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Need advice on fixing a broken knob...

Last response: in Other Consumer Electronics
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March 25, 2011 12:04:55 AM

Well, I'm not sure where to post this question (or whether it should even be on this forum), but I like the Tom's Hardware community, people here seem to know what they're talking about.

The problem is a broken knob on my guitar amp.

Here's a pic:



As you can see, the knob is gone, but the shaft of the pot is broken as well (so I can't just slide a new knob over it). This makes putting a new knob on difficult. Do you have any suggestions? I've already tried to use epoxy (resin), but there isn't enough surface area for a good enough grip. I twisted the epoxy'd knob a couple times, and it snapped right off.

Have any of you ever had a similar problem? Can you help me out?

I appreciate your time and any advice you can offer.
March 25, 2011 8:38:24 PM

two choices..
get yourself a tiny flat head screw driver and get the tip really hot.. then press it into the shaft to melt a line.
this allows you to adjust the dial by inserting a flat head screwdriver into the slot you melted into it.

or

get yourself an accurate multimeter and remove the dial.
connect the multimeter to the dial pins and spin the dial all the way one side.. take the resistance measurement.
then turn the dial all the way to the other side and take another resistance measurement.
go buy a new dial that has the same resistance values.

if you cant rotate the dial as it is.. you need to use the flat head to melt a slit into the shaft.

i had a shaft break on an air conditioner.. and instead of replacing the switch, i used a screw driver to melt a slit into the plastic shaft.
i used the screw driver to adjust the switch from there on out.

my mother had a large air conditioner that had the knob snap off.. and i bought a replacement switch for it.
but when i got home, my mother had already removed the wires from the switch.
i had no idea what wires went where.. and i hooked the switch up anyways to see some sparks.
that house was a lot of bad memories.
March 26, 2011 9:46:34 AM

Hey, I love your flathead screwdriver idea. I'd been thinking of drilling down in ever so slightly so there was an empty space w/more surface area for epoxying, but the flathead screwdriver idea is much more elegant.

I've also considered buying another pot altogether, but the risk value of me screwing up the wiring is too high (there's about 150 watts of power going through two 12 inch speakers). If I screw up, I'm bound to fry my speakers or blow them out... or electrocute myself.

Anyways, I love your suggestions. I bet I'll be able to try something with the flathead idea .

In the mean time, are there any other suggestions? Like maybe something obvious that I'm missing? I appreciate any help.
!