I have a nice, otherwise well working Beomaster 900K. Every now and then, usually after extended play, it decides to mute itself. Lights stay on (so not a problem in the power switch), but nothing comes out of the speakers. If I turn it off and straight back on, it always continues to work as if nothing happened, so it doesn't sound like a bad contact or overheating, but rather an internal problem in some semiconductor perhaps...?

This happens seldom enough to not be a big nuisance, but I would spend some time trying to fix it if I had the faintest idea of where to start. Oh yes, this is always when listening to the radio, I don't have any other sources connected.

Try tapping the AF transistors gently with f.e. the handle of a screwdriver
next time it mutes.

Martin

Thanks. The problem may take days to surface, so this will have to wait until winter when I bring it home from the summer house and can keep its guts permanently on display

So you support my theory of some transistor shorting internally? I have two more 900's so I could of course try to swap stereo decoder boards to further isolate the problem... the problem must be before it or in it as both channels go silent.

Yes, most likely one of the IF transistors.
Of course, there could be many other reasons but that would be my first try.

Martin

Hi Mika/Martin,

I have exactly the same thing that happened to an immaculate BM4000.

Turn it on, tune a station -perfect, then after a while... click, nothing!

Reboot, try again, plays fine for a while then... click again.

I never got in to look around, but was leaning towards the IF FM tuning. I would be very interested to hear how you get along with this. In the meantime (when I get a chance) I will open it up and try the tap trick!

On another note, pardon my ignorance... but is there a proper technical term for (let me try to decribe it)... Say you're tuned into an FM station, and particularly with some treble dialed in, you get a faint background variable whining... almost sounds like frequency tuning? It does not exist on any other sources. Some sort of interference between the tuner/power supply?

edit: Heterodyne whistle?

Thanks in advance,

The BM4400 does not have AF transistors so is not prone to
this type of failure.
It will have to be something else. A cracked solder joint, a heavy tuning
drift outside of the AFC reach or some muting fault.

Yes, that's the whistle.

Martin

Dillen:

The BM4400 does not have AF transistors so is not prone to
this type of failure.
It will have to be something else. A cracked solder joint, a heavy tuning
drift outside of the AFC reach or some muting fault.

ARGH!

Sorry for the red herring Mika! ...and I was all fired up to go tap-tap tonight!

I guess at this point, I'll lean toward a cracked solder and have a look around when I have a chance... I'll put it on the "back burner" until then, as I was hoping it might have helped Mika and myself at the same time.

Dillen:

Yes, that's the whistle.

Ah! Thanks for the confirmation, Martin!

No problem Jeff - you need to get something older so you can tap as well