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
Hi all,
My beomaster 8000 has developed distortion in the right channel, independent of volume, it is present on all sources.
I suspected the offset so replaced the old original pots with new (precision) trimpots and did adjustments last week. This temporarily solved the problem. The BM was recapped 3 years ago.
Right channel offset drifts to 20-30mV every time after a few days, I have readjusted two times now.
I am thinking one or more bad input transistors (TR201, TR202), or maybe a maybe a bad solder joint on the right amp PCB.
Am I on the right track? Any measurements I can take to confirm suspicions?
Should replacement transistors be a matched pair?
I read this thread, don't think it is the same problem though because I have a drifting offset.
Would love to hear your thoughts on this.
Which Offset? The 0 mV at the output-stage or the idle current (18mV)?
Did you replace C205 and C211? Cold/Heat may infuence the setup.
The DC offset at the output stage, it suddenly drifts away from around 0mV to 20-30mV after a few days when the symptoms appear.
C205 and C211 were replaced 3 years ago so not prime suspects but maybe one has gone bad early.
Distorsion doesn't mean anything unless correlated.
Do you have crackling sounds?
Distorsion could be many things like bad solders or broken tracks after a careless re-cap, or bad power darlingtons.
Please tell us more!
Jacques