Looking for trick to keep knobs tight

[dude]

Hi all,

I have a nineties Champ SE amp with D-shaft pots, the knobs are fitting very loose. I've tried paper on the posts but can't seem to get the correct tightness. I got them too tight with paper that taking them off to do repairs pulled some shafts out and ruin the pot.

I've replace the broken pots but still the new shafts are too loose fitting. I don't want to get new knobs, rather expensive for this amp.

Any suggestions?

Thanks in advance,
al 

[Steve_P]

a little nail polish on the tip of the shaft, maybe?

[sluckey]

Do they have a setscrew? Or do they slip on and have a spring steel insert that maintains tension? Or something totally different. Post a pic of the knob.

[dude]

No set screw, no spring, just push on.

Nail polish...?

[kagliostro]

I don't know if you can have good result with this method

I solved the problem cutting a thin piece of aluminium sheet

and pasting it on the plane part of the D shaft

K

[stratele52]

Few turn or just one ( ? ) of plumber Teflon tape may do the job with no damage;


http://www.plumbingsupply.com/tapes.html

[dude]

Yeah, the knobs are just worn, the little indents that make it for a D-shaft are the problem, they are bent over and worn.

They fit so loose that they fall off just tilting the amp forward. The paper I used was printer paper, I had it doubled over and that was too tight, trying single the paper ripped pushing the knob on. I think nail polish may work but a very thin coat, or possibly super glue on the D shaft part, let dry of course.

The aluminium sheet would have to be super thin, I have nothing like that.

I'll try the teflon tape once around, if that doesn't work, I'll try the nail polish. The polish would scrape off easier than the super glue if too thick.

I guess the answer is trying different things till I get it not too tight.

Problem is I've had this PCB bd out so many times modding the OD circuit that the knobs are worn. Last time I use painters tape and after a few years I tried to open the amp and the knobs were so tight the the pots separated inside when taking them off. Just don't want that to happen again.


BTW, what is a C and J tapered pot...? Luckily these unavailable pots for this amp didn't break. I'm only familiar with audio and linear.   

Thanks for the suggestion,
al   

[sluckey]

The aluminium sheet would have to be super thin, I have nothing like that.

Most people have a roll of Aluminum foil in the kitchen.

If you can find some thin spring steel (like that in a steel tape measure) you can make some square inserts like used on old D-shaft push on knobs.

Or put a dab of silicone (bathtub) caulk in the knob just before you push it on. Let cure. Still easy to remove if needed.

[TubeGeek]

A little dab of hot glue may work too.

[stratele52]

A little dab of hot glue may work too.

Sure this will work !  Forget to remove the knob after , but who need to remove a knob ?

[jjasilli]

Maybe it's possible to drill & tap the knobs for a set screw.

[dude]

Maybe it's possible to drill & tap the knobs for a set screw.

Now that's a good thought, I had a bathroom shower knob with a striped huge set screw, I drilled a small 1/16" hole on the opposite side and used a small guitar action setting screw. Work like a charm. I have several cheap (set screws pointer knobs) that I paid a dollar for 10, there too big to fit this amp but the set screws are useable and I have a small tap (might not even need the tap as the Knobs are a rubbery plastic.  Good thought.

I already tried the nail polish and it worked so I'll see.

I gave up on modding the SS preamp OD channel, once I fix the OV "bee sound" something else was created. Luckily the clean channel on these 90's Champ SE's is pretty nice, especially after I took a little treble and bass out.  The SS preamp goes into a tube power section, with bias pot installed I can run 6V6's. I hijacked my own thread, 

Any answer on what's a C-taper and J-taper pot....? My thread, I can hijack it, 

Thanks everyone, you guys are like a walking encyclopedia....

Regards,
Al   

[sluckey]

C - Reverse Log taper

J taper is a softer audio taper where you have around 30% resistance at noon, as opposed to the 10 to 15% found in more conventional audio taper pots.