Well, as our shared hobby goes, there's nothing much worse than the day your good old workhorse AU-717 (or fill in the blank) develops a case of Acute Volume Pot Seizure. There have been a couple of threads written on this subject, but the results seem inconclusive in some cases, or meandering. (threads naturally wander into cleaning the internals of the sealed Alps pot, etc. This is different)
So this thread is only for the owner's of amps with sealed Alps pots that are starting to resist turning. Now that I have discovered how easy this fix is, I'd recommend it as soon as the knob feels even a little too resistant. My own 717 had reached the point where knob was slipping on the shaft rather than turning (yep, I checked the set screw), and I started to worry that "forcing" it might cause internal damage.
There is a good thread in which Echowars and others recommend getting lubricant into the shaft, and it worked perfectly for me, but there are a few details to share. You will, of course need to remove the volume knob (1.5mm allen) but the good news is that no other disassembly is required. The gap where the shaft enters the pot is very tight, and you are going to need a way to flow a lubricant that won't react badly with the old hardened grease from 1977 (or whenever): a very "thin" lube that flows well. That can always be helped by gravity,
so:
1) A thin lube that plays well with others
2) the amp will have to stand up on its rear so that the volume pot shaft is vertical for gravity and capillary action to distribute the lubricant.
3) Applying a little heat (as suggested in another thread) definitely helps move the lube along the shaft.
I recently purchased some Hetman Synthetic "Light Bearing and Linkage Lubricant 13" for use on tuner capacitor bearings (but never, ever on the fins). Whatever you use, make sure it says "compatible with petroleum-based oils". Synthetics are generally thin, easy to flow, and won't break down in this century. This particular product was really designed for use on musical instruments, especially horn keys, where it is hard to remove 100% of the old lubes. It also has a long, very thin, metal pipette to deliver the oil (just about perfect for this task).
My 717 has two rear plastic bumpers that make it easy to stand on its back. I think the bumpers were supplied with rack ear kits? Convenient, but if you don't have these, I guess a couple of wood blocks should work: just be careful of the delicate parts that could get crunched back there. You could even screw the wood blocks into the rear panel using the pre-drilled "bumper holes". (screws are same as side outer case)
Of course, if your amp is torn down for a rebuild, just arrange it so that the vol pot shaft is pointing toward the ceiling.
Use a hair dryer to warm it up. I borrowed a very wimpy travel dryer from my wife, and it took forever. I didn't heat it up enough to start melting plastic, just to the point where the volume shaft was a bit hot.
Then apply the lube around the seam, just a couple of drops. Clean up any that gets on the Alps plastic case with a paper towel. I let it soak in for about 2 hours (a basketball game that, unfortunately, my Tarheels lost. Sigh).
Next, check for any broken down black, goopy old grease that has seeped out, and clean this off. I then added another drop or two of lubricant, and waited another hour or two. Leaving it overnight might be better, but I didn't.
Next, flip the amp back to "normal position", and clean the shaft (alcohol on paper towel) to make sure none of the lube is on there: the set screw has to clamp, and you don't want it slipping. Once the pot is in place, work it very slowly around. You should already feel a big difference. Areas that were especially tight before might need some extra turns, and if it still feels stuck you probably will need another pot from a donor unit.
This worked so well on my AU-717 that I am amazed to think that this is the way it "turned" when new. The click stops feel much more precise. I hope this works for you, as well.
So this thread is only for the owner's of amps with sealed Alps pots that are starting to resist turning. Now that I have discovered how easy this fix is, I'd recommend it as soon as the knob feels even a little too resistant. My own 717 had reached the point where knob was slipping on the shaft rather than turning (yep, I checked the set screw), and I started to worry that "forcing" it might cause internal damage.
There is a good thread in which Echowars and others recommend getting lubricant into the shaft, and it worked perfectly for me, but there are a few details to share. You will, of course need to remove the volume knob (1.5mm allen) but the good news is that no other disassembly is required. The gap where the shaft enters the pot is very tight, and you are going to need a way to flow a lubricant that won't react badly with the old hardened grease from 1977 (or whenever): a very "thin" lube that flows well. That can always be helped by gravity,
so:
1) A thin lube that plays well with others
2) the amp will have to stand up on its rear so that the volume pot shaft is vertical for gravity and capillary action to distribute the lubricant.
3) Applying a little heat (as suggested in another thread) definitely helps move the lube along the shaft.
I recently purchased some Hetman Synthetic "Light Bearing and Linkage Lubricant 13" for use on tuner capacitor bearings (but never, ever on the fins). Whatever you use, make sure it says "compatible with petroleum-based oils". Synthetics are generally thin, easy to flow, and won't break down in this century. This particular product was really designed for use on musical instruments, especially horn keys, where it is hard to remove 100% of the old lubes. It also has a long, very thin, metal pipette to deliver the oil (just about perfect for this task).
My 717 has two rear plastic bumpers that make it easy to stand on its back. I think the bumpers were supplied with rack ear kits? Convenient, but if you don't have these, I guess a couple of wood blocks should work: just be careful of the delicate parts that could get crunched back there. You could even screw the wood blocks into the rear panel using the pre-drilled "bumper holes". (screws are same as side outer case)
Of course, if your amp is torn down for a rebuild, just arrange it so that the vol pot shaft is pointing toward the ceiling.
Use a hair dryer to warm it up. I borrowed a very wimpy travel dryer from my wife, and it took forever. I didn't heat it up enough to start melting plastic, just to the point where the volume shaft was a bit hot.
Then apply the lube around the seam, just a couple of drops. Clean up any that gets on the Alps plastic case with a paper towel. I let it soak in for about 2 hours (a basketball game that, unfortunately, my Tarheels lost. Sigh).
Next, check for any broken down black, goopy old grease that has seeped out, and clean this off. I then added another drop or two of lubricant, and waited another hour or two. Leaving it overnight might be better, but I didn't.
Next, flip the amp back to "normal position", and clean the shaft (alcohol on paper towel) to make sure none of the lube is on there: the set screw has to clamp, and you don't want it slipping. Once the pot is in place, work it very slowly around. You should already feel a big difference. Areas that were especially tight before might need some extra turns, and if it still feels stuck you probably will need another pot from a donor unit.
This worked so well on my AU-717 that I am amazed to think that this is the way it "turned" when new. The click stops feel much more precise. I hope this works for you, as well.
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