Hi everyone,

I had a repair shop fit a capacitor and lamp kit to my Beomaster 1900 as provided by Martin - the unit had the humming issue. I got the unit back and it sounded wonderful but I encountered the following issue (I cannot verify if this existed before the repair or not as I got the unit second hand it was humming so badly I had to send it away).

I turn on the beomaster and work my way through each of the FM channels programming them for stations around my area.

Once I get to FM5, I can manually tune FM5 with the large tuning wheel without any issue.

The problem is that once the FM5 dial is moved, it disturbs the FM settings for the other presets.

If I am listening to FM2 and move the tuning wheel for FM5, it is possible for that action to take FM2 off the channel for which it was programmed.

It seems when FM5 is in the lower end of the frequency range then all other presets function as desired but once FM5 is moved into the upper range then it disturbs all the other presets.

The repair tech is not a B&O expect but has managed to replace all bulbs and caps with the service manual I provided him. Once receiving the unit back he has also checked all the tuning voltages and adjusted them correctly yet still this problem remains. I have a donor unit which has some other damage, we have tried swapping the tuners but this didnt resolve the issue.

He has asked me to jump on here to see if I can get any suggestions.

Any assistance would be greatly appreciated.

Thanks

Andrew

Have to admit up front that I've never worked with these personally... But I took a look in the schematic, and I'd check the diodes D1 to D5 inside the preset module - looks like a leaking D5 could cause preset 5 to disturb the others. Those are a penny a piece 1N4148's so it will not be an expensive experiment to just replace them.

This might sound a bit odd, but I never thought this was a 'problem'.

Both my 1900 and my 2000 did exactly the same thing. If you switched to FM5, changed the tuning and then switched to FM1-4 the stations were gone. But the solution was quite easy: Switch it off and on again and the stations are back.

I believe this is somehow caused by the AFC...

thanks Ablaumeise... 

the issue I had was that when listening to FM3 (ie the input is set to FM3), moving the FM5 dial will re-tune FM3, its almost as if there is a solder track jumped in the set, the repair tech has been looking at it and I expect to get the set back tomorrow, I will advise everyone of the outcome.

Andrew

Could be something simple, like a cracked solder joint at the tonecontrol/FM-presets board connectors.
A missing ground connection could easily mess things up. A broken copper track maybe. Worth checking.

Also worth checking if something high on the mainboard is touching the presets board when it is mounted.
Holding slots are provided in the plastic chassis to allow the presets board to be held vertically while servicing.

Martin

Andrew:

the issue I had was that when listening to FM3 (ie the input is set to FM3), moving the FM5 dial will re-tune FM3, its almost as if there is a solder track jumped in the set, the repair tech has been looking at it and I expect to get the set back tomorrow, I will advise everyone of the outcome.

Apparently I didn't completely understand what you meant - in my case it only happened if you switched from a tuned station to another station, changed the tuning of this station and switched back to the first one.

In this case I would also suggest searching for bad solder joints or something similar...