Phono-Super 9

Dear RMorg members, 

I am restoring a Saba Phono Super 9 radio and I have to replace the potentiometer of the bass tone control that of 3 + 3 MOhm Log that i never seen before, i do not know how it works and i did not found a description in the Web,  also in the electric schema it is represented with a different symbol (photo attached).

I have done a lot of research on the web to find a potentiometer like that, but unfortunately I have only found logarithmic potentiometers of at most 1MOhms or linear ones of 2.5 or 5 MOhm that I do not know if they can fit  anyway. 

If someone could advise me where to buy such potentiometer, even second hand, or could give me some suggestion to try to repair the existing one, or alternatively find a solution to get around the problem, I would be very grateful. 

Thank you in advance for the attention

Roberto 

Can you explain, what is the problem with the potentiometer?

Kazmer first of all thank you for your attention,

when I turn the knob counter clockwise (pls. refer to the picture)  until reaching the end of the stroke the sound is enough clear and strong, while when I rotate clockwise the sound weakens until it almost disappears and s at the end of the stroke it is very weak and distorted.

I checked the values of the resistors and capacitors connected to the potentiometer and they all look correct, pls. find the schema in the picture. 

I have also measured values of the resistence of the potentiometer and of the voltages that i reported in the attached picture, and franckly for me are not clear at all.

Thanks a lot

Roberto

It is unclear where the voltage originates.  The diagram you provide is both incomplete and hard to read.

I don't think there should be any direct voltage on this control, but I may be wrong.

Bob

Dear Bob,

many thanks for your doubts about the presence of voltage in the potentiometer. So I checked the circuit more carefully and I immediately discovered and replaced the faulty component and now it is all right: it is the capacitor shown in the image that is at a loss.

In any case I did not understand the values of the measuruments of resistence I did on the potentiometer that misled me.

Many thanks again for your precious contribution.

Roberto

Hi Foley....It is a beautiful set! I had a similiar problem with a 1940's set. I used a dimmer switch for a lamp.It cut down my voltage , and in effect slowed the turntable motor. It worked well! I mounted it inside cabinet. Give it a try...let me know.....AL

Alfred,

thanks for the hint and your approach to a solution.

In future though, please don't open a new thread when you want to reply to an existing one. In certain cases, subeditor rights are required to answer, hence the 'reply' function is disabled for those not having applied for subeditor (sorry i can't find the translation we used for the english language - but I'm sure you understand what I mean).

Alternatively, you can mail to the author and ask him to publish your response.

Regards
Mark

Hello all, this is my first post to the forum as I am a new member of radiomuseum.org.  My first question has to do with one of my new addtions, the SABA Phono-Super 9.  I just purchased this radio/phono from an individual in Germany in almost perfect condition.  The radio portion is working fine, but the phonograph is spinning to fast. Everything appears to be fine on the inside, so I think this may have something to do with the 50hz/60hz differences between the US and EU. 

I have tried to solve this problem and have asked a few people what they would do.  One person said to change the value of the capacitor on the turntable motor.  Another said the wiring from the turntable motor to the main power supply may need to be switched and another said that I may need a new spindle for the motor that would work here in the USA on 60hz.

The turntable is a Perpetuum-Ebner 4230 I believe. 

Someone told me that these PE turntables run at 168 volts, in between the EU and USA voltage and the wires running from the turntable motor to the main power supply may need to be switched.  Is this a 50hz motor?  If so, I can see why it is running fast here in the US where we use 60hz. Most turntables that were sold in Europe utilize 50 hz motors and when they are used in the US run about 20% faster than they should.  To solve this problem companies like Garrard and Thorens offered alternate motor spindles depending on where you were located and the power situation in that country.

Does anybody have any suggestions on how I can get this spinning slower so I can play my LP's at the right speed?  Any assistance would be greatly appreciated.  This is a great unit and I hope that there is a quick fix for this issue!

Thanks!

Foley

Edit 18-9-2018: Dead links to ebay removed

Hello Foley,

you are right it's a problem with the 50/60 Hz power supply. The motor is a synchronous motor type. That means it always runs with the speed of the AC power. The input voltage may vary in a wide range (10 or 20%) with no effect to the turns of the motor. For some PE chassis are differerent spindles available.

If you have a look at the schematics of the Saba Phono-Super, you will see that the turntable is a 220V type. If you change the voltage selector to 110V the transformer work like a auto-transformer for the turntable motor. The voltage will be nearly 220V.

Maybe to solve your problem you have to use a electronic transformer. In Europe we can buy DC/AC converters for cars. They convert 12VDC to 230VAC with 50Hz. The output is sin-wave or nearly sin-wave for the cheaper one.

Michael