4000 Automatic Stereo 11 Sonorama export

OmerS · 4. Februar 2020, 07:37

One of the most difficult radios I have restored in my collection!

After removing and replacing ALL defective components on this radio, i was only able to receive AM (or MW) on one speaker..MONO (on the switch)

To receive "stereo" on this console, you have to press FM (or FM )) and STEREO

The schematics are VERY complicated and not complete, if one has it adapted to use a multiplex unit

In my case, I had a solid state unit made for me by someone, specificalyy for this unit

Here is the schematic of the original FM decoder and adaptation instructions

Does anyone have experience with this model, and know if this is how this receiver is supposed to work?

Does any one know the proper wiring for the multiplex?

Klarzeichner · 5. Februar 2020, 19:58

Omer,
your set ist a model of season 1961/62, indicated by the "11", while your wiring diagram refers to Freiburg 12 (Freiburg is the German model name) , where the "12" indicates the model of the 1962/63 season. I believe these two are identical, but not quite sure.

Assuming the "11" and "12" make no difference, wiring the multiplex socket should not make any trouble when working according to drawing. Comparing with the schematics, which you possess (in your link) will not be wrong to make sure to avoid mistakes.

You may use any mutliplex decoder, even newer ones. I added decoders featuring "modern" integrated circuits to Freiburg models like these without problems.

Make sure to connect the pins of your mpx socket...:
Pin 1 to decoder left channel output
Pin 7 to decoder right channel output
Pin 3 zo decoder MPX Input
Pin 2 to decoder ground
Pin 4 delivers a high rail voltage which can be limited by a resistor to a suitable voltage. If dc input current of a modern decoder is too high, you have to use a separate dc supply.
Your MPX Decoder should provide a 50 or 75 µs deemphasis (according to your country) in AF outputs.

Don't hesitate to ask for further details

Regards, Stefan

OmerS · 6. Februar 2020, 08:33

Here is the 9 pin version of the stereo decoder that I am using

I should note that the console ONLY plays on the left channel when it is in the AM (MW) mode?mono (NOT stereo)

Vacuum tubes, EF86 and EBC91 are both very weak on the right channel

Is this console /radio supposed to play on BOTH left and right speakers when engaged in AM?

Thank you for responding to my question and sharing your knowledge of the complexity of this great radio!

Omer

Klarzeichner · 7. Februar 2020, 15:04

First, your mpx decoder should be suitable - but it has a 9-pin plus while the console has a 7-pin socket. So the plug must be changed. The 9 pin one is for younger Sabas bearing the numbers 14 and 15.

"Is this console /radio supposed to play on BOTH left and right speakers when engaged in AM?"
Definitely yes, under all circumstances. If ot doesn't, there is a failure in switching devices.

Regards Stefan

OmerS · 7. Februar 2020, 22:21

All switches function properly The EBC91 tube is weak for the portion that is dedicated for mono/AM. Is there a possibilty that there is an issue with the audio transformer too?

The decoder that I am using, is a 7 pin made version of the schematic that was presented

thanks Omer

Klarzeichner · 8. Februar 2020, 11:24

Hey Omer,
the EBC 91 is in operation all the time, not only in mono, not only with AM. It has to be okay, so replace it when faulty. See my answer in the other thread.

"The decoder that I am using, is a 7 pin made version" - Fine!

BR Stefan

OmerS · 21. Juni 2020, 05:51

After tenuous work on this radio, and looking at a place one would never consider, the switch ( hiding on the side of the record player)for speaker combinations was partially disintigrated and not connecting to all combinations on one chanel

I removed this speaker switch from its location and rebuilt it with pieces of PC board and sheet metal cut to size The slider switch is operational again and the radio now functions in all modes

I hooked up the original decoder for the SABA 4000, and the radio now functions better ( the dial lights are not as bright, and the relay coordinates with the mono setting for AM)

Thank you very much for your assistance, and sorry for my delayed and extended response

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