The Steel Guitar Forum

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?

Well, you've got two letter A's in the part number, and no L's. I'd say that's a good sign.

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.

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)

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.

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

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

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

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

Any of these what we need? :

http://www.surplussales.com/Potentiomet ... ed-10.html


bob

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