Replacing Allen Bradley pots

[Wavelength]

PEC makes great pots I had them build me 4 values 100 pieces each and they turned out great. Last a long time and are built like tanks.

 

[soapfoot]

I recall speaking with some support engineers from Alps decades ago and they were adamant about not juicing potentiometers.

I have never seen worn pot wipers effectively rehabilitated by anything other than cleaning. If the pot element is severely worn, give it a decent burial in the bin.

JR

I realize some will think this irrational, but that doesn’t make it less true

Binning an original pot on an otherwise-untouched 1950s Stratocaster or Telecaster (as opposed to restoring it) could be tantamount to binning thousands of US dollars

There are some situations that warrant making every effort to save the original part

 

[rh001]

There is hope for like-new pot restoration and it's this: https://www.worldproaudio.com/Pro-Audio-Extras/WPA-Brown-Stuff-01

Poor brush contact may be due to rough surface due to usage and oxidation.

Neither isopropyl nor F100L will remove oxidation nor polish the surface...WPA Brown stuff does just that. WPA Clear Stuff lubes and protects.

here is entertaining metaphor for feeling after use of Brown Stuff and Clear Stuff:

 

[charlesaudio]

I installed a 600ohm input attenuator made with PEC pots (was expensive) into a 1176 and it last less than 18 months before becoming scratchy.

 

[Wavelength]

I realize some will think this irrational, but that doesn’t make it less true

Binning an original pot on an otherwise-untouched 1950s Stratocaster or Telecaster (as opposed to restoring it) could be tantamount to binning thousands of US dollars

There are some situations that warrant making every effort to save the original part

I was on a plane headed to CES one year and a CTS engineer sat next to me. First question I asked was what do you think of guitar companies soldering to the back of your pots? He said what??? Do they know it's soft carbon. I don't do that at all anymore, I use solder washers and copper foil tape. Second question cleaning pots? No that is really stupid it removes the protective coating we put between the wiper and the carbon. Just replace it... who cares if it has a 1957 date code. Throw those in the case for someone else to noodle over.

 

[sodderboy]

With all due respect to manufacturing engineers, they are never around 20-60 years later after their great design has been living the studio, bedroom, or road life. WWED? What would Engineer do when faced with a Moog with drilled pots and no service history? Replace them with the currently bestest engineered pots of course. That is one option.
I question the can soldering comment, as pot design has not had the element mounted to the metal can in decades, at least those that I have opened. The wiper/element/shaft/body are all assembled together in the can type. Heating the can during a properly designed/trained production operation is not destructive. I cannot speak for someone in their basement with a 25W amazon iron.
Sometimes you can only spray stuff in there and try to blow it out with air, then condition. Yes, that dissolves the element grease, shaft grease, and dirt. Removing the flush is just as important. I do a drill/flush only as a last resort, knowing I can get a replacement. On a SSL 9K, you have no choice with those centralabs switches on some of the pots. Those are unobtanium on a console scale.
Love F100l, but the RGF grease is better for pots if they are opened, and treat it the same as salting in cooking, a little goes a long way. The grease, if you can apply, has better staying power, and is what the manufacturer put on the element at birth.
Brown Stuff? Clear Stuff? I want softtoys raining on me, but I will try that on my personal pots first before using on customer gear. I am timid regarding new "stuff" since a Stabilant 22 incident in the 90's. . .
Scratchy pot after 18 mo? My tele-tech opinion on the 1176 is that DC in the circuit dried the surface element lubricant prematurely. On a Moog, almost all pots are passing DC, so the drill service must have worked for a while then went bad again. There may be hope with opening (if possible), cleaning, and greasing with RGF, a higher quality product than the manufacturer used.
Mike

 

[salomonander]

Maybe someone is smart enough to help me out with another question regarding the minimoog. Do the marked capacitors have any effect on the sound? They are some wet molded tantalums.

 

[Evertide]

C11 + C12 are on the power-rail , so not direct , C13 is...

 

[Brian Roth]

Anyone know the ones by honeywell? They still produce them as well for a decent price.

Honeywell bought Clarostat approx. 20 years ago. According to Honeywell they ceased all Crostat production in 2019. But there is probably some NOS series 53 pots in various warehouses.

https://sps-support.honeywell.com/s/article/AST-Clarostat-potentiometer-replacements

Bri

 

[rh001]

it's not about soft toys, it's about doing everything right and thereby winning more than anybody.



but of course one should try before using on customer's gear. I've been using it on customer's gear for over 15 years. For instance because Brown Stuff and Clear Stuff work so well cleaning every pot and switch on this console was practical. (pots were not sealed so needle tips and spray wand could get inside)

 

[Brian Roth]

As a followup....if replacing a pot on a vintage guitar destroys the value, does that also apply to vintage Minimoogs?

Bri

 

[Evertide]

Is this about repairing and using or selling ?

 

[salomonander]

This is a repair and general service. The customer wants to use not sell it. Regarding collector value and pots i did some digging tonight and i can get the correct AB pots NOS for way less than the PECs…

 

[Brian Roth]

Cool....once you order the replacements that you need, let us know what sources you found. (Don't want to cause a stampede!)

Pots are often tricky to source these days.

Bri

 

[salomonander]

Will do! And thanks again

 

[CalavoBob]

I've had pretty good luck carefully opening the tabs on noisy J type Allen Bradley pots and carefully cleaning the elements with 99% alcohol. Occasionally the tabs may break off though. I had a box of these, so I was able to get several that cleaned up well.
There is a new replacement for the discontinued AB "J" types that is made by Precision Electronics and sold by CE distributing in Arizona. They're expensive though at about $24 to $34 each, but they work really well. They're audio taper in 100k, 250k and 1M ohm values.
Keep in mind that even good pots can sound scratchy it they are not isolated from DC with good blocking capacitors on both sides of the signal path.

 

[Tubetec]

Theres a friend of mine in the guitar repair trade ,
He says the only satisfactory pots he's found for instruments are the CTS kind standard on all Fender and Gibson guitars . He will offer Alphas to the cost concious but doesnt reccomend it .
He says any other Chinese pot he's ever found just wasnt right .

Ive dismantled a fair few pots over the years , In any case I prefer to take the back off ,clean ,inspect the track and wiper , rather than just dousing it down with solvents .
Even pure isopropyl can start to dissolve the carbon track on some old pots ,
On a few ocassions I found a tough electrolytic crust on either the carbon track wiper or the other metal contact ,
it caused a contact resistance of several Meg ohms .
A few times I've used a soft pencil to apply small amounts of graphite to the track , beware this will change the value to some degree , but it can improve the smoothness and quality of the contact in an old worn pot .