Source of Fender amp potentiometer

[nitenurse]

I've eventually tracked down a fault in my Fender Frontman 15R, to the Bass tone potentiometer. Here in the UK parts like that seem to be hard to find. Does anyone know of a USA source, or, failing that, would it be possible to bridge the faulty pot out altogether. At least then I would be able to use the amp.
The current pot (which I've removed), bears the number 30C250K
Thanks.
Wayne.

[J M Fahey]

Hi Wayne.
That's a hard to find (even in the USA) 250K *reverse* log curve , that´s what the "C" means.
In a pinch, replace it with an easy to get and inexpensive B250k, 16 mm pot , B meaning linear.
On "0" and on "10" it will be exactly the same as before; in intermediate positions the regulation won´t be as smooth, but nothing you won't get used to in a couple days.
Good luck.

[phatt]

Hi J M Fahey, Wayne,

AFAIK,
         That *C*would indicate an *Older type*Audio taper pot.
I don't think you can get them anymore,, probably just fender using up old stock.
Anti-log would be an *F* in the old Format,, I have no idea what they call anti-log now?

Old Code;
Lin = A
Log = C
Anti-log =F

New Code;
Lin = B
Log =A

I'm in Australia,, I don't know if other countries have different codes but there used to be a *G* and *D* taper as well. 
Yep it Can get very confusing to say the least. :duh

What is labeled a Log Audio Taper *Today* is very much different to what was sold 40 years ago. I ran into this issue while I was building my *Tone Boxes* Where it finally dawned on me that the Original HiWatt Tone stacks *Only Work* correctly with the *Older type* 500k Log pots. The new ones just don't have the magic curve shape.

BTW those 16 mm pots are quite prone to stuff up especially if they are PCB mounted.
Wanye,,, Go with JM Fahey's advice as the Frontman circuit is not Taper critical.
Phil.

[J M Fahey]

Hi Phil/Phatt
Absolutely spot-on.
Anyway, *for Fender at least*, as you stated, "A" is Log, "B" is linear, and "C" is anti-log.
In Argentina an old convention stated C1=linear, C2=log and very-difficult-to-get C3 meant anti-log, "C" meaning "curve".
Our old pot factories were local branches of USA Mallory and CTS pots, so I think that convention must have come from some of them.
The advantage of being in am industrialized Country, yet with a very small market, was that i usually can get in contact with the factory owners or managers and have special products made, in small amounts.
For example I had "S" curve pots made, the ones used in graphic equalizers, which start as log, have a middle linear section and end in antilog, in practice beind "ABC" :duh , by paying for 500 "tracks" (inexpensive) and having 100 unit lots assembled (regular price), which was very affordable.
I can also have special knobs and switches made, in 500 unit lots, and even my own sheet aluminum, in 430mmx1000mmx1.5mm size, "zero waste", since I've standardized into 430mm wide panels and chassis, I only have to cut and bend the strips needed.
Why?: because thus *any* product I make can be easily rack-mounted by adding the correct 1 inch "wings".
Now (sigh), all we have are the cheapest chinese ones.
Yes, straight PCB mount is not the best, because a hit on a pot knob or shaft, not only endangers the pot itself but the PCB also, leading even to pad or track cracks or even actual PCB itself cracks.
Anyway, production costs and competition usually mandate that simplified straight PCB mounting is used, except on expensive handmade boutique amps.
Fender pots usually have some side "wings" to help support the PCB firmly; replacing a couple of them for regular unsupported ones is acceptable, but replacing all makes for a flimsy pcb support.
Phatt: returning to PCB curves, I know that there are *two* Log curves: the "today" usual one, with 10% of resistance at mid point, called by some 10% Log and what's usually referred to as "A" curve, and what I think you refer to, the one used by old Fenders and maybe Hiwatt, the "30% Log" curve, whose "letter" I never knew.
Unfortunately, the last Argentine factory which used to accept (grumbling) my "crazy demands" such as this, closed on the 2001 crisis.
The owner and his son had been running it alone (no workforce) for the last 5 years and they tired of the endless struggle.
Oh well.
This so-called  "globalization" which really means the renaissance of slavery as a dominant economic force  is killing us all.

[nitenurse]

Thanks folks, problem resolved for the time being. Found a Fender replacement pot that was intended for a Blues Junior (tho was listed as a replacement for the BJ treble pot, not the bass that I needed. This seemed to have the same electrical characteristics so in it went and it seems fine. Then noticed that the printed circuit around the input jack was lifting away so I had to fix that as well.

Time to think about a suitable replacement I guess, I might try the Vox Pathfinder or a Night Train, I fancy a vintage Vox AC15 but doubt I could justify that to the missus! I started out with a Watkins Dominator (twin, angled front jobbie) .....sold it for £20 in 1969, now they sell for thjousands!
Thanks again,

Wayne.

[J M Fahey]

I started out with a Watkins Dominator (twin, angled front jobbie) .....sold it for £20 in 1969

:loco :loco :loco :loco :loco
:duh :duh :duh :duh :duh

Choose the correct smilie for what you feel about that 
Besides that, it doesn't matter that much for "what model" the replacement pot was intended for, only that electrical (and mechanical) characteristics match.
The good thing about finding a "Fender original" is that it also has those "reinforcement wings".

[Enzo]

Amen, a 250kC30 pot is a 250kC30 pot, regardless of what circuit they stick it in.

fender using up old stock is a quaint notion.  They made and are making endless thousands of Frontman series amps, all using the same parts.  Like most all OEM parts, they order them custom, so if they want 250kC30 pots they call Alps or whoever and order them.   They didn;t turn up in that amp because they were surplus.

[J M Fahey]

They made and are making endless thousands

of everything.
That's the point and source of many problems for us, when they want something unconventional, they can have it, and later repairs become a nightmare unless you have access to the original non-generic part.
Specially true with oriental products (which today even many "American" or "English" are). Many amps now turn up using "uPC--" or "JRC---" chips or 2SA/B/K/J--- transistors in strange packages. Oh well !!

[phatt]

Hi Phil/Phatt
Absolutely spot-on.
Anyway, *for Fender at least*, as you stated, "A" is Log, "B" is linear, and "C" is anti-log.
In Argentina an old convention stated C1=linear, C2=log and very-difficult-to-get C3 meant anti-log, "C" meaning "curve".
------
For example I had "S" curve pots made, the ones used in graphic equalizers, which start as log, have a middle linear section and end in antilog, in practice beind "ABC" :duh , by paying for 500 "tracks" (inexpensive) and having 100 unit lots assembled (regular price), which was very affordable.
------
Unfortunately, the last Argentine factory which used to accept (grumbling) my "crazy demands" such as this, closed on the 2001 crisis.
The owner and his son had been running it alone (no workforce) for the last 5 years and they tired of the endless struggle.
Oh well.
This so-called  "globalization" which really means the renaissance of slavery as a dominant economic force  is killing us all.

Wow JM Fahey, you've been around, 8|
But as you say global pressure forces us to now except second rate stuff which is very sad but not much one can do about it.

I scrounge now for old bits of electronic junk as I quite often find at least one decent component inside. As a hobby type guy I can only access what is on the shelf and the quality of such stuff is just Sad   Out of 15 NEW stomp switches I've had to replace 7 in the last 3 years due to cheap design,, yet some really old pedals made in the 60's are still working.

Cheers, Phil.

[J M Fahey]

Hi Phil. Stomp switches in particular ar terrible.
In the old times, Fender and others used "Expensive" Carling switches (I guess from $7 public to $2 or 3 OEM) now everybody uses the cheap chinese ones, which must cost less than 1 U$S .
I'm using an Argentine one(meaning second-rate in my client's minds) *plastic* single pole switch, which was made to live outdoors, supporting rain, dust, hail, whatever; the customer who ordered it makes electrical fences for cattle, and his apparatus live in the middle of nowhere without regular maintenance.
I see that "consumer grade" hardware gets worse every year, bein usually disposable, but "Industrial grade" is good, and in the long run, cheaper.
I guess consumers "buy" any b*lsh*t or snake oil that's thrown at them, and Engineers don't.