Dampfradioforum

dear friends,I have a AEG bimby radio and I am repairing it now.I replacemend electrolitic capacitors(C50 andC51) and C48(0,1MF).The radio is playing perfect but there is a noise DINNNNN on the speaker when it is on the low volum.aeg bimby has same circuit with telefunken jubilate7.

Hello inecik!
You must replace C41,C45;C47.
They are often damged ( critical resistance) and may kill many parts.
As they are Output Transformer,Valve EL84,Rectifier,Mains Transformer.
GL
Claus

_________________
Wer mit der Röhre hört,der hört,wie es richtig röhrt :D

Is it a humming noise? There could be various reasons for that.

It is highly recommended to replace C48 (0.01µF) because it is usually leaky. This causes an excessive bias current of the EL84 tube. And also C47 (0.0047µF), which causes excessive power consumption if leaky. The latter has to be replaced by a DC 630 V or 1000 V type. Both capacitors may cause humming noise eventually when faulty.

If C41 is leaky, this causes no risk of damage to other components and no humming, but the tone control acts then as a volume control.

Make sure that the replacement capacitors C50 and C51 are connected to the chassis at the same point(s) where the original capacitors were connected, and that the connections are low resistive (e.g. clean).

Make sure that none of the winding teminals of the output transformer (Tr1) are interchanged. The primary winding is part of the humming compensation, which can only work properly if connected correctly. The secondary winding is not only for the speaker, but also for the negative feedback which can not work properly if the secondary winding is reversed.

If replacing the rectifier by a silicon rectifier, you have to add a resistor (approx. 100 Ohms / 2 Watts) in series with one of the rectifier terminals.

You may try to remove the EABC80 tube. If the humming noise then disappears, the fault is in the environment of the EABC 80, in this case you may try a new one. If the humming persists, the fault is in the environment of the EL 84 or in the power supply.

Good luck!

Lutz

I replacemend C48 but it is 0.1MF,for me there is no problem on C50 and C51.I will look windings of TR1.I didn't replacemend rectifier .I removed EABC80 tube and The noise is very low.

What happens if you connect Pin 8 of the EABC 80 to ground? If the humming then persists, it is likely that the EABC 80 is faulty.

Lutz

dear friends,I replacemend C41,C45,C47(4700pf 1600volt) and EL84 cathode bypass capacitor.now the noise very low,I can not replacement C44 because it has 3 leg,I didn't understand what is it.
EL84 voltage measurements:
pin2:zero voltage
pin3:6 voltage
pin7:232 voltage

C44 is a capacitor with shielding. If replacing it with a standard capacitor, you can replace the shield by a wire wrapped a few times around the capacitor and connected to ground. But in general, there is no need to replace that capacitor.

The voltages are ok. I think, you can enjoy your radio as from now.

Lutz

hello,I am not happy because my radio is perfect but there is a noise on the speaker still.I replecamend C40,C41,C45,C46,C47,C48,C50,C51.I checked the rectifier,I measuremend voltages on the EL84,and output trafo's windings.for me ,there are two tape recorder socket on my radio but there is a socket on radiomuseum and schaltplan.I don't anderstand that, is this a problem??? I can't add the pictures,I will try again

If the niose is very low, it may be normal. Hard to say from here.

The socket marked with a "Q" is for connecting a pick-up. It may also be used for connecting a tape recorder (playback only), or a CD-Player, MP3-Player or the like.

If there is a socket marked with a symbol like O_O, it is for a tape recorder (usually record and playback).

If there is a socket with a loudspeaker symbol, it is for connecting an external speaker which is operated simultaneously with the internal speaker. It may also be used for connecting a tape recorder (record only).

Lutz

the pictures

The upper socket is the one for the pick-up I described above.

The lower socket is for a tape recorder (record and playback). It may also be used for connecting a CD-Player, MP3-Player or the like. It was probably added some day, so that older radios don't have this socket while later radios have.

Lutz