp) and apparently they were so prone to failure, that there
was a special section added to the service manual on how to repair
them. Of course, now that the turntables are 30 years old and the
source for the chips has dried up, not much can be done, short of
re-inventing the thing.

They were designed to work on 120 vac 50 or 60 hz ... so I don't think
it's a power line issue.
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Postby Geek » Thu Sep 01, 2011 9:11 pm

Heh, other than the 4558 which is still hanging around, I can't even cross the others (???)

Cheers!
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