Wrong pot type?

Steel guitar amplifiers, effects, etc.

Moderator: Shoshanah Marohn

Post Reply
User avatar
Ken Byng
Posts: 4313
Joined: 19 Feb 2001 1:01 am
Location: Southampton, England

Wrong pot type?

Post by Ken Byng »

I thought I was getting a bargain when I had the chance to buy 10 Allen Bradley new-old stock JAIN048S501UA TYPE J 500k pots for $5.00. Now I have a sneaky suspicion that they are linear and not log. Anyone tell me if I have a bargain or a boo boo?
Michael Whitley
Posts: 50
Joined: 4 Feb 2005 1:01 am
Location: Oxford, Mississippi, USA

Post by Michael Whitley »

Well, you've got two letter A's in the part number, and no L's. I'd say that's a good sign.
User avatar
John Daugherty
Posts: 2188
Joined: 13 May 2004 12:01 am
Location: Rolla, Missouri, USA
Contact:

Post by John Daugherty »

Ken, you could measure the resistance between an end terminal and the center terminal of the pot while set at 50% of its rotation. If it measures 250K ohms it is linear.
Donny Hinson
Posts: 21192
Joined: 16 Feb 1999 1:01 am
Location: Glen Burnie, Md. U.S.A.

Post by Donny Hinson »

Uhhh...sorry. "UA" is linear taper, "AA" is audio (log) taper.

Here's some info that was posted awhile back...

Explanation of AB Type J part numbers, to aid in identification of surplus pots:
Example from above post: JA1N200P504AA

JA = Single section type J
(JS = single with switch, JD = dual, JB = dual with switch, JE = triple)

1 = Standard locating lug location
Facing the shaft, with solder lugs at bottom:
1 = Lug at 9 o'clock
2 = Lugs at 9 and 3 o'clock
3 = Lug at 3 o'clock
4 = No lugs

N = Plain bushing, 0.375" long
(Other options are for different bushing lengths, locking bushings, watertight bushings, etc.)

200 = Shaft length in inches (2) and 64ths (00)
056 would be 56/64" (7/8")

P = Plain round shaft ending
(S = slotted, F = flatted)

504 = Resistance 500,000 ohms (500k)
(The 4 indicates the number of zeros following the first two numbers. 254 is 250k; 105 is 1 meg.)

AA = The first A indicates taper and tolerance:
A = Clockwise modified logarithmic, +/-10%
R = Clockwise modified logarithmic, +/-20%
B = CounterCW modified logarithmic, +/-10%
T = CounterCW modified logarithmic, +/-20%
D = Clockwise exact logarithmic, +/-10%
K = Clockwise exact logarithmic, +/-20%
U, M, S, Y, C, and F are linear tapers

The last A just indicates what mounting hardware comes with the pot.
A = one mounting nut and one lockwasher

This info is from the 1981 AB catalog.
(Thanks to Bruce Derr)
User avatar
Jack Stoner
Posts: 22087
Joined: 3 Dec 1999 1:01 am
Location: Kansas City, MO

Post by Jack Stoner »

A "U" taper is a linear taper.
I can't find anything on a "UA" but I suspect it's some type of modified linear taper since the "AA" type, which is what the "real" Allen Bradley's were indicated a modified analog taper.
Roger Kelly
Posts: 2960
Joined: 4 Aug 1998 11:00 pm
Location: Bristol,Tennessee

Post by Roger Kelly »

Check your part number with this one. You may not be getting the right one?

Image
Tommy Roten
Posts: 136
Joined: 7 Jul 2004 12:01 am
Location: Trondheim, Norway
Contact:

Post by Tommy Roten »

I found some cheap pots on a site, and the info is this: LOG potmeter, RV4SAYSD504C mil code, 1.2 cm high, 2.8 cm diameter. Are they any good?

------------------
Franklin D-10, MSA D-10, Goodrich volped, Mesa Boogie Quad preamp, ProfexII, Mosvalve 1500, 2xEminence 12", Nashville 400,
www.tommy-steel.com
pertrot@frisurf.no


User avatar
Ken Byng
Posts: 4313
Joined: 19 Feb 2001 1:01 am
Location: Southampton, England

Post by Ken Byng »

I'm getting the pots from the dreaded auction site - should have done my homework first. The serial number is correct - they have posted a photo of it.

KB
Glenn Suchan
Posts: 2351
Joined: 24 Sep 1998 12:01 am
Location: Austin, Texas

Post by Glenn Suchan »

Ken,

It's NOT the-end-of-the-world if you already have the pots. I've used the linear pot in volume pedals and I'll say this before donning the flame-retardant gear: They work fine. The first time I used one, it was the result of a mistaken purchase. I didn't realize there were audio tapers on pots. I thought all were linear. That being said, I hardly noticed the difference playing. Pedal movement is more critical, but if you're like me and use the volume pedal mainly for note sustaining, you'll find linear pots will help to keep you from swelling your volume too much.

Linear taper pots may not be everyone's "cup of tea", but I have an Emmons pedal and a Goodrich pedal with audio tapered pots and a Goodrich pedal with a linear taper pot and I have no problem switching among them.

Keep on pickin'!
Glenn
User avatar
Bob Snelgrove
Posts: 3208
Joined: 4 Aug 1998 11:00 pm
Location: san jose, ca

Post by Bob Snelgrove »

Jason Hull
Posts: 553
Joined: 16 Jan 2010 9:05 am

Post by Jason Hull »

A linear pot can actually be better than an anolog pot, with the addition of a resistor. Check out this link:

http://sound.westhost.com/project01.htm
Post Reply