I don't know how you guys do it!

[Chuck H]

Fixing a Crate V32 right now. Really bad pots seems to be the problem. One pot has a failing wiper. Two others might just be dirty, but may also be bad. Searching on line I see that this is a really common problem for these amps, sooooo... Not being a repair guy I made a silly, rash decision to just replace all the pots and eliminate a weak link from the design. So I just pulled all the pots. Now I can't find suitable replacements @#%&! I thought they'd be something common in a 16mm size. Nope. They have a rather long bushing that serves to space them from the front of the chassis to the board. I wasn't even able to find a line of pots that could be reasonably made to work (like a long barrel and a back nut or something). In the end I conceded to use plain ol 16mm solder lug pots flipped over with leads off the board. Having done this before. So I've worked out my solution. No problems. My point is...

Taking the amp apart, removing the board, removing the pots AND the ridiculous time I spent trying to find drop in replacement parts make any reasonable cost of repair for an amp like this impossible! And I seem to run into this sort of thing often when I do repairs. I don't envy my comrades here that have to make a living at this work. I understand that a familiarity with the process must help, but it still can't be easy having to source hard to find parts or retrofitting something different on a regular basis. Hat's off to you all.

[Enzo]

Chuck. What are the numbers on the backs of the pots? ANy numbers like 70-103-22?

I have listed a number of Crate pots in the flea market section. Are any of those parts you need?

Don't make me go look up the V32 file myself.

[The Dude]

......Taking the amp apart, removing the board, removing the pots AND the ridiculous time I spent trying to find drop in replacement parts make any reasonable cost of repair for an amp like this impossible! And I seem to run into this sort of thing often when I do repairs. I don't envy my comrades here that have to make a living at this work. I understand that a familiarity with the process must help, but it still can't be easy having to source hard to find parts or retrofitting something different on a regular basis. Hat's off to you all.

Believe it or not, what's often worse (at least for me) is when the customer doesn't want to fix it. I'll explain. I don't like to send anything out of my shop "halfway done". That's just a personal anal retentive thing for me. I also don't do things the customer didn't ask for without talking to them first to avoid "surprises" at pick up time. So, here's a scenario I see on occasion.

Customer brings in a dead amp. The main PCB has to be removed to fix the amp to replace maybe a bridge rectifier or something of the sort. I notice while the board is out that several pots are broken or non-functional. I call the customer and tell him he should replace them now while the amp is broken down- saving labor in the long run and the only additional cost will be a few bucks worth of pots. He declines because he doesn't want to pay the few extra bucks.

It's the customer's amp, so he gets what he wants, but it drives me crazy to not fix something that needs attention.

[Chuck H]

Oh, I checked there! I saw the post today when was searching the forum for possible solutions to my lack of experience Another day in the life, really.

[DRH1958]

This won't help to fix the problem but interesting.... http://music-electronics-forum.com/t11813/

[TomCarlos]

Chuck.... I echo your pain. I too am always concerned that I am chasing the wrong tail. One thing this forum and others have taught me is to take some time to fully understand "what is the problem and where does it originate?" From there, you begin to work forward.

About those pots in the Crate... I recently experienced something similar with a Peavey amp. Finding the older Dual Concentric pots is getting VERY HARD. I was able to find one from eBay. But I then lucked out... I was able to find a "donor" amp - one that had a very bad cabinet but the electronics were still in good condition (at a very cheap price). I ran a "Wanted Ad" on Craiglist. Took a couple weeks but I got a reply. So "picked" that amp for parts. After using the entire Preamp board, I ended up with a main power board that is still working, a nice Black Widow speaker, and the dual Piezo horn.

Since I do this as a hobby and volunteer my services to a local high school music program, they are ok with "used parts" approach. If you get stuck, maybe that too can be your "Plan B."

Oh, one other thing... the link DRH provided for the Palomino, I used that trick to fix a Crate. So before starting on any repair, I try to do a thorough search for repair threads and see if I have similar problems to something that has been discussed and resolved on MEF and other boards. This approach has been a life saver. I owe lots of beers and thanks at a future MEF convention.

[Chuck H]

Oh, one other thing... the link DRH provided for the Palomino, I used that trick to fix a Crate. So before starting on any repair, I try to do a thorough search for repair threads and see if I have similar problems to something that has been discussed and resolved on MEF and other boards. This approach has been a life saver. I owe lots of beers and thanks at a future MEF convention.

I ordered the appropriate chassis mount resistor with the pots today I'm going to mount it on the OUTSIDE of the chassis on the underside of a thick aluminum plate that I'll then mount to the chassis on standoffs.

[Enzo]

So what was your solution? My first thought was to call Loud and see if they have them.

Of all the parts in an amp, pots are almost always custom for the OEM.

[Chuck H]

So what was your solution? My first thought was to call Loud and see if they have them.

Of all the parts in an amp, pots are almost always custom for the OEM.

Right. And this is a long discontinued amp. It looks like the parts I need may have been used on a Mackie or Ampeg product too. I found a parts catalog for these brands that included them. So far, no answer from that vendor. Just as well. The parts were a little over priced in Euro and frankly, I'd rather not.

My solution is to use regular 16mm pots and mount them upside down. I'll run short leads off the board before installing the pots and then solder them to the pots. I've done this before to effect repairs with parts on hand. This amp has a gain channel and I suppose I have a small concern about adding a tad of lead or confounding proximity. There's enough stabilizing circuitry included that it should be fine. It's really not hard to do it this way. I'm sure I'm not the first. Not even on this model. I'll be changing knobs too. I have a set on hand. even getting all split/knurled shafts in one brand for all values was proving problematic and I've read that the geometry is a hair off from standard. This amp was going to the trash if I didn't fix it. I'm not worried about a little wiring cheese and non stock knobs devaluing it

[drewl]

Usually after a while you build up an inventory of replacement parts where you may have to spend some money to fix the amp at hand, but next time a similar unit comes in you already have the parts needed.

[nevetslab]

Cleaning pots instead of replacing them....

I run into the pot issue all the time. With older discontinued products, you rarely find a form-fit-function replacement, as Enzo indicated....pots are generally custom fit for OEM products. Most single gang pots can be taken apart for thorough cleaning, and re-assembled with freshly lubed resistive track & wiper, assuming there isn't breakage of the resistive wafer or damage to the wiper. A typical procedure shown below:



Having a nice assortment of less-common electronics tools, my Erem 71AE Flush Cutting 45 deg diagonal cutters make a great tool to open up the metal flaps holding the stamped metal cover on, which then get straightened a bit with needle nose pliers, removing the cover to expose the inner pot workings. In the style where the wiper mechanism is staked into place, I just brush in Caig DeOxit, coating the resistive track and work it onto the wiper track further within, and rack the shaft back and forth to clean the wiper contacts. Closing up the control is easy enough. I've found one of my Optima IC removal/insertion pliers (505J-US, cut down to 8-pin DIP size) makes a perfect tool for the task, though larger needle nose pliers work quite well to fold the tabs back over.

Multi-gang pots rarely allow opening up as single gang pots do. Best I can do on those, is applying the lubrication with the small brush thru the opening above the metal tabs, and rack the pot shaft back and forth to spread the contact cleaner. I'll also apply some clamping force to the rivets that hold the metal solder tabs in contact with the wafer's resistance ends.....tiny machinist vise....delicate touch, as this could break the wafer (never broken one yet)....have saved pots with loose mating tabs though.

Saves having to search in vain for a direct replacement, or something that will suffice, but then leaves you with the wrong shaft type for the knobs. It's a bit more work than just spraying cleaner in thru whatever opening you can get at (without taking the pot off the board or unsoldering the wires).

[Enzo]

Yep, flush cutters are real god for getting under the tabs that hold these together.

I will usually dismantle a pot before I go to cobble something else into the hole. What is there to lose at that point? Crap can build up on resistive stripes that don't spray away easily, but a wipe with a Deoxit soaked Qtip often works wonders. The pots also have the springy wiper. Some are plain, and are easy to clean, remove any build up. But some are bifurcated, meaning the tip is split into fingers, like a fork. Little bits of fibrous debris can get stuck in between those fingers. It won't spray away, but is easily cleaned when the pot is apart. The tip of my Xacto knife pushes it out conveniently.

A very common problem is a snapped off shaft. Sometimes I don't have the right pot, but I have others of a different value but the same mechanical type. So I take a new pot apart, steal the shaft assembly, and put it in the old pot. That trick works for sliders real well.

[drewl]

Oh yeah, I've taken apart and rebuilt many pots.
Common problem on the plastic pots on solid state Marshalls is those tabs that hold it together start spreading apart.
Push them back down with needlenose pliars after cleaning usually does the trick.

All this stuff becomes second nature after doing it for a while.

[Chuck H]

Cleaning may have worked. Maybe not. It turned out there were other issues that deserved attention anyhow. I added a post to a long running thread about these amps because I thought it might help someone. Rather than cover it redundantly in this thread I'll just link the other. Post #141

http://music-electronics-forum.com/t11813-4/