grundig: 4070U/Stereo;

I have just obtained a Grundig radio -  4070M Stereo, serial no. 135975714 - so I`m hoping that because it is German, someone will be able to tell me where I can get a routeing diagram for the tuning cord, which is ultra complicated, and in this case the tuning capacitor has completely seized up, and I am in the process of dismantling it. A spring is also jammed inside the gear mechanism of the capacitor, and I cannot see where it has come from.

If I could get a service manual in English, it would help greatly; if not some diagrams from the German manual might help.

regards

graham guy

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Hi Graham,

most probably the model Grundig Konzertgerät 4070M Stereo is the right one you've looking for. Schematic and dial cord routing are available there.

The problem with your tuning capacitor could be caused by resinous grease in the tuning shaft bearing. Please add a picture here (max. 580 dpi width/ 40 kB file) which shows the tuning capacitor in detail.

Bernhard Nagel

(An Moderator: Beitrag zum obigen Modell verschieben, danke.)
Beitrag zum richtigen Modell verschoben. Wolfgang Bauer

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Hello, 

you have: 4070M Stereo, serial no. 135975714

please  see here the german model.

knoll

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Thanks Bernard/Knoll - You were correct about the capacitor bearing, which I have now removed, freed up, and refitted.

I am left with this capacitor spring which must be required to assist with the clockwise turning of the capacitor, as I can only get it to move anti-clockwise.

The FM tuning cap. is the opposite, it will only move clockwise, so I am stripping the FM tuner at the moment.

I have never seen such a complex tuning system; I believe the basic fault is in the clutch mechanism, but as I have just lost the cord ONCE AGAIN, I need the cord routeing before I can remove and check the clutch.

I would really like to get this radio working because looking at the components, it should be good quality.

rgds

graham

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Bernard - Good Afternoon - I now have the radio partially working - one channel only. Could you tell me what this black & white indicator is, and how a "decoder" is fitted, and does the stereo only function if a decoder is fitted - this could explain the one channel only working, but the stereo/mono switch is not very good so I am repairing it.

Thanks in advance for any info.

rgds

graham

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Graham,

to receive FM stereophonic transmissions, an ext. decoder (also called multiplex adapter) is necessary. The pictured part of the back cover indicates the 9 pole (Noval) socket where the Decoder 4 or Automatic Decoder 5 can be plugged in. The decoder itself can be mounted at the back plate.

The only difference between both units is the automatic switching stage at Decoder 5 with a relais, when a stereo station comes in. The black/white indicator indicates the presence of a stereophonic station (a moving coil turns 90° when the detected and rectified 19 kHz pilot tone is present).

They will be offered sometimes at ebay.de for moderate prices. Please take care not buying a Decoder 6, since this unit has a 10 pin plug! Decoder 6 has two valves.

The manual mono-stereo switch "overrides" the automatic switching function and connect both af channels when in mono pos.

To check both af channels, it makes sense of feeding a signal to the DIN pickup input. Both outputs should work equally. If not, compare the valve voltages from the ECC83 and ELL80. A common fault is situated into the DIN loudspeaker terminals. Since they contain a switch which disconnect the internal speaker when a plug is inserted, check the spring loaded contacts into the sockets.

The cord stringing diagrams you will find where the schematics are located: Go to the Pull-down Administration (at the model page), then click at "All schematics". This opens a pop-up, choose there the 4th pos. ...seil.pdf.

Hope, these infos will help.

Regards, Bernhard

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