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Seeking advice on the best way to realign C33 tone control knobs

Ricktptman

Ricktptman

High Fidelity Enthusiast
Subscriber
I've done it many times with other (less rare and expensive) knobs on my Pioneer/Marantz restorations, but they're much easier to come by if "the worst thing" happens.

One was loose when I acquired the preamp and I've corrected it so the marker on the aluminum outer part of the knob aligns with the marker on the glass faceplate.

The other FOUR are all pointed at 1-2 O'Clock and taking a slot-tipped screwdriver and gently trying to break them loose isn't working.

If anyone has first-hand advice/experience regarding this, I'd really appreciate some suggestions. These knobs all cleaned up to essentially "mint/near mint" condition and I have no intention of "boogering" them up. I can live with them this way, but this is the last thing on my "restoration" list of things to do. I just finished the LED conversion and it went very well. The 33 is SO much less difficult to work on than my 28 was. The removable modules were a real step forward. TIA for any assistance.
 
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Please explain. Without the knob on the shaft, is the flat spot on the shaft aiming correctly upward? If yes then your problem is with the flat spring steel piece stuck inside the hole on the back of the knob.
 
The switches are installed and oriented correctly as they can't be installed otherwise. The tab on the pot won't let them be installed at any other angle. I believe the flat spots are on the BOTTOM, not the top, but I'll go back and double-check. The spring steel pieces are correctly oriented in the slots. I checked that already. All I need to know is the BEST way to break the outside aluminum part loose from the inside black plastic part. Again, I've tried to gently get the inner part to turn loose using a flat blade screwdriver against the flat spring steel piece, while holding the knob by hand, but I can't get it to break loose. The next thing I've thought about trying is to use a hair dryer or heat gun, but that poses execution challenges as well. I'd have to wear gloves in order to get a purchase on the knob while it's still warm and I obviously don't want to OVERHEAT the interior plastic piece. I appreciate the help though, jlovda. You're always one of the first on the scene to try to help and that's appreciated...
 
I'll post a picture as soon as I get a picture of it compressed. (I wish you could upload larger file size photos.)
It's basically as I described it earlier. They all point to 1 or 2 O'Clock and not "12 noon" as they should. All of the flat spots on the pots are the same. They are all on the bottom side of the shaft and parallel with the rest of the preamp on the horizontal.
 
I have an MA6200 amp with the same five band EQ. You are right, the flat spot is on the bottom. I have never seen a knob as far off as you state since you would probably break the pot if you forced it off that far, especially FOUR of them. Sorry, I cannot help. Good luck.
 
Okay, will do. I'll report back...I did get some inspiration from Jlovda's focus on the steel flat springs. If I pull them out and use a wooden cleaning swab (broken off flush in the surrounding open portions of the plastic) to compress the plastic inner portion onto the shaft, it increases the friction to approximately the same as when the flat spring is installed. I can keep the flat springs if a future option avails itself. I tried it with one, and frankly, it works really well considering...
 
I have had a few knobs where the inner shaft receptacle has broken loose and a little super glue fixed that. But trying to break loose that receptacle intentionally has never been an issue for me. Maybe find an old potentiometer shaft that you can place in a pair of vice grips on and a vice with soft jaws to hold the knob My DAD use to place lead over the jaws of his vices when he didn't want to marr the surface and would allow you to to rotate the receptacle as necessary.
 
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