Home » VintageKustom.com » Repairing Kustom Amps » K250-1 Knob Removal (can't get the knobs off)
K250-1 Knob Removal [message #20340] Mon, 17 March 2014 22:37 Go to next message
retroamped is currently offline  retroamped
Messages: 4
Registered: March 2014
Location: Fort Payne, Alabama
Junior Member
I'm going to be mixing-and-matching two K250s with issues to get one really good one. I'm embarrassed to admit I can't get the knobs off. I assumed they are push-on on a d-shaft. I don't see any set screws. I tugged pretty hard and can't get any to budge. I'm afraid to pry 'em for fear of breaking something original. Can I get some advice?
Re: K250-1 Knob Removal [message #20341 is a reply to message #20340] Tue, 18 March 2014 00:49 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
Yes, they should be D shaft push on with no set screws. I've seen them get stuck on so hard that if you try and pry them up, you will crack the knob or pull the shaft out of the pot.

I think that the problem is the spring metal insert that is inside the knob rusts or corrodes itself to the pot shaft.

Set the amp face down and then spray a little WD-40 under the knob so that it can seep down into the knob/shaft area. Let it sit for a little while and then try to pull the knob off.

If you do break one, you can replace them with the set screw type that is carried at Small Bear Electronics. They are an exact match to the originals, with the exception of the set screws.
Re: K250-1 Knob Removal [message #20342 is a reply to message #20340] Tue, 18 March 2014 06:58 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
I have had the same issue.At times I have had to pry the center round aluminum trim off of the knob and drill a hole in the center( yes this wastes the knob(s) and then spray PB blaster down the shaft.
PB blaster is the untimate rust breaker on the planet and most auto parts stores stock it, if you work on your car or lawn stuff you need to have it on hand anyway!
NOTE, that if the knob is that badly rusted or stuck on the pot shaft that if you are removing the knobs to get that circuit board off the front of the amp than the pots retension nut may be even more of a pain to get off!
Many times I have had to cut across the nut with a small cut off disc in a Dreamel tool.
Take your time and if you get frustrated, take a break and come back latter!
What is the issue with the donor K250?

[Updated on: Tue, 18 March 2014 07:04]

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Re: K250-1 Knob Removal [message #20343 is a reply to message #20342] Tue, 18 March 2014 10:57 Go to previous messageGo to next message
zedsalt is currently offline  zedsalt
Messages: 62
Registered: March 2008
Member
Yeah, I have yet to find anything that works better than DeoxIT for cleaning/protecting scratchy pots, but for sheer rust-busting power, PB Blaster is the bomb. If you've ever heard your mechanic extolling the virtues of something he/she referred to as "Panther Piss", and you want to get some for yourself, it's the PB Blaster label you're looking for.
Re: K250-1 Knob Removal [message #20344 is a reply to message #20340] Tue, 18 March 2014 12:19 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
DeoxIT and PB Blaster, two of my favorites.

PB also makes a lot of other spray lubricants as well, that do a great job.
Re: K250-1 Knob Removal [message #20345 is a reply to message #20344] Wed, 19 March 2014 01:57 Go to previous messageGo to next message
Kustom_Bart is currently offline  Kustom_Bart
Messages: 599
Registered: October 2010
Location: Greenville, MichiGUN
Senior Member
I like those two as well ChicagoBill, I also like some stuff called Kroil and I make my own penetrating oil that is the best thing I have ever used, mix equal parts of Marvel Mystery Oil and Acetone and this thins you oil very thin and allows it to run done into very tight places and the acetone evaporates very quickly leaving only the oil behind. Try it out sometime it works great! Smile
Re: K250-1 Knob Removal [message #20349 is a reply to message #20342] Wed, 19 March 2014 10:52 Go to previous messageGo to next message
retroamped is currently offline  retroamped
Messages: 4
Registered: March 2014
Location: Fort Payne, Alabama
Junior Member
One K250 has the exterior (tuck-n-roll, faceplate, knobs) in super good condition but one channel is blown, the polarity licon switch is bad, and there is a devastating loud pop and crackle on power-up (not the normal pop/thud). I got the new donor from ebay - it is on it's way from CA. It is promised to be in excellent working condition but the cab, faceplate, knobs are super bad. When it arrives I plan to swap the internals into the good cabinet. The old one may have some salvageable components to serve as a donor for the new.
Re: K250-1 Knob Removal [message #20350 is a reply to message #20341] Wed, 19 March 2014 20:08 Go to previous messageGo to next message
retroamped is currently offline  retroamped
Messages: 4
Registered: March 2014
Location: Fort Payne, Alabama
Junior Member
Halleleujah! I went with the consensus and got some PB Blaster. I used it just as you described and, after several minutes of soaking, all of the knobs came right off with no damage. Problem solved. Thank y'all for the expert advice.
Re: K250-1 Knob Removal [message #20351 is a reply to message #20350] Wed, 19 March 2014 21:38 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1408
Registered: June 2004
Location: Belding, Mi
Senior Member
Great that you got the knobs removed. One thing on the slant face amps are the molex connectors that connect the boards together have issues with age. Your amp with the blown pre amp, might just be a bad connection at the molex plug. I had a guy give me a Kustom X BiAmp power amp that he said was DOA. Got it home, cleaned all the molex connectors and it came back to life.

Just a thought, unless you can see burned parts on the board, then it's time for a donor.

pleat
Re: K250-1 Knob Removal [message #20358 is a reply to message #20342] Sun, 23 March 2014 01:32 Go to previous messageGo to next message
retroamped is currently offline  retroamped
Messages: 4
Registered: March 2014
Location: Fort Payne, Alabama
Junior Member
Stevem, Thanks for the tip about the pots. On the original amp the pots came off easy, but on the donor machine from Ebay I broke 2 pots trying to take the nut off. I was surprised how little pressure on the frozen nut it took to break the pot (surprised enough to make the same dumb mistake twice) The Dremel did great at cutting the nuts off the rest. I used a high speed cutter bit to cut a slot in the nut almost all the way through and a screwdriver in the slot to twist and break the nut without damaging the threads. The original amp donated 2 pots to the Ebay donor preamp.

Re: K250-1 Knob Removal [message #20361 is a reply to message #20340] Sun, 23 March 2014 07:25 Go to previous message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
Cool deal!
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