The volume control on my Hafler DH-110 is encased in plastic. The control uses an logaritchmic taper. The control is "scratchy" sounding in one particular spot. It doesn't look like there is a way to spray tuner cleaner inside the control?

Disregard the melted power switch. That was taken care of last year.

Sometimes I've had to drill a small hole in sealed pots, but its risky. You could easily hit something vital, or worse, whatever you spray in there may not be able to find a way out. You could also try to disassemble it, even if it requires drilling out rivets. The real trick is knowing where to drill, since what's inside is totally hidden.

To drill the small hole, I use a hand held pin vise with a wire drill bit, something smaller than 1/32. Drilling it by hand rotation gives you enough control to not destroy the inside of the pot when you drill through the shell.

Before doing all this, try just exercising the control about 14 million times, full range back and forth till your arm goes numb. But it sounds like it's going to need some chemical intervention.

That control is made by ALPS. They can be dis-assembled; remove the screws.

I had one of those, the only preamp I ever saw with a volume control knob on the husky remote instead of crummy buttons. Yea you will probably end up removing the dual control from the unit if you have the time and enthusiasm to do so. I cannot say if disassembly is easy or not. As it may be riveted together. But I have done so before and just used other methods like epoxy or something to reconnect the shell parts together, with a vise or clamp to hold it till it dries. Or have even replaced small rivets with #2 screws and nuts if they fit. Have you checked the part number of the pot and done a search for new or NOS replacements? If it is an ALPS there may be some floating around somewhere as compared to an unknown brand.

I have heard of people turning the control end to end a couple dozen times to see if they can redistribute any residual lube. Sometimes they puddle fader lube on the top seams and enough seeps in to do the job. You could easily damage that pot if you try to disassemble it. As long as it's not noisy in the section you normally use, leave it.

The picture is self explanatory, the sleeving will not allow the drill bit to penetrate the pot’s body more than a couple mm. Just don’t push hard the drill. Drill bit size no more that 2-2.5mm.
I have done it several times with no problem...and I always hope I won’t have a problem ))

……. Which is why I use a pin vise, not a drill. Way more control. Available everything…..hobby shops for one

I've seen some where there was a hole melted thru presumably by a soldering iron.. safer then drilling and having debris fall inside?

Those pots come apart. Remove it from the PCB and you can disassemble and clean it properly without spraying a bunch of gunk inside.