Hi everyone.
This is my first post. one of both excitement and some challenge.
like many of you, i grew up in wonder of the beomaster 2400 and decided to relive that, by buying a good condition working 2400-2 beomaster with S50 speakers. I love it...
This unit has recently just has a capacitor replacement kit done throughout the main board. But recently the left channel has been inconsistently failing. I have moderate (hobby) level electronics fault/finding knowledge and sufficient tools, so am keen on solving this myself. That's part of the fun isn't it??
fault description:
Upon turning unit on, left speaker will be dramatically lower volume than right. With my ear close, i can hear the speaker working. First check,w as to move the balance slider back/forth, yet it works perfectly when this problem is not happening (no crackle or inconsistency) and makes no difference to the fault when it is. I am ruling the balance out as a problem.
When failing, the left channel will be 95% quieter on both LF and LR. (RF and RR remain perfect). I have swapped speakers back/forth. the problem remains at the left channel/s output, which rules out the speaker, cables, connections etc.
I have then used both Line-In and FM channels to prove that the problem carries across any input source. Interestingly though. I have on a few occasions switched between FM and Line-In source and the channel has recovered at that change. Once recovered it seems to continue just fine until next power up of the unit.
i took the back cover off and while it was cold, went around the PCB's just giving them a nudge/flex with the back of my driver to see if i could get any dry-joint noise in any area. no luck so far. I rechecked all the capacitor re-solders all looks OK. (BTW - i have not replaced the D50 Bridge Rec, but have been thinking to do it anyway)
when it does fail, or about to, i hear the volume in left channel become muddy, a little crackly or gravelly (if that makes sense) and then fades out to 95%+ gone.
my thoughts...
a) if it occasionally fixes itself when i switch between input source and then remains good, i am thinking a transistor or a cap is failing and presenting that line to switch. When moving between input sources it is just getting enough of a kick to fire up.
b) when working its clean and consistent. No noise from moving balance, treble, bass. So i feel not of concern.
c) the fact the main PCB is all re-capped and the output amp seems consistent. I am leaning towards starting to hunt around the pre-amp area
d) maybe a way to prove if pre-amp was a problem would be to hook up something to the phono and not use the line in. If Phono works perfectly, then its really points me to pre-amp / line-in area as a start (assuming that the FM tuner also produces line-level, so what i experience at external line-in could be also expected of its internal FM tuner)
Sorry for the long 1st post. but i thought i may as get down where i am up to... any advice would be greatly appreciated
John
Could be a bad switching diode but most likely to be a bad balance potentiometer.The small bronze contacts under the black sliding bridge breaks off and contact is lost.A very faint sound is quite normal in these cases due to "overhearing".A repair kit is available, containing new plastic bridge parts.
Martin
Thanks Dillen,
your explanation makes sense.
Is the fault something visual I could verify? I have no problems pulling the unit down and am just looking for guidance. Once in the right track, I would happily purchase the kit and replace a bulb on FM3 that is out at the same time.
Luke