Dual CS505-1

to keyboard and composed:



How does the pitch control work? Just curious.



- Franc Zabkar

**The pitch control for the 505 is an expanding pulley. Quite nifty. The
pulley comprises of a bunch of 'fingers' with a dome, which is pushed up
through the centre, thus expanding or contracting the diameter of the
pulley. It is barely possible that there is enough range in the adjustment
to cope with 50Hz, but I doubt it. It is possible that 50Hz pulleys may
still be available. The 505 is worth fixing, unless it has massive problems,
since it is an excellent turntable.

On Wed, 30 Aug 2006 12:18:21 +1000, "Trevor Wilson"
composed:



The specs allow only +/- 6%.



Would it make sense to machine your own fixed pulley and dispense with
the pitch control?



- Franc Zabkar

**Possible, but difficult. It would make more sense to do one of the
following, IMO:

* Locate an original 50Hz pulley.
* Find cheap, small power amp, feed it with a stable 60Hz sine wave into a
reverse connected power transformer. No need to adjust for 240 VAC and no
need to adjust for 50Hz. Power requirements for the 505 is probably less
than 10VA.

Can't source this so far.  Found scrap TTs on eBay, but that rather defeats
the object, since this is already a "scrap" TT!



Trevor, spookily I thought about that yesterday.  I understand that sync
motors don't like anything other than a nice sinusoidal input, so a
conventional inverter is out.

The label on the back of the TT says 110v at 50mA so only 5.5VA required.
With a linear amp a 10W design might just do it.  I have an old Mullard one
with Germanium transistors that is rated at 10W so will try that first.

Thought about 3 types of 60Hz sources;

- xtal controlled with divider then low pass filter;
- xtal controlled with divider then counter and simple DAC to generate
stepped sine wave;
- free running analogue oscillator using and op amp.

I am inclined towards the last option.  It's simple and there's no nasty
edges to get rid of.

Nick

**At least it would be a cheap and easy experiment. Personally, I would look
for something a little more (ahem) robust than an old Germanium amp, though.
Still, if you don't mind sacrificing it......

Hi Trevor,
would it be feasible to place a resistance in series with the motor to
achieve the design current flow through the motor? Is there any nasties to
be aware of with respect to doing this that would make it a no-no? I ask
because I also have a 110-120v turntable motor (Fujiya Audio IM-275-12B,
50Hz 110v 1500rpm 7.5w) that I purchased with the view to using off 240v
50Hz.
Best Regards.

**That should work. I've done it a few times, quite successfully. Measure
the resistance of the motor and choose a resistor of the same value or
slightly larger (TT motors should work fine with reduced Voltage, down to as
little as 50% supply). Be careful with resistor choice and location, since
it will have mains Voltage on it. If you want to get really tricky, you can
use a capacitor. Make sure the cap is a mains rated type!

Thanks Trevor, I shall experiment one day and see what I can come up with.

**Probably by connecting the windings in series, but I am not certain about
that.



**Very likely, yes.

  I suspect the answer to

If the windinga are parallel connected now, you'll be be able to connect
them in series.



yeah, the "pulley bit" on the end of the shaft will have to be replaced with
one that's 20% larger, these may ba available as a spare part or you may
have to get one made (someone with a lathe, maybe a mechanical engineer)



otoh maybe you could just hook both motors up in series :)

Bye.
   Jasen

Thanks to all who posted to this thread.

I now have the wiring details for 230v but am unable to source a 50Hz
pulley.

Building a 60Hz synchronous PSU for it.

Nick