leosagna
New Member
Hi everyone!
I recently picked up my first Mc, a MA6100 Integrated in great condition!
Everything electrically seems to be working great besides the volume pot. From what I've read, this is not uncommon for this unit, but my problem seems to be slightly different than what I can find on the forums.
Issue: When turned on, the left channel comes on at 9ish o'clock on the volume position and tracks very smoothly up as the volume is increased with no issues. The right channel on the other hand does not. It is very very (very) faint consistently from 9 to almost 1 o'clock. At the 1 o'clock position, the right channel sort of pops/thumps on to match the volume level of the left channel. From 1 o'clock to full CW position both channels increase completely in unison, balanced.
Playing with the balance or loudness controls doesn't have any effect on the right channel until after the 1 o'clock position is reached. Once reached, the right channel is effected normally by these controls (and the left channel is effected normally thru out the whole rotation). I've flushed all of the switches with Deoxit and pots with D5 Fader with no change.
I've ruled out the power amp section using the reverse channel control selector, and by removing the pre-out to power-in jumpers and trying another power amp. Same issue, except when the channels are reversed the left channel acts like the right, and the right is fine.
I soldered the grounding crimps to the cable shields (as some have suggested here) and re-soldered some questionable joints on the PCB.
Does this sound like it is the pot or maybe a transistor acting up on the preamp board?
If it IS the pot, I'm having trouble finding a replacement for schematic pot with the switch at 700k (shocking...).
I can on the other hand find a dual deck pot with switch for 800k with 400k tap for loudness like the ones used in the C28 and MR55. Would this be a compatible or affect the volume/loudness curve much?
I'm going to completely restore soon this amp but would like to get the volume control working in the mean time.
Any help is GREATLY appreciated!
Thanks!
I recently picked up my first Mc, a MA6100 Integrated in great condition!
Everything electrically seems to be working great besides the volume pot. From what I've read, this is not uncommon for this unit, but my problem seems to be slightly different than what I can find on the forums.
Issue: When turned on, the left channel comes on at 9ish o'clock on the volume position and tracks very smoothly up as the volume is increased with no issues. The right channel on the other hand does not. It is very very (very) faint consistently from 9 to almost 1 o'clock. At the 1 o'clock position, the right channel sort of pops/thumps on to match the volume level of the left channel. From 1 o'clock to full CW position both channels increase completely in unison, balanced.
Playing with the balance or loudness controls doesn't have any effect on the right channel until after the 1 o'clock position is reached. Once reached, the right channel is effected normally by these controls (and the left channel is effected normally thru out the whole rotation). I've flushed all of the switches with Deoxit and pots with D5 Fader with no change.
I've ruled out the power amp section using the reverse channel control selector, and by removing the pre-out to power-in jumpers and trying another power amp. Same issue, except when the channels are reversed the left channel acts like the right, and the right is fine.
I soldered the grounding crimps to the cable shields (as some have suggested here) and re-soldered some questionable joints on the PCB.
Does this sound like it is the pot or maybe a transistor acting up on the preamp board?
If it IS the pot, I'm having trouble finding a replacement for schematic pot with the switch at 700k (shocking...).
I can on the other hand find a dual deck pot with switch for 800k with 400k tap for loudness like the ones used in the C28 and MR55. Would this be a compatible or affect the volume/loudness curve much?
I'm going to completely restore soon this amp but would like to get the volume control working in the mean time.
Any help is GREATLY appreciated!
Thanks!
