Sam08861
Super Member
OK, so I've installed the Jim Mcshane kit, Jim Mcshane matched tubes, new lights, mpx capacitors, and the IBBA on my fisher 500b.
The unit seems to be fully functional with the exception of one thing.
The left channel is almost silent and can only be heard very faintly when the volume is turned up pretty high.
However, when the loudness contour switch is turned to 'on' then there is sound from the left but it is tinny and scratchy and not full sounding while the right channel is very full and natural. Also, it maxes out in volume approximately 1/3rd of the way while the right channel has full range and gets louder.
Things I've done to troubleshoot:
1. Tried multiple inputs/sources, including FM, Phono, Aux, etc. All work the same.
2. Tried switching 12ax7 tube for the following to see if it switched sides. (it didn't) -- (phase inverter, tone control amp, phono pre-amp)
3. Cleaned, cycled, lubed and recycled all of the switches and knobs many many times.
4. Cleaned and tightened all tube pin connections.
5. Cleaned and tightened all remote plug pins.
6. Double checked the test points on the IBBA, all are very close as they have been balanced and biased.
7. Double checked the connections that dyche01 pointed out in his thread for the same problem.
8. Double checked the phase inverter settings and these have been dialed in to be within .01 ohms of each other.
9, Double checked that the chan a and chan b phono level pots are both turned all the way up.
10. Tried switching the phase reverse, no change.
11. Cleaned and reseated jumpers in the reverb section.
Any suggestions on how to trace this out or any other suspects given the odd behavior with the loudness switch? Seems only the highs are getting to this channel and not the mids/lows, and only with the loudness switch on.
Be glad to take any readings or pictures that you think might help troubleshoot!
Thanks!
The unit seems to be fully functional with the exception of one thing.
The left channel is almost silent and can only be heard very faintly when the volume is turned up pretty high.
However, when the loudness contour switch is turned to 'on' then there is sound from the left but it is tinny and scratchy and not full sounding while the right channel is very full and natural. Also, it maxes out in volume approximately 1/3rd of the way while the right channel has full range and gets louder.
Things I've done to troubleshoot:
1. Tried multiple inputs/sources, including FM, Phono, Aux, etc. All work the same.
2. Tried switching 12ax7 tube for the following to see if it switched sides. (it didn't) -- (phase inverter, tone control amp, phono pre-amp)
3. Cleaned, cycled, lubed and recycled all of the switches and knobs many many times.
4. Cleaned and tightened all tube pin connections.
5. Cleaned and tightened all remote plug pins.
6. Double checked the test points on the IBBA, all are very close as they have been balanced and biased.
7. Double checked the connections that dyche01 pointed out in his thread for the same problem.
8. Double checked the phase inverter settings and these have been dialed in to be within .01 ohms of each other.
9, Double checked that the chan a and chan b phono level pots are both turned all the way up.
10. Tried switching the phase reverse, no change.
11. Cleaned and reseated jumpers in the reverb section.
Any suggestions on how to trace this out or any other suspects given the odd behavior with the loudness switch? Seems only the highs are getting to this channel and not the mids/lows, and only with the loudness switch on.
Be glad to take any readings or pictures that you think might help troubleshoot!
Thanks!
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