ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I'm working on my 3rd (and final) Beomaster 4000 project and only get pure static on the FM section of things. Checked all the voltages on the board and around TR10 and things look good. Put a new rectifier and cap on the board because i had one sitting around. DC power is steady on the scope. All good.
Using my scope, i have determined that there is no audio signal leaving the FM front-end section. Input voltages to this little box look correct and match the schematic, but there is not a peep coming out as i slide the tuner around. It is easy for me to compare with a working model that i have sitting right next to it so this suggests a problem in the front-end itself.
Can anyone suggest a likely culprit inside the front-end? It is a bit difficult (meaning impossible) to get probes in here because it is all recessed into this little box
It almost seems like the easiest thing to do is to keep an eye out for a replacement front-end. Were these things interchangeable at all between the 3000, 4000, and 4400?
Thanks,
Jeff
Some versions share frontend modules, - but not all.Does your Beomaster 4000 tune to 104MHz or 108MHz on the dial?Does the tuning voltage vary when you try to tune in stations?
If the frontend box still has a small sticker with its partnumber on the side, please tell me the number and I'll see what I can find in the dungeons.
Martin
Hi Martin-
My 4000 tunes up to 108MHz on the dial. The tuning voltage varies from about 6.2V at 88MHz to 22V at 108MHz.
The sticker is still on the side of the box. It says 8050054.
Thanks much for the advice,
https://beoparts.com//?s=8050054&search=Go
I finally got around to installing the front end you sent me. I have FM again in my 4000. Strong signals, tuning meter and lights work. My only problem is that it looks like the stereo decoder is not working. (no green light, no difference in sound if you press the "mono" or not).
Is there an obvious place to start with a decoder in a 4000?
Thanks
I managed to figure it out by tracing the 19khz stereo signal. I had the rectified 38Khz waveform on the base of TR21, but nothing coming out of TR21. Checked the DC voltages and the base and emitter were equal which meant the transistor never fired. Traced the problem to TR22 which was bad (you can test for this by shorting the two test points in the neighborhood of TR22 which effectively turns it "on"). I replaced the transistor and presto - stereo signal again.
Good job!