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How to identify a pot's rating?

Discussion in 'Pickups & Electronics [BG]' started by Magneto, Mar 18, 2005.

  1. How can one go about identifying a pot's rating when it has no markings on the backside?
    I'm trying to find out what size my balance pot is. The volume pot has markings.. 500k ohm.. But the balance and 3 EQ pots do not.
    Can a person use a ohmmeter, connected to the two outside lugs to find this value? If so, can this test be done while the pot is still wired, or does it have to be removed or isolated?

    Your help is greatly appreciated.. Thank you

  2. I found the markings after removing the pot. It's a B500k ohm pot.
    I was in contact with ESP guitars (This is a F204 bass with 35HZ pickups, 3-band EQ, 9volt power), and discussed an output problem that occurs when I rotate my pickup balance pot to the center position. The output at this setting is no more than half the output volume I get at either the neck and bridge pickup position.
    ESP told me that the pot should be a 250k audio taper pot, and if it's not, this could be the problem. The told me that a "slight" volume drop is normal at the center position, but the drop is much more than slight.

    Any thoughts about this? They told me to let them know if I need them to mail me the part.

  3. Ed Fuqua

    Ed Fuqua

    Dec 13, 1999
    Augusta GA
    Chuck Sher publishes my book, WALKING BASSICS:The Fundamentals of Jazz Bass Playing.
    The only two ratings I'm aware of are "skunk" and "killer".
  4. It sounds like you've just been spoiled on the good stuff.. Down here in South Texas... need I say more? :)
  5. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    That sure sounds like an out-of-phase problem, no? Are the pickup leads reversible on that bass?
  6. SirPoonga


    Jan 18, 2005
    You can do it while it is plugged in. You actually test and outside lug to the middle lug. Completely rotated one way one outside lug will read 500k, other 0k. Turn knob other way completely and values are reversed.

    Blend pots are usually linear, which is what the B500K suggests. Audio taper you usually see A500 on the pot. Since the purpose of a belnd pot is to smoothly transition form one outside lug to the other. Audio taper is a logrithmic scale so it isn't balanced in the middle.
  7. Thanks for the replies and the information. I'll read it over carefully. I had another thread awhile back about this output drop anomoly.. <-- hope I spelled that right!

    These are stock electronics on a bass that's about a year old..
    I'm sure the wiring and potentiometer values are particular to my given electronics. Most of the blend pots I've seen are the dual layer type. The one in my bass doesn't appear to be..
    I have a B500k pot for volume, and it's larger than the B500k for the pickup blend/balance.
    It was always bugging me that the center position output was so low compared to both full-bridge/full-neck pup output.
    I emailed ESP about this, and was told that the blend pot was supposed to be a 250KA (audio taper) pot, and if it isn't, this could be the problem.
    I wrote back to ESP, and I guess I'll wait to hear from them, as they aren't easy to get in touch with over the phone.
    Although I wouldn't think that the wrong pot could have been installed at the factory, it's always possible.

    I wonder if anyone could suggest what I could expect by changing from the B500k to a 250KA. I read another post here at this forum about a B500k actually being an audio tapered pot..

    Thanks again for helping..

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