Hi All,

As some of you are aware, I have an old Sony Midi system complete with turntables.

In recent years, the only thing Ive used the main boxy bit for, is to provide 12V to drive the turntable. Id like to feed it from something a bit more compact. But as usual, have zero budget.

Ive taken the bottom of the turntable and discovered
It has a 9 point Something volt motor (it also has an auto
Arm liftty and Putty away mechanism).

I checked the power out from the big box, and its a little over 12V. I had a dig in my PSU box and the nearest Ive got claims to be 13.1 V.

Does the team think thats near enough? Or do I need to get Id down? If so, could I get away with adding a diode (and resistor (value?)?) in series?

If not, could I add a 12V regulator? Or would I need more than 13V to feed the regulator?

TIA

Chris

On Tuesday, 16 April 2019 07:32:16 UTC+1, wrote:
Hi All,

As some of you are aware, I have an old Sony Midi system complete with turntables.

In recent years, the only thing Ive used the main boxy bit for, is to provide 12V to drive the turntable. Id like to feed it from something a bit more compact. But as usual, have zero budget.

Ive taken the bottom of the turntable and discovered
It has a 9 point Something volt motor (it also has an auto
Arm liftty and Putty away mechanism).

I checked the power out from the big box, and its a little over 12V. I had a dig in my PSU box and the nearest Ive got claims to be 13.1 V.

Does the team think thats near enough? Or do I need to get Id down? If so, could I get away with adding a diode (and resistor (value?)?) in series?

If not, could I add a 12V regulator? Or would I need more than 13V to feed the regulator?

TIA

Chris

A diode would do it.


NT

On 16/04/2019 07:32, wrote:

Hi All,

As some of you are aware, I have an old Sony Midi system complete with turntables.

In recent years, the only thing Ive used the main boxy bit for, is to provide 12V to drive the turntable. Id like to feed it from something a bit more compact. But as usual, have zero budget.

Ive taken the bottom of the turntable and discovered
It has a 9 point Something volt motor (it also has an auto
Arm liftty and Putty away mechanism).

I checked the power out from the big box, and its a little over 12V. I had a dig in my PSU box and the nearest Ive got claims to be 13.1 V.

Does the team think thats near enough? Or do I need to get Id down? If so, could I get away with adding a diode (and resistor (value?)?) in series?

If not, could I add a 12V regulator? Or would I need more than 13V to feed the regulator?

TIA

Chris



I'd *expect* it to be OK, but would be tempted to try to measure the
voltage from the original PSU on-load, and see if it's 12v then, and get
a PSU as close to that as possible, or use a higher PSU and a regulator.
Apparrently you'll need at least 14.5v to drive a typical 12v regulator
and *guarantee* 12v:

https://electronics.stackexchange.co...-input-voltage

I'd expect the motor drive to be regulated in the turntable, so I'd
expect the main problem is not burning that up :-)

The latter sounds feasible but you need to know the current drain when its
running under max load and of course you need to measure the voltage
supplied under max load too, it might not be a regulated supply. If you opt
for an external psu, put it as far away as you can to prevent any inductive
pick up, on the other hand by a turntable and donate the old working system
to somebody else.


Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
wrote in message
...

Hi All,

As some of you are aware, I have an old Sony Midi system complete with
turntables.

In recent years, the only thing I've used the main boxy bit for, is to
provide 12V to drive the turntable. I'd like to feed it from something a
bit more compact. But as usual, have zero budget.

I've taken the bottom of the turntable and discovered
It has a 9 point Something volt motor (it also has an auto
Arm liftty and Putty away mechanism).

I checked the power out from the big box, and it's a little over 12V. I had
a dig in my PSU box and the nearest I've got claims to be 13.1 V.

Does the team think that's near enough? Or do I need to get I'd down? If
so, could I get away with adding a diode (and resistor (value?)?) in series?

If not, could I add a 12V regulator? Or would I need more than 13V to feed
the regulator?

TIA

Chris

On 16/04/2019 07:32, wrote:

Hi All,

As some of you are aware, I have an old Sony Midi system complete
with turntables.

In recent years, the only thing Ive used the main boxy bit for, is
to provide 12V to drive the turntable. Id like to feed it from
something a bit more compact. But as usual, have zero budget.

Ive taken the bottom of the turntable and discovered It has a 9
point Something volt motor (it also has an auto Arm liftty and Putty
away mechanism).

I checked the power out from the big box, and its a little over 12V.
I had a dig in my PSU box and the nearest Ive got claims to be 13.1
V.

One silicon diode and one Shottky diode in series will drop a shade
under a volt which should be fine. It is unlikely that something that is
old and designed for a crude bridge rectifier PSU would be particularly
voltage sensitive. The PSU voltage of the original is quite likely to be
load dependant and higher when not spinning up the turntable.

The main thing you need to know is how much current does the turntable
draw at 12v.

Does the team think thats near enough? Or do I need to get Id down?
If so, could I get away with adding a diode (and resistor (value?)?)
in series?

If not, could I add a 12V regulator? Or would I need more than 13V to
feed the regulator?

Although low dropout regulators are available the most common ones need
a couple of volts headroom.

--
Regards,
Martin Brown

Hi All,

Thanks for the replys. I will try and get more info.

Someone spoke of it probably being regulated in the turntable.

There is no evidence of this.

The wires carrying 12.1 volts come in, go to a tiny PCB with no components on either side, and then goes off to
Power the motor (small round can with 9V written on it)
and also the arm twidly mechanism.

I do have an 8V PSU kicking about, maybe I should check what that appears to be putting out, and if its around the 9V mark, see what the turntable does with that.

Otherwise, I might go back to driving it with the big box.

Best regards

Chris

In article ,
wrote:
Hi All,

Thanks for the reply‘s. I will try and get more info.

Someone spoke of it probably being regulated in the turntable.

There is no evidence of this.

The wires carrying 12.1 volts come in, go to a tiny PCB with no
components on either side, and then goes off to Power the motor (small
round can with 9V written on it) and also the arm twidly mechanism.

I do have an 8V PSU kicking about, maybe I should check what that
appears to be putting out, and if it‘s around the 9V mark, see what the
turntable does with that.

Otherwise, I might go back to driving it with the big box.

Have you looked for a schematic of the amp online? Should show you the PS,
and perhaps test voltages, etc.

--
*I didn't say it was your fault, I said I was blaming you.

Dave Plowman London SW
To e-mail, change noise into sound.

On Tuesday, 16 April 2019 13:45:50 UTC+1, wrote:
Hi All,

Thanks for the replys. I will try and get more info.

Someone spoke of it probably being regulated in the turntable.

There is no evidence of this.

The wires carrying 12.1 volts come in, go to a tiny PCB with no components on either side, and then goes off to
Power the motor (small round can with 9V written on it)
and also the arm twidly mechanism.

I do have an 8V PSU kicking about, maybe I should check what that appears to be putting out, and if its around the 9V mark, see what the turntable does with that.

That probably would work.

NT

Otherwise, I might go back to driving it with the big box.

Best regards

Chris

On 16/04/2019 13:45, wrote:
Hi All,

Thanks for the replys. I will try and get more info.

Someone spoke of it probably being regulated in the turntable.

There is no evidence of this.

The wires carrying 12.1 volts come in, go to a tiny PCB with no components on either side, and then goes off to
Power the motor (small round can with 9V written on it)
and also the arm twidly mechanism.

I do have an 8V PSU kicking about, maybe I should check what that appears to be putting out, and if its around the 9V mark, see what the turntable does with that.

Otherwise, I might go back to driving it with the big box.


Is the motor AC or DC?

It's quite possibly AC, so the turntable speed is synchronised to the mains.

Andy

Hi All,

I measured the original supply voltage on load, and it was a shade under 12V (its a very lightweight turntable).

I had another dig in my spare PSU box and found a couple of 12V SMPUs. One of which measured 12.2V off load.

I decided to go for it.

The turntable played fine 11::^*)).

I dont think I checked the on load voltage, as I assumed it would be the same with such a negligible load.

I listened to about a track and a half of an LP, and none of the magic black smoke escaped.

Thanks for all the advice.

On Tuesday, 16 April 2019 22:45:49 UTC+1, wrote:
Hi All,

I measured the original supply voltage on load, and it was a shade under 12V (its a very lightweight turntable).

I had another dig in my spare PSU box and found a couple of 12V SMPUs. One of which measured 12.2V off load.

I decided to go for it.

The turntable played fine 11::^*)).

I dont think I checked the on load voltage, as I assumed it would be the same with such a negligible load.

I listened to about a track and a half of an LP, and none of the magic black smoke escaped.

Thanks for all the advice.

Good job. If you find a 9v wallwart change over to that, it'll avoid cooking the motor regulator.


NT

On Tuesday, 16 April 2019 21:16:48 UTC+1, Vir Campestris wrote:
On 16/04/2019 13:45, wrote:
Hi All,

Thanks for the replys. I will try and get more info.

Someone spoke of it probably being regulated in the turntable.

There is no evidence of this.

The wires carrying 12.1 volts come in, go to a tiny PCB with no components on either side, and then goes off to
Power the motor (small round can with 9V written on it)
and also the arm twidly mechanism.

I do have an 8V PSU kicking about, maybe I should check what that appears to be putting out, and if its around the 9V mark, see what the turntable does with that.

Otherwise, I might go back to driving it with the big box.


Is the motor AC or DC?

It's quite possibly AC, so the turntable speed is synchronised to the mains.

Andy

Mains TT motors use the mains frequency for control, low v ones are dc motors with a negative impedance speed regulator.


NT

On Tuesday, 16 April 2019 09:53:39 UTC+1, Martin Brown wrote:
On 16/04/2019 07:32, wrote:

I checked the power out from the big box, and its a little over 12V.
I had a dig in my PSU box and the nearest Ive got claims to be 13.1
V.

One silicon diode and one Shottky diode in series will drop a shade
under a volt which should be fine.

Silicon diodes drop 0.65v at very low current, 1-2v at full whack. A single si diode will be fine.


It is unlikely that something that is
old and designed for a crude bridge rectifier PSU would be particularly
voltage sensitive. The PSU voltage of the original is quite likely to be
load dependant and higher when not spinning up the turntable.

Ideally you want 9v, but it's been ok on 12.


The main thing you need to know is how much current does the turntable
draw at 12v.

an amp at most, but more when starting. A 3A diode should be ok.

Of course the 13.1v psu might deliver much more, if it's heavy especially. That would complicate things. Measure it.


NT

On Tuesday, 16 April 2019 07:32:16 UTC+1, wrote:
Hi All,

As some of you are aware, I have an old Sony Midi system complete with turntables.

In recent years, the only thing Ive used the main boxy bit for, is to provide 12V to drive the turntable. Id like to feed it from something a bit more compact. But as usual, have zero budget.

Ive taken the bottom of the turntable and discovered
It has a 9 point Something volt motor (it also has an auto
Arm liftty and Putty away mechanism).

I checked the power out from the big box, and its a little over 12V. I had a dig in my PSU box and the nearest Ive got claims to be 13.1 V.

You'd need to check those claims, is this AC or DC 13.1 seems an odd DC voltage to claim.


Does the team think thats near enough? Or do I need to get Id down? If so, could I get away with adding a diode (and resistor (value?)?) in series?

Well a diode can take it down by about 0.7V per diode (silicon)
that should be OK, but if it lowered too much the motor might slow down.


If not, could I add a 12V regulator? Or would I need more than 13V to feed the regulator?

Standard regulators need about 2 to 2.5V over the 12V and cost about 25P depending on supllier but the LDO regulators can work at about 0.5V over the 12V but they are normally over a £1 each


TIA

Chris

On Mon, 15 Apr 2019 23:32:13 -0700 (PDT)
wrote:

Hi All,

As some of you are aware, I have an old Sony Midi system complete
with turntables.

In recent years, the only thing Ive used the main boxy bit for, is
to provide 12V to drive the turntable. Id like to feed it from
something a bit more compact. But as usual, have zero budget.

For only very slightly more than zero budget you can get variable PSUs
and regulators like https://www.ebay.co.uk/itm/181961569850 or
https://www.ebay.co.uk/itm/332847087208 on eBay.

Obviously first check the drain of the existing supply, and having
obtained an appropriate regulator check its performance under load.