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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 12th Oct 2018, 5:02 pm   #21
roffe
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Default Re: Reviving Radio in old German Radiogram

Agree with ms660. It has to be a Stern radio Weimar 4680 in a radiogram cabinet.

I even googled the number on the loudspeaker and it turned out to be a Stern loudspeaker. Furthermore-look at the fasteners that hold the loudspeaker and compare these and also the radio chassis as a whole with this link:-

https://sprzedajemy.pl/stare-radio-w...299-nr41957412

That 'knob' on the sliding door is also a typical Stern.

The original is a Blaupunkt Arkansas.
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Old 3rd Nov 2018, 7:57 pm   #22
beachboybuff
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Default Re: Reviving Radio in old German Radiogram

Hello All,

Thank you for all of your help and advice. I have been busy recently so not had too much spare time to look at Radiogram, but I am still keen to get it working properly. I have removed the cartridge from the radiogram, and this has had no effect on the feedback. I tried touching the wires that the cartridge attaches to when the radiogram was on, and there was no buzzing or static noise at all, which I expected there to be, which suggests to me that it is a problem of some description with the record playing part of the circuitry inside the radiogram. Does anyone have any ideas of things it might be, or things to check from these symptoms?

Regards,

Michael
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Old 5th Nov 2018, 6:17 pm   #23
Edward Huggins
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Default Re: Reviving Radio in old German Radiogram

This suggests the amplifier section is faulty and is likely to mean you will get no sounds from the Tuner section either. Try a contact cleaner on the piano keys and actuate them.
If no joy, you will need to signal trace the circuit. Best starting with the amplifier section first. But before you do this, we need to know what confidence/experience you have to work on the circuitry within the chassis of this, especially when it's powered up?
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Old 7th Nov 2018, 8:10 pm   #24
beachboybuff
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Default Re: Reviving Radio in old German Radiogram

Hello Edward,

By Tuner section, do you mean the Radio output, as this appears to be working faultlessly. Problems only start when radiogram is switched to the phono input. I don't have a whole lot of experience with working on this sort of thing, although I'm no stranger to wiring plugs, soldering, etc. I like to think that I would be fine working on circuitry when powered up, and that I won't do anything daft.

Regards,

Michael
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Old 8th Nov 2018, 11:37 am   #25
Edward Huggins
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Default Re: Reviving Radio in old German Radiogram

Ah I see, so the Radio (Tuner) does function well and you now say you are getting a good output via both the amplifiers? Then the fault may well be in the switching that selects the phono/gram input or faulty connections back to the pick up cartridge. Again, I suggest you signal trace starting at the pick up cartridge connecting pins, then working backwards to the phono switching. At this stage we have not yet established if the cartridge is still working.
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Old 8th Nov 2018, 6:57 pm   #26
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Default Re: Reviving Radio in old German Radiogram

Just checking - the replacement cartridge is a ceramic pickup, not a magnetic one? Magnetic cartridges wont work at all as they only put out a few mV of signal instead of volts.

Kevin.
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Old 9th Nov 2018, 2:09 pm   #27
beachboybuff
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Default Re: Reviving Radio in old German Radiogram

I had suspected that it is not a cartridge issue, as there is no change in symptoms when cartridge is on or off. There is no audible feedback when touching the bare wires that the cartridge would connect to when switched to phono input, which I would have thought there would be (possibly wrongly). Edward, I will look into signal tracing as you have suggested, although I do not yet have a signal generator/tracer.
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Old 9th Nov 2018, 3:28 pm   #28
brightsparkey
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Default Re: Reviving Radio in old German Radiogram

On my Dual changer, at least, the cartridge is only connected once the needle is down, to prevent a bump when it lands being heard. Don't know if this is common. It maybe you have to lower the needle towards the platter before its put in circuit.

Kevin.
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Old 9th Nov 2018, 5:21 pm   #29
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Default Re: Reviving Radio in old German Radiogram

If the problem is narrowed down to the receiver and cleaning the switch contacts doesn't sort it out do a hum injection test with a meter probe, the gram input on the schematic in the link that was posted is socket III, socket II is ground and socket I is the radio signal output for a tape recorder etc. The switch contacts in the circuit and the switch layout drawing are shown with the receiver switched to the Off (Aus) position, the switch layout drawing is as viewed from above, both MW and LW buttons have to be engaged for the gram input to be selected.

As an aid (if needed) here's the signal flow path from the gram socket in the schematic through the switch contacts (numbers given) when the gram function is selected:

Socket III >> switch contacts 64--65>>switch contacts 49--50>>switch contacts 18--17.

Lawrence.
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Old 12th Nov 2018, 11:30 pm   #30
beachboybuff
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Default Re: Reviving Radio in old German Radiogram

Thank you for your help everyone. I have arranged to borrow some equipment soon, and will carry out signal tracing and switch cleaning and report back after that.

Kevin, I did try lowering the arm down, but nothing appears to happen any different. I can't see any mechanism that would detect when the arm was up or down either.

Thanks again,

Michael
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Old 27th Dec 2018, 3:51 pm   #31
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Default Re: Reviving Radio in old German Radiogram

Hello all and Merry Christmas

Sorry it's been a awhile since I last posted on this thread. My friend who agreed to lend a signal trace hasn't been down in this part of the country recently, so I bought a newer multi meter that has a continuity test feature, just to check that there were no breaks in the circuit. This lead me to discover that the turntable is in no way connected to the amp, other that the leads which drive the motor. I took the turntable out of the radiogram and turned it over to see what was going on, and it looks as if a previous owner has deliberately disconnected it for some reason. The two wires which attach to the mono cartridge go into four wires, two of which are connected to a wire which has been simply cut part way along, and the other two are connected to nothing. I have taken a picture of the terminal to which the four wires go. It beats me why someone would just cut wires and disconnect the turntable like that?

I think I am going to have a look at a diagram for the record deck, (a BSR UA14 I think), and see what the wiring looks like for that.
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Old 27th Dec 2018, 4:20 pm   #32
Michael Maurice
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Default Re: Reviving Radio in old German Radiogram

That looks like it was originally a mono cartridge. That brown cable goes to an amplifier probably via a 3 pin or 5pin DIN plug. Make sure its plugged in correctly.
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Old 27th Dec 2018, 6:25 pm   #33
beachboybuff
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Default Re: Reviving Radio in old German Radiogram

Yes, I think you are right, it was a mono cartridge originally as I found an old mono BSR cartridge in the bottom of the radiogram. The brown wire I think should go to the amplifier, but it has been cut, and the problem is I can't seem to find where it was originally plugged into? I have searched high and low to look for the other end of the cable, o where it may have coe from, but cannot seem to find where it goes into. The only sockets on the rear of the radiogram are for a tape recorder and an external loudspeaker.
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Old 27th Dec 2018, 6:50 pm   #34
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Default Re: Reviving Radio in old German Radiogram

The socket on the rear in the radio only version in the link I posted has inputs for tape and gramophone pickup, a picture of the outside of the back cover showing where the socket is might help.

Lawrence.
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Old 29th Dec 2018, 3:54 pm   #35
beachboybuff
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Default Re: Reviving Radio in old German Radiogram

Hi Lawrence,

Thank you for your reply. The radiogram appears to have sockets for a tape recorder input and a loudspeaker output. I have added some pictures as you have asked. I have taken the chassis out of the case and cannot find the other end of the cut turntable wire anywhere, so it is possible that the record player was connected thorough the tape input, and the plug was cut off, although why anyone would do this is beyond me.

Michael.
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Old 29th Dec 2018, 3:59 pm   #36
ms660
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Default Re: Reviving Radio in old German Radiogram

Quote:
Originally Posted by beachboybuff View Post
Hi Lawrence,

Thank you for your reply. The radiogram appears to have sockets for a tape recorder input and a loudspeaker output. I have added some pictures as you have asked. I have taken the chassis out of the case and cannot find the other end of the cut turntable wire anywhere, so it is possible that the record player was connected thorough the tape input, and the plug was cut off, although why anyone would do this is beyond me.

Michael.
That socket is for both tape and gramophone, see my earlier post (Post 29) for what pin numbers pertain to gramophone input.

Lawrence.
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Old 29th Dec 2018, 4:12 pm   #37
beachboybuff
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Default Re: Reviving Radio in old German Radiogram

Thank you very much indeed for your help Lawrence, you have probably saved me a fair amount of head scratching! Out of interest and for future reference, which part of the schematic that you posted were you looking at to find this out?

Thanks again for your time and assistance.

Michael
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Old 29th Dec 2018, 4:17 pm   #38
ms660
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Default Re: Reviving Radio in old German Radiogram

Quote:
Originally Posted by beachboybuff View Post
Out of interest and for future reference, which part of the schematic that you posted were you looking at to find this out?

Michael
The socket(s) marked 1, 11 & 111 below switch contacts 64, 65 & 66.

Lawrence.
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