Hi:
I had a similar problem crop up with my BeoSound 2300 a while back. My symptoms were very much like yours in that I would hear a "pop" when I changed stations, changed CD tracks, etc. When I finally got down to the troubleshooting process, I noted that the "pop" was only coming from my right speaker (thus, a right channel problem) and I also noticed that the "pop" was not altered by an increase or decrease in volume. It was at the same volume whether I had the unit volume set high or low.
I'm no electronics guru but I decided to give it a go and referenced the service manual for the BeoSound 2300. After some study, I noticed on the preamp board a P-L MUTE circuit that was in some way connected to the HEADPHONE output and interestingly, fed back to the PowerLink socket without having any involvement with the VOLUME control circuit. For good measure, I plugged in my headphones and noted that there was something not right on the right channel... If I remember correctly audio was absent but I could still hear the "pop".
On this particular unit, the P-L MUTE circuitry is made up of two tiny SMD transistors and two 8.2K ohm resistors which are mounted on a very small 4-pin sub-board which stands at a right angle to the main board. After carefully desoldering and removing the small 1" x 1" board, I tested the transistors in circuit with my DVM and, low-and-behold, the Right SMD (surface mounted) transistor had a short between the junctions. Just to be sure, I probed the other (left) transistor and it read - as best I could tell - healthy with no shorts at all. I further measured each of the two resistors - also in circuit - and they read fine.
The SMD transistors for the P-L MUTE circuit are 2SC4213 as TR1 and TR2. I was only able to find them on eBay from a China based seller. I ordered a couple and they arrived about 2 weeks later. I used Chip Quik to remove the right channel 2SC4213 SMD transistor so that I didn't damage the traces. I tested it one more time out of circuit and it was definitely shorted at the junctions. I then mounted my smallest solder tip and proceeded to carefully solder mount a new 2SC4213 checking after wards with a 10X loop to make sure that the joints were good and that no solder shorts were left behind. I then re soldered this P-L MUTE board back onto the Preamp board.
My problem was solved as the repair worked perfectly. No more "pop"!
After reading about your issue, I referenced the BeoSound 9000 Service Manual and, although not identical to the circuit layout of the BS 2300, the BS 9000 does have a P-L MUTE circuit and as part of that circuit has two 2SC4213 SMD Transistors. But, not being an electronics technician, I am unable to problem solve any further.
Hopefully, some of the other more knowledgeable Beoworld contributors can chime in here and help you along.
Good luck!
Michael
Lowell, Massachusetts, USA
