1, Any good supplier will have dial string. It's a fiddly job but very rewarding. Lots of patience and coffee.

2, I have a used part in stock.

3, I don't know what this is but held up against 4, it seems that someone tried to lubricate and used the wrong agent.
Isopropanol (tapehead cleaner, carburettor alcohol or whatever you prefer to call it) will remove most, I'm sure.
If you need to lubricate anything, use silicone grease or sewing machine oil, never motoroil, "hobby oil" or WD40.

4, Probably a seized tuning capacitor, same as the above.

5, For those who stare at a Beomaster 901 and wondered where the headphone socket is - it's at the back !
This suggests that the connecting of a headphone is more or less permanently.
The headphone output is at speaker level so no problem in using normal 8 ohm headphones.
Having said that; There are two different Beomaster 901's, one type has two speaker outputs (1 pair), the other has 4 (2 pairs).
With headphones connected permanently, the potential load of the
amplifier will be too high if at the same time using 4 ohm speakers, one pair or maybe even 2 pairs.
If using 8 ohm speakers, I see no problem in using normal 8 ohm headphones.
If using 4 ohm speakers, the speakers will have to be disconnected
or the headphones will have to be of a higher impedance.
Since the Beomaster 901 has no speaker switches, using the latter was what B&O suggested.

Martin

The logic is fine !

Though I tend to lean more towards a theory of aging power supply caps. Do you have the hum also when only speakers are connected ?

Dial string is sold by the meter. There's really no good alternative to real dial string though I've heard some people have used fishing line. I haven't tried this myself so I really can't advice. I always use real dial string.
The string needs to have a certain amount of flexibility without actually stretching - hard to explain but you can feel
it when working with the string. 

Martin

Glad it was. I have been re-arranging my room for about 5 hours and there is a lot of stuff to move from one place to another... some radios, even more tape recorders and few computers....  :)

There is no hum or anything like that with speakers (or at least is not audible). And the problem was the same already with my earlier gotten Beocenter 1400 (which is the same as 
the 901 by the amplifier). Or it might be that they both would have aged caps to cause this but I wouldn't really think that to be the case). Also when in use with my Sennheiser wireless headphones there is no probelm at all (and I believe those have much higher impedance as they are wireless). I have tried only with the Form 1's. Somehow I got the
idea of the too low impedance... there is a text next to the headphone socket telling that the minimum is 100 ohms. And the Form 1's are rated... I think 47 ohms or something like that.

Some older non-B&O radio I have seen had a small spring in the string, but in this case it won't work as there is no straight line enough long to have the spring in the string... otherwise I could have used the original with a small spring added. But I know what you mean by the flexibility of the stuff.

The spring sits inside the nylon wheel at the potentiometer.

I normally use a pair of U70 for testing headphone outputs and never had any problems but they probably have an even higher impedance, I don't remember. Anyway, putting a series resistor in each channel won't hurt anything.

Martin

Dillen:

The spring sits inside the nylon wheel at the potentiometer.

 

Indeed, I almost forgot it. I'll get that fixed next time I take a look on that. I might have some other string that might do the trick (flexible enough) so I'll try them first. The difficult part will be getting it in but that will only need a bit of creativity, I guess. :)

Dillen:

 

I normally use a pair of U70 for testing headphone outputs and never had any problems but they probably have an even higher impedance, I don't remember. Anyway, putting a series resistor in each channel won't hurt anything.

 I checked this out to be sure: U70's are 140 ohms and Form 1's only 35 ! So it will make a difference indeed. Would a proper resistor be as small as 1/2 watts and -should we say- 100 ohms to get over the requested rate of 100 ohms? Should I have one resistor per channel or just one in the negative wire? As my original idea was to make the extension cord (because the placement of the connector!) so I could add the resistor inside the plug.

 

 

 

Putting 100 ohms in the leads will probably take the level down enough to make it practically useless but the ohmic value would be
correct for the impedance and trying won't hurt anything.
A resistor of 1/2 Watt could get hot but try with low volume first and feel your way.
The correct way would be to use two resistors - one for each channel
in the respective positive wires.

The best thing would probably be to try to locate a pair of U70 or similar higher impedance headphones.

Martin