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That was a bit tedious. Eleven pots later and they appear noise free.
The PEC pots are quite robust and seem to have the potential at least to be great. But they're not perfectly assembled.
The crackling noise probably came from the fine carbon dust / particles that most of the pots had to some degree in the area of track and wiper.
I cleaned everything with 98% alcohol and Q-tips. Wiping the track, the dust was enough to blacken the cotton tips and you could see small black particles.
There was very little in the way of grease on the shafts except for one pot which had too much and it had spread around inside.
After reading a lot of info on the net I opted for the nothing-but-alcohol strategy for the wiper and track. The track is very smooth and more plastic than carbon.
The wiper is a little, loose, shaped piece of carbon with three nibs protruding, one which is the electrical contact and two others which ride on a brass ring set into the track piece.
I put a bit of grease on each shaft before reassembling. I just used some bicycle bearing grease I had close by. After reinstallation I added a small drop of fairly thick clear machine oil to the retaining clip and brass washer where the shaft enters the pot and wiped the area immediately after turning the shaft back and forth a bit.
Looking at the output of a sine wave on my scope, the controls vary the trace very smoothly with none of the horrible static/noise that appeared before.
The PEC pots are quite robust and seem to have the potential at least to be great. But they're not perfectly assembled.
The crackling noise probably came from the fine carbon dust / particles that most of the pots had to some degree in the area of track and wiper.
I cleaned everything with 98% alcohol and Q-tips. Wiping the track, the dust was enough to blacken the cotton tips and you could see small black particles.
There was very little in the way of grease on the shafts except for one pot which had too much and it had spread around inside.
After reading a lot of info on the net I opted for the nothing-but-alcohol strategy for the wiper and track. The track is very smooth and more plastic than carbon.
The wiper is a little, loose, shaped piece of carbon with three nibs protruding, one which is the electrical contact and two others which ride on a brass ring set into the track piece.
I put a bit of grease on each shaft before reassembling. I just used some bicycle bearing grease I had close by. After reinstallation I added a small drop of fairly thick clear machine oil to the retaining clip and brass washer where the shaft enters the pot and wiped the area immediately after turning the shaft back and forth a bit.
Looking at the output of a sine wave on my scope, the controls vary the trace very smoothly with none of the horrible static/noise that appeared before.
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