Vintage Products

Re: Beomaster 4400 problems

tournedos — Fri, 10 Oct 2008 15:13:28 GMT

Tonight, I started to adjust the signal levels of the inputs. All was fine until I got to Tape 2 - the sound kept coming and going by itself. I cleaned the trimmers, no effect, I re-cleaned the switches, no effect. And tweaking and wiggling anything didn't have any audible effect. Silence, two or three seconds of music, silence, start over.

This was getting funky so I rigged up the oscilloscope. The signal went on uninterrupted on the connector from the DIN-preamp board to the switch panel. Looking at the schematic, I could see no other possible cause for this than the Tape 1/2 switches. I started to re-re-clean them with contact spray and physical exercise. While wiggling the switches, I happened to let the AFC ST key up. Music! Tape 2 plays fine unless I depress the AFC key, then it starts coming and going.

Why on earth would the FM muting function keep muting Tape 2, and only Tape 2?

Re: Beomaster 4400 problems

tournedos — Mon, 29 Sep 2008 14:12:12 GMT

The Beomaster now has two brand new good quality cermet trimmers controlling the idle current. It doesn't get a bit warm at the volumes I can use at this time of the day without disturbing the neighbours... I go on with mechanical cleaning now, and in the morning l I'll hook up the Pentas for a real test drive

Re: Beomaster 4400 problems

lausvi — Fri, 26 Sep 2008 00:30:52 GMT

tournedos:
This is a cool looking machine in the inside! This time I'll try to remember my principal decision to take some pictures each and every time I open a piece of B&O kit. Don't know about you people, but I never get tired of looking at those

Many B&O machines look very cool (also) in the inside! And one thing I enjoy about opening those is the smell that is inside those. Many B&Os that I have opened have had exactly the same smell inside and that's really a nice one and makes me smile everytime. Air from the B&O factory perhaps......

The pots that control the idle current are really prone to fail. I have seen many pots that have turned whole black by dust and most of them won't work: just break down. Better to replace those anyway. They might look good after some contact cleaner but in my experience they will be very unreliable still.

Re: Beomaster 4400 problems

tournedos — Thu, 25 Sep 2008 16:20:27 GMT

I finally had the energy to open up the Beomaster. Sure enough, the idle current trimpot of the offending channel is shot - it doesn't even feel right mechanically! Voltage over the emitter resistors was 90 mV vs. the 10-15 specified in the service manual, so I turned it off and will not use it before I have replaced the trimpots.

Also, the fork of the bass slider (or the actual pot, I didn't dig deep enough to be able to compare with the others) really was broken and doesn't reach the target. This will be repairable with some epoxy and creativity.

This is a cool looking machine in the inside! This time I'll try to remember my principal decision to take some pictures each and every time I open a piece of B&O kit. Don't know about you people, but I never get tired of looking at those

Edit: nothing was broken at the bass slider after all! The pot had just slipped out of its place. They are held in place with some kind of funky clips and it may have actually moved during transportation.

Re: Beomaster 4400 problems

Jandyt — Wed, 24 Sep 2008 13:16:13 GMT

3. It needs to be like this so you can record off FM etc.

Re: Beomaster 4400 problems

Dillen — Wed, 24 Sep 2008 13:03:14 GMT

1, Definitely ! Replace and readjust. Do both channels - one at a time.

2, Probably - or it has lost its tiny coal tip. Take apart and repair.

3, B-test (after-tape monitoring) function. It's supposed to be like this as you've already found out yourself.

Martin

Beomaster 4400 problems

tournedos — Wed, 24 Sep 2008 04:19:07 GMT

My new Beomaster 4400 has some minor problems. I'll open it later today, but as always, I thought I'd ask first...

First and worst, the other cooling fin on the right gets real hot. I suppose this is the output amp idle current being badly off, since I hear nothing wrong with the sound? Are the trimpots prone to go bad?

Secondly, the bass control doesn't work. I suppose the fork of the slider is broken...

And last, the Tape 1 selector doesn't reset the others, i.e I have to turn the receiver off first before going for example from FM to tape 1, otherwise both selectors stay down. Some common mechanical problem perhaps?

Edit: I did the unthinkable and read the user manual. Seems the last "problem" is by design