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potentiometers for PCB FEnder tube amps

Wally
December 10th, 2010, 12:46 PM
I am in a bind. I am looking for a mid tone control pot for a Fender Super 60.
Can anyone help with this search. FEnder doesn't stock the part, and it seems that the parts were proprietary---made for FEnder----. That means that these pots are no longer available. Teh pot is a 25K10A pcb mount pot with a D shaft. I could probably work with anything form 15K-50KA.
I got a response from a well-known tube amp parts resource yesterday...

"Wally,

sorry, I do not have any replacement parts for the Super 60. they are proprietary (made for Fender) and no standard parts will fit. having the "D" shaped shaft doesn't make it any easier too.

I have a 25k mini pot, but it is not circuit board mounted and has a round shaft - not a very close fit.

and yes, Fender left us all out in the cold not providing parts for current vintage amps. They made this decision in the mid 90's - now they don't even know what you are talking about.

this is about the 5th request today for Fender parts.

I had bought out a lot of the guys who did have parts some years ago, but 100% of that stuff is gone."

This response is simular to the ones I got from Darren Riley and Angela INstruments.....no such potentiometer to be had. I ran into this problem with a swtiching pot in a The Twin some years ago....I had to rebuild the switch mechanism with new parts from a new pot...tore the new one up to get those switching parts.
If anyone has any cures for this predicament, I would appreciate the help. PErhaps a mini-pot that doesn't mount to the board could be hard-wired in????
Imho, this certainly diminishes any thoughts I might have about buying any of the FEnder PCB amps from that period---mid-80's through the '90's....unless they were in working condition and the price was very low. And.....if Fender holds true to this method of building amps, when will the parts for the current production no longer be available....or are they using commonly available PCB-mount parts these days?

When I took that The TWin in for work about 10 years ago, the owner said..."Now, you'll be able to get this fixed quickly because it is a newer amp, right? I smiled and said: "IF you had brought me a BF TR, I could have it going tomorrow. With this one, I have no idea when I can get the parts. AFter waiting 6 months for fEnder to respond--through a fender dealer---I rebuilt the swtiching mechanism. THat amp is still going. However, if it had been anything except the switch mechanism that was broken, that pot would be an empty hole......unless someone of you knows where to get these unobtainable pots?????

ANy help is appreciated.

Jeff B.
December 10th, 2010, 01:00 PM
Antique Electronic Supply (www.tubesandmore.com) may have something. They have some Fender PCB mounted "D" pots in their catelogue.
Go to page 54 of their online catelogue.

You don't need to use a PCB mounted pot. Just run wires to the corresponding contacts on the pots terminals. You can just file a flat spot on the pot for a "D" as long as the shaft size is correct for the knob. Protect the pot from the filings.

If you can only find a larger pot value it is possible to lower it's value be adding a resistor across it's terminals. It will alter the taper a bit.

Wally
December 10th, 2010, 01:18 PM
Thanks, JEff.....all of those options I have considered. AES has no direct replacements. I have the CE Distribution catalog...whoelsale arm of AES....and they have nothing that is remotely applicable unless I can squeeze a larger pot into that small space afforded by the PCB cosntruction....and that is a tight space under that front panel PCB. I dont' have the amp in hand yet to know exactly what will or will not fit. I am looking for a mini-pot. I suppose 25KA pot such as used with active pickup circuits will have to do???
IT is frustrating to have to spend $30 worth of time modifying a $5 pot to fit an amp that is 15 years old....when I routinely repair amps that are 30-60years old with parts I have on hand, right?

Maybe I am simply venting, eh? I do know that for the fellow who just bought this amp...and he buys a lot of vintage/used equipment....the price/value of this type of amp just went WAY down. For me, it simply reinforces what I already knew....I don't want this type of amp regardless of how it might sound.
AS Chuck Berry sang....
"Too much monkey business,
Too much monkey business.
Too much monkey business
for me to be involved in."

Timbertea
December 10th, 2010, 01:48 PM
You might try Element14, Wally. It occurred to me that they were suppliers for Yamaha parts, and probably have something in a D style pot board mount as they have to support the Yamaha amps. http://us.element-14.com/

Wally
December 10th, 2010, 01:50 PM
Thanks, Timbertea, I'll try anything at this point.

celeste
December 10th, 2010, 08:49 PM
If you find something Wally, can let me know? I have a Princeton DSP here that had something dropped on its face and sheared all the pots off.

Billm
December 10th, 2010, 08:58 PM
Do you have a gut shot of the pot? Some dimensions, especially pin spacing and distance from the pins to the end of the shaft? I have been through a fair number of pots looking for BJr-compatible, non-Fender parts, and maybe one of them will work.

And if you're really desperate, I've also had experience wiring panel-mount pots to the PCB. You typically don't have much room to work, but it's doable.

strat56
December 10th, 2010, 09:33 PM
Deleted

kec!
December 11th, 2010, 10:54 AM
Any pics Wally?

Does it look like any of these?...

http://img.photobucket.com/albums/v521/kecline/Amps/pot1.gif

http://img.photobucket.com/albums/v521/kecline/Amps/pot2.jpg

http://img.photobucket.com/albums/v521/kecline/Amps/pot3.gif

Wally
December 11th, 2010, 12:17 PM
Celeste, I certainly will let everyone know if I find some direct replacement parts for these applications.
BillM, I don't have the amp on my bench, so I don't have measurements of the spacing for the lugs/tabs. I do have pictures. The amp is in New MExico waiting to make the trip over here.
Kec, the pots in these amp do not have the stand off mounting tabs. IT might be that that mounting bracket could be removed??? Where can one find that pot you show there?
Thanks to all for the time and responses. IT is a pity that Fender doesn't see fit to support these products with parts service, isn't it? The owner of this Super 60 likes the amp...but he is greatly perturbed by this parts dilemna. IF say a car maker didn't provide parts support for their product, that would be the end of that car company, right? OH well....on to work....

kec!
December 11th, 2010, 01:46 PM
Wally,

Found them on eBay. They are however 50k.

Not sure if these are log or linear...

http://cgi.ebay.com/NEW-Genuine-Fender-50K-30C-PCB-Amp-Potentiometer-Pot-/200553675029?pt=LH_DefaultDomain_0&hash=item2eb1ee3915

http://cgi.ebay.com/NEW-Genuine-Fender-50K-15A-PCB-Amp-Potentiometer-Pot-/200542888932?pt=LH_DefaultDomain_0&hash=item2eb149a3e4

This one is linear. I think you need log.

http://cgi.ebay.com/Fender-Blues-Jr-50k-linear-Reverb-Master-potentiometer-/150471327768?pt=LH_DefaultDomain_0&hash=item2308ca4018

kec!
December 11th, 2010, 02:02 PM
Also check Mouser - see links. I narrowed it down for you :smile:

http://www.mouser.com/Catalog/catalogusd/642/685.Pdf
http://www.mouser.com/Catalog/catalogusd/642/684.Pdf
http://www.mouser.com/Catalog/catalogusd/642/689.Pdf

As Bill suggested, you may have to wire it manually :cry:

Wally
December 11th, 2010, 03:03 PM
kec!, thanks for your time and diligence. The ebay seller has a 50K15A snapin pot that might do after removing the mounting frame. Mouser might have a 50KA that will be simpler. They don't have any 25KA, though.
I appreciate your digging,kac! AS a side benefit, your last link took me to some slide potentiometers that I need study to see if anything works for an old Silvertone P.A. unit that is sitting here.
Thanks to all for the help, and I will let ya'll know how things transpire and what cures this problem.

kec!
December 11th, 2010, 03:47 PM
Glad I could help Wally.

Mouser also started carrying Bourns pots for guitars...

http://www.mouser.com/Catalog/catalogusd/642/690.Pdf
http://www.mouser.com/Catalog/catalogusd/642/691.Pdf

tap4154
December 11th, 2010, 06:45 PM
According to the service diagram that came with my Super 210 the pots are all different values.

Main volume: 250K 10A (push/pull on the 112 and 210)

Treble: 250K 30A

Mid: 25K 10A

Bass: 250K 10A

Gain (listed as Ra and Rb -- stacked?): 1 Meg 10A

Dist Volume: 1 Meg 10A

Reverb: 5K

Presence: no value listed.

ojaverde
December 12th, 2010, 12:16 PM
I have a couple of these pots that I don't need, but they are 250k. Right size, wrong value. Isn't a pot just a variable resistor? Is there a way to add a resistor or cap to change the value?

tap4154
December 12th, 2010, 12:23 PM
I have a couple of these pots that I don't need, but they are 250k. Right size, wrong value. Isn't a pot just a variable resistor? Is there a way to add a resistor or cap to change the value?

Yes, and I'm assuming the OP is probably aware of this:

http://www.projectguitar.com/tut/potm.htm

However, I'm not sure how far down you can tweak a pot, what it does to the taper, or if it has any other adverse effects. I would imagine using the correct value pot would always be better (?)

Wally
December 14th, 2010, 04:55 PM
Okay, here's an interesting situation. I have found a possible source for NOS Fender-sourced pots for this era, but I need parts numbers. Does anyoone have a parts list for these amps??? Fender not only won't maintain parts availability, but they won't share the parts numbers, either. My googlin' hasn't brought the parts # info to the surface yet.

InyoTim
December 14th, 2010, 06:13 PM
I remember contacting Fender for an optocoupler for a Twin II years ago. They told me to take the amp to an authorized Fender repair shop. Fender not sharing the part numbers with you is probably more of this.

Wally
December 14th, 2010, 06:18 PM
INyoTim, I just talked to a fEnder authorized service center, and he didn't have the parts numbers either. IMHO, there is noreason for FEnder to 'protect' their service centers....because FEnder doesn't have these parts, anyway! Tehy dropped the support long ago on these amps.

tap4154
December 14th, 2010, 06:38 PM
I found a 50K PCB pot with D shaft (but no 25K).

Fender part # 0027943000

Almost halfway down on this page:

http://www.darrenriley.com/FenderAmpParts.htm

InyoTim
December 14th, 2010, 06:40 PM
I have found a possible source for NOS Fender-sourced pots for this era, but I need parts numbers.

Wally, is this your source for parts? http://www.musicpartsguru.com/
The thread where I found this link mentioned part numbers being printed on the pot. I assume there is no number on the pots you are wanting to replace?

Wally
December 14th, 2010, 07:16 PM
I found a 50K PCB pot with D shaft (but no 25K).

Fender part # 0027943000

Almost halfway down on this page:

http://www.darrenriley.com/FenderAmpParts.htm

YEs, I checked with Darren as my first option. Part number 0027940000 is a closer fit....and I may go that route. (The 0027943000 pot doesn't specify the taper.) The bracket will have to be removed somehow to fit since these older amps did not have the snap in bracket. Mouser gets even closer with a pot that doesn't have that bracket. But....noone has a 25KA pot. I have a lead on some NOS parts form the era....but I need the FEnder part number.?.?
INyoTim, I too have read that the part number is on the pot. This search is compounded in that the part is still in the board, and the board is 110 miles away. AS I type, the owner is attempting to fidn that number.....or remove the pot. His situation is compounded by the fact that he pot still 'works'...that is, the amp is operative. HE simply broke the shaft trying to straighten it....after I told him to leave it alone, right? LOL