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Topic: Volume Pot ID wanted! |
Larry Chung
From:
San Francisco, CA, USA
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Posted 21 Apr 2003 2:45 pm |
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I just found some old Allen Bradley pots for cheap and wanted to know if they are suitable for use with a steel volume pedal.
They all read:
"AB
62019B
U-500K-Ohm
TYPE-J"
Any ideas about the coding?
Thanks in advance! |
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John Bechtel
From:
Nashville, Tennessee, R.I.P.
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William Peters
From:
Effort, Pennsylvania, USA
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Posted 22 Apr 2003 4:02 am
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Larry,
I think the designator is not for the extended life version (Type EJ) though, so they may not last very long.
Bill
Cougar SD-10 |
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Blake Hawkins
From:
Florida
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Posted 22 Apr 2003 6:39 am
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I believe that the "U" on the pot indicates a "linear" taper.
In which case they would not be suitable for use in a foot volume pedal.
Blake |
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John Bechtel
From:
Nashville, Tennessee, R.I.P.
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John Bechtel
From:
Nashville, Tennessee, R.I.P.
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Bill Crook
From:
Goodlettsville, TN , Spending my kid's inheritance
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Posted 23 Apr 2003 5:01 am
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I thought a "linear" taper was what we needed.....
That way, the volumne would be consistancely increased throught-out the range of the pot.
Useing an "Audio-taper" pot, the first ½ of the pot has the most active action. The 2nd half,really dosen't do too much.
The "Audio-taper" pot was designed for the radio receiver because:
1) The consumer wanted a volumne control that was most effective at relative low volumne.
2) At the upper end of the pot,one is subjected to distortion and break-up of the signal.
So, what we want is for the signal level to be linear throught the travel, not logarithmtic with-in the first ½ of the travel of the pot.
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John Lacey
From:
Black Diamond, Alberta, Canada
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Posted 23 Apr 2003 5:18 am
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| I think that the log taper goes the other way, just like on a graph, low at the start and increasing rate of volume near the end of the travel. It'd be great if someone would find a couple hundred of those AB pots in NOS condition that us volume pedal pot owners could use as an alternative to the shitty Dullostats. |
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Bill Terry
From:
Bastrop, TX
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Posted 23 Apr 2003 6:22 am
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| I thought audio taper was used because of the non-linear nature of audio signal levels? e.g. it's measured in dB, a log scale, you have to double the power to get 3dB more gain, a very non-linear relationship. |
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Michael Brebes
From:
Northridge CA
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Posted 23 Apr 2003 6:22 am
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| You want audio taper because the ear hears sound levels logrythmically, not linearly. Better macke sure they are audio taper. If you can physically check them with an ohm-meter, with the wiper in approximate center, the resistance between the wiper and any other leg should be roughly 250K. Audio taper would have a much different measured value. Unfortunately Allen Bradley doesn't exist anymore so finding out the numbering scheme is a bit difficult. |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 23 Apr 2003 7:23 am
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A "U" generally designates a linear taper, and as Michael said, this is not suitable for use as a volume control. As to the "extended life" pots, they are a modern version of the old Type J pots, and offer no benefits, as they are made to exactly the same Mil-Specs. I know how good the old ones work, so that's what I use! I recommend JA1N200P504AA, which should last for several years. Don't accept (or try) a substitute, and you probably won't be disappointed.
In addition, it is beneficial to oil the pots before installing them, as some of the "noise" complaints come from wear at the bushing/shaft juncture. |
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John Bresler R.I.P.
From:
Thornton, Colorado
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Posted 23 Apr 2003 7:44 am
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In "Steel Guitarist" magazine No. 1, page 18, Greg Lasser wrote an article on easing a volume pot. He specifically states it should be an Allen Bradley Type J and be an Audio Taper. He doesn't post the numbering scheme, however.
Maybe those who used to order and sell them would know the original numbering scheme, like Tom Bradshaw or Scotty. |
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Fred Shannon
From:
Rocking "S" Ranch, Comancheria, Texas, R.I.P.
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Posted 23 Apr 2003 7:57 am
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[This message was edited by Fred Shannon on 06 December 2004 at 02:24 AM.] |
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Robert Parent
From:
Gillette, WY
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Posted 23 Apr 2003 9:39 am
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Several years ago I did a little research on the AB pot and from what I remember found that it was neither a true linear or audio taper. It was the taper issue that caused the various suppliers I talked with a problem in having a direct cross reference.
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Gene Jones
From:
Oklahoma City, OK USA, (deceased)
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Posted 23 Apr 2003 10:00 am
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| Since the demise of the Allan Bradley, I have had success with the "Clarostat 500k-ohm 9226,extra life Mexico". I have one on a Sho-Bud pedal that has been there since 1994. www.genejones.com |
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Larry Chung
From:
San Francisco, CA, USA
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Posted 23 Apr 2003 11:11 am
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Thanks, everyone, for the replies. I plugged one of them in last night and found that the volume "came up" very quickly and had little effect through the last 20-30% of rotation/travel.
Linear, yes?
Waah.
(: |
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Bruce Derr
From:
Lee, New Hampshire, USA
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Posted 30 Apr 2003 7:08 pm
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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. As you can see, there are many variations that could be acceptable for volume pedal use. I hope this helps someone find some usable bargain pots somewhere. |
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