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From: William R. Walsh on 3 Jun 2010 14:54
Hello all...

I recently cleaned up and restored to working order a Sony PS-LX520 linear
tracking turntable. After that it played beautifully until two nights ago
when I turned it on and found the "start" control to be unresponsive. As it
turned out, the lights that normally come on to indicate speed and playback
mode were also dead. It had been playing beautifully the night before.

The only sign of life was from the power button and the light bulb that is
used to tell the turntable how big the record is. The table motor was trying
to run, turning the platter very slowly. No part of the control panel works.

I popped it open and had a look inside to see if I could find anything
obviously wrong. Nothing was obviously distressed. There are three different
boards: one for audio, one for the logic control and a power/speed control
board. Power comes into the unit from a multi-tapped transformer, and this
seems to be OK. Markings on the logic circuit board seem to indicate that
there should be -16 volts, +16 volts and +6 volts from the speed
control/power board. I have the two sixteen volt supplies and they are very
close to being dead on. The six volt supply is completely missing! Most of
the connectors are point to point wiring, with the wires placed into plastic
guides and soldered to the board. As they look difficult to remove, I have
not attempted to see if something is loading down the +6 volt supply.
Nothing is getting hot.

I have a service manual coming. Already I have been looking at the two
filter capacitors on the power/speed control board. They are both 25 volt,
1000uF units. One holds its charge nicely and long after power off. The
other one discharges much more quickly, but not quickly enough to make me
think that a problem is draining it.

Every date code in the unit suggests it was made around the middle of 1987.

Has anyone worked on this turntable or a similar model and seen this
problem?

William


From: Mark Zacharias on 4 Jun 2010 08:41
"William R. Walsh" <newsgroups1(a)idontwantjunqueemail.walshcomptech.com>
wrote in message news:98OdnSpoGZX3Z5rRnZ2dnUVZ_gGdnZ2d(a)mchsi.com...
> Hello all...
>
> I recently cleaned up and restored to working order a Sony PS-LX520 linear
> tracking turntable. After that it played beautifully until two nights ago
> when I turned it on and found the "start" control to be unresponsive. As
> it
> turned out, the lights that normally come on to indicate speed and
> playback
> mode were also dead. It had been playing beautifully the night before.
>
> The only sign of life was from the power button and the light bulb that is
> used to tell the turntable how big the record is. The table motor was
> trying
> to run, turning the platter very slowly. No part of the control panel
> works.
>
> I popped it open and had a look inside to see if I could find anything
> obviously wrong. Nothing was obviously distressed. There are three
> different
> boards: one for audio, one for the logic control and a power/speed control
> board. Power comes into the unit from a multi-tapped transformer, and this
> seems to be OK. Markings on the logic circuit board seem to indicate that
> there should be -16 volts, +16 volts and +6 volts from the speed
> control/power board. I have the two sixteen volt supplies and they are
> very
> close to being dead on. The six volt supply is completely missing! Most of
> the connectors are point to point wiring, with the wires placed into
> plastic
> guides and soldered to the board. As they look difficult to remove, I have
> not attempted to see if something is loading down the +6 volt supply.
> Nothing is getting hot.
>
> I have a service manual coming. Already I have been looking at the two
> filter capacitors on the power/speed control board. They are both 25 volt,
> 1000uF units. One holds its charge nicely and long after power off. The
> other one discharges much more quickly, but not quickly enough to make me
> think that a problem is draining it.
>
> Every date code in the unit suggests it was made around the middle of
> 1987.
>
> Has anyone worked on this turntable or a similar model and seen this
> problem?
>
> William
>
>

Not sure it was this model, but they had some problems with 100uF 16 volt
caps shorting on some of these and causing the problem you describe. Might
have also opened an IC protector, IIRC.

Mark Z.

From: William R. Walsh on 7 Jun 2010 12:46
Hi!

> Not sure it was this model, but they had some problems
> with 100uF 16 volt caps shorting on some of these and
> causing the problem you describe. Might have also opened
> an IC protector, IIRC.

Well, I was barking up the wrong tree at first. I replaced the two 25V
1000uF filter caps thinking that they weren't working properly. Oh
well, now they'll definitely be good for some time to come.

As it happens, I found an open IC protector on the power/servo control
board. After carefully examining the rest of the board and looking for
any faults or shorts, I decided to cautiously jumper across the
protector and see what would happen. The turntable control panel came
to life, so I put a record on it. It would try to start and abort
playback just before the tone arm would touch down. Hmmm.

That had me stopped for a bit until I thought about the bright light I
was using to illuminate my work area. After turning it off, startup
and playback of a record worked fine. I played a few hours worth of
records with no ill effects. I definitely will replace the protector
in the near future.

Now all I have to do is find a not-too-unreasonably priced source for
the Rohm ICP-N10 circuit protector with small quantity availability.
Digi-Key has a minimum order of some 3,000 (!!) units and while there
are some on eBay, I really don't want to pay $5 shipping and gouging
for items that would fit in a #10 envelope with tons of room to spare.

I am thinking that 23 years (!!) of on/off cycles and current inrush
is what drove the little circuit protector to its breaking point.
There are two inrush current limiters leading up to each filter cap on
the power/servo board and my guess is that they ease the strain on the
circuit protector.

William
From: Mike WB2MEP on 7 Jun 2010 18:58
On Jun 7, 12:46 pm, "William R. Walsh" <wm_wa...(a)hotmail.com> wrote:
> Hi!
>
> > Not sure it was this model, but they had some problems
> > with 100uF 16 volt caps shorting on some of these and
> > causing the problem you describe. Might have also opened
> > an IC protector, IIRC.
>
> Well, I was barking up the wrong tree at first. I replaced the two 25V
> 1000uF filter caps thinking that they weren't working properly. Oh
> well, now they'll definitely be good for some time to come.
>
> As it happens, I found an open IC protector on the power/servo control
> board. After carefully examining the rest of the board and looking for
> any faults or shorts, I decided to cautiously jumper across the
> protector and see what would happen. The turntable control panel came
> to life, so I put a record on it. It would try to start and abort
> playback just before the tone arm would touch down. Hmmm.
>
> That had me stopped for a bit until I thought about the bright light I
> was using to illuminate my work area. After turning it off, startup
> and playback of a record worked fine. I played a few hours worth of
> records with no ill effects. I definitely will replace the protector
> in the near future.
>
> Now all I have to do is find a not-too-unreasonably priced source for
> the Rohm ICP-N10 circuit protector with small quantity availability.
> Digi-Key has a minimum order of some 3,000 (!!) units and while there
> are some on eBay, I really don't want to pay $5 shipping and gouging
> for items that would fit in a #10 envelope with tons of room to spare.
>
> I am thinking that 23 years (!!) of on/off cycles and current inrush
> is what drove the little circuit protector to its breaking point.
> There are two inrush current limiters leading up to each filter cap on
> the power/servo board and my guess is that they ease the strain on the
> circuit protector.
>
> William

Try a vendor that supplies repair parts. These things were widely
used in VCRs & TVs in the 80's. My 2006-07 MCM catalog shows them for
$0.59 ea., qty 1 - 9.
The catalog also lists the current rating as 0.4 amps, so you could
just wire in a regular fuse (although 0.4 A isn't a standard fuse
rating)
From: Mark Zacharias on 8 Jun 2010 22:25
"William R. Walsh" <wm_walsh(a)hotmail.com> wrote in message
news:928eba00-59c7-4573-a144-819f3e00c786(a)b35g2000yqi.googlegroups.com...
> Hi!
>
>> Not sure it was this model, but they had some problems
>> with 100uF 16 volt caps shorting on some of these and
>> causing the problem you describe. Might have also opened
>> an IC protector, IIRC.
>
> Well, I was barking up the wrong tree at first. I replaced the two 25V
> 1000uF filter caps thinking that they weren't working properly. Oh
> well, now they'll definitely be good for some time to come.
>
> As it happens, I found an open IC protector on the power/servo control
> board. After carefully examining the rest of the board and looking for
> any faults or shorts, I decided to cautiously jumper across the
> protector and see what would happen. The turntable control panel came
> to life, so I put a record on it. It would try to start and abort
> playback just before the tone arm would touch down. Hmmm.
>
> That had me stopped for a bit until I thought about the bright light I
> was using to illuminate my work area. After turning it off, startup
> and playback of a record worked fine. I played a few hours worth of
> records with no ill effects. I definitely will replace the protector
> in the near future.
>
> Now all I have to do is find a not-too-unreasonably priced source for
> the Rohm ICP-N10 circuit protector with small quantity availability.
> Digi-Key has a minimum order of some 3,000 (!!) units and while there
> are some on eBay, I really don't want to pay $5 shipping and gouging
> for items that would fit in a #10 envelope with tons of room to spare.
>
> I am thinking that 23 years (!!) of on/off cycles and current inrush
> is what drove the little circuit protector to its breaking point.
> There are two inrush current limiters leading up to each filter cap on
> the power/servo board and my guess is that they ease the strain on the
> circuit protector.
>
> William


Nah, one of those 100uF caps is just intermittent that's all. Seen it
before. You'll just need to catch it in a shorted mode.

Mark Z.

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