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  1. #1
    Les Paul Forum Member Highway Star's Avatar
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    Potentiometers measures way to high

    I have a question I hope you skilled vintage Les Paulers can help me out with . The original pots in my 1955 les paul measures way to high. Is this common and if so, what is the reason for that?

    V1=670
    V2=1,53
    T1=846
    T2=1,69

  2. #2

    Re: Potentiometers measures way to high

    The values you give aren't clear. Is 1.53 1.53meg? Did you un solder your pickups to test values? I've had lots of '50s pots that test way above the 500k range. Some say it's because of years of use but I think that were just made way off spec. High value volume pot makes the pickup sound brighter and more open. Great for a neck pickup but not so great for a bridge pickup

  3. #3
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by zappa1777 View Post
    The values you give aren't clear. Is 1.53 1.53meg? Did you un solder your pickups to test values? I've had lots of '50s pots that test way above the 500k range. Some say it's because of years of use but I think that were just made way off spec. High value volume pot makes the pickup sound brighter and more open. Great for a neck pickup but not so great for a bridge pickup
    Thanks for your reply. The pots are un-soldered from the guitar. I chosed to use other pots from the 80's instead because of the values. But maybe the V2 on the neck pickup would sound great .

    Sorry, about not clarifying the values. I don't know where to find the ohm sign on the keyboard but here it goes:

    V1= 670 Kohm
    V2= 1,53 Mohm
    T1= 846 Kohm
    T2=1,69 Mohm

  4. #4
    Les Paul Forum Co-Owner Tom Wittrock's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by Highway Star View Post
    Thanks for your reply. The pots are un-soldered from the guitar. I chosed to use other pots from the 80's instead because of the values.
    You changed them because of ohm readings?
    How did the sound before you changed them?
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  5. #5
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by Tom Wittrock View Post
    You changed them because of ohm readings?
    How did the sound before you changed them?
    The pots were changed in the 80's. I just got the original ones in a plastic bag when I purchased the guitar. My intention was to install the original ones yesterday but I chosed not to because of the ohm values.

  6. #6
    Les Paul Forum Member KR1's Avatar
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    Re: Potentiometers measures way to high

    Wild guess from the sidelines here but I think those pots need a thorough spray cleaning followed by a blowout with compressed air. Unless you’ve already done this, I think your measurements will settle down a bit. Also, if the pickups read in the 7.x range, they will sound fine with the cleaner pots.

    (Assumption: Centralab pots, all original, no damage)

  7. #7
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    I'll attach some pics to make sure these are legit etc.

    Attachment 6835

    Attachment 6836

    Attachment 6837

  8. #8
    Les Paul Forum Member renderit's Avatar
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    Re: Potentiometers measures way to high

    Nope. The cap looks to maybe be ok (possibly a remake though, have to check letter style) but the pots are junk.


  9. #9
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by renderit View Post
    Nope. The cap looks to maybe be ok (possibly a remake though, have to check letter style) but the pots are junk.
    Hmm, do you mean that 50's LP pots in general are junk och these specific ?

  10. #10
    Les Paul Forum Member KR1's Avatar
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    Re: Potentiometers measures way to high

    .
    Last edited by KR1; 01-14-18 at 10:37 AM.

  11. #11
    Les Paul Forum Member KR1's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by Highway Star View Post
    Hmm, do you mean that 50's LP pots in general are junk och these specific ?
    The original spec Centralab pots were fine. Those arenít original spec, so my assumptions, above, arenít valid.

  12. #12
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    So what you are saying is that the pots are IRC copies or ripp offs?

    EDIT: I would be very suprised if that was the case. The pot dates 449 (1954 w 49) fits with the rest of the guitar and it has a good provenance.
    Last edited by Highway Star; 01-14-18 at 12:18 PM.

  13. #13
    Les Paul Forum Member KR1's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by Highway Star View Post
    So what you are saying is that the pots are IRC copies or ripp offs?

    EDIT: I would be very suprised if that was the case. The pot dates 449 (1954 w 49) fits with the rest of the guitar and it has a good provenance.
    Edit: I see your pot photo now..

    I haven't encountered IRC pots in vintage Pauls. There are others here more qualified than me to make the assessment, but I am unaware of any pot manufacturer other than Centralab or CTS (rare) being used as original suppliers to Gibson for these guitars. This plus the ohm ratings would cause me to doubt the originality of these parts for your guitar.
    Last edited by KR1; 01-14-18 at 02:51 PM.

  14. #14
    All Access/Backstage Pass Wilko's Avatar
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    Re: Potentiometers measures way to high

    I'm thinking it more likely that the meter isn't working, or isn't being used/read properly.

    Those measurements just don't make sense and are not common for these simple parts. Even with the errors in your listing the values, it seems like you're not too sure about it.

    Just in case, here's some help: http://www.instructables.com/id/How-...Potentiometer/

  15. #15
    Les Paul Forum Member KR1's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by KR1 View Post
    Edit: I see your pot photo now..

    I haven't encountered IRC pots in vintage Pauls. There are others here more qualified than me to make the assessment, but I am unaware of any pot manufacturer other than Centralab or CTS (rare) being used as original suppliers to Gibson for these guitars. This plus the ohm ratings would cause me to doubt the originality of these parts for your guitar.

    Sorry to quote myself, above, but after I posted that I had this hazy memory of "IRC" coming from somewhere. In any case, one other researcher (link below) does list IRC as a supplier to Gibson in the 50's, specifically in the Les Paul range. Perhaps more importantly, this same contributor correctly deciphers the IRC serial numbers which have an entirely different format than the other common suppliers. So, notwithstanding the strange ohm readings you are getting (might not be correct), you have to read ALL of the numbers on those pots in order to get the year of manufacturer. In the example given at the link below, an IRC number would be deciphered:

    6154190: 615 = IRC, 4190 is the part number, not the date code
    the resistance value follows (i.e. 500)
    the year/month is last, (i.e. 543 = 43rd week of 1955)

    See this: http://www.guitarhq.com/pots.html#irc

    Don't throw anything away yet!

  16. #16
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by KR1 View Post
    Sorry to quote myself, above, but after I posted that I had this hazy memory of "IRC" coming from somewhere. In any case, one other researcher (link below) does list IRC as a supplier to Gibson in the 50's, specifically in the Les Paul range. Perhaps more importantly, this same contributor correctly deciphers the IRC serial numbers which have an entirely different format than the other common suppliers. So, notwithstanding the strange ohm readings you are getting (might not be correct), you have to read ALL of the numbers on those pots in order to get the year of manufacturer. In the example given at the link below, an IRC number would be deciphered:

    6154190: 615 = IRC, 4190 is the part number, not the date code
    the resistance value follows (i.e. 500)
    the year/month is last, (i.e. 543 = 43rd week of 1955)

    See this: http://www.guitarhq.com/pots.html#irc

    Don't throw anything away yet!
    It's funny. I just visited that webpage and read that exact info before ending up here again. It fits my pots perfectly. I got the same number on my pots exept the three last digits .

    Copy pasted the info:

    IRC Pots (as used on many Gibson Les Pauls).


    • IRC (International Resistive Company) used a different source-date code system. For example, here's a typical 1950s IRC code seen on a 1955 Les Paul Junior pot: 6154190 500k 543
      ^^^----------------- 615 is the source code for IRC
      ^^^^------------- 4190 is IRC part# (0689 & 2632 also common)
      ^^^^-------- 500k is the pot value in ohms
      ^------ last year's digit (0 t0 9), hence 1955
      ^^---- week (01 to 52), hence 43rd week

  17. #17
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by Wilko View Post
    I'm thinking it more likely that the meter isn't working, or isn't being used/read properly.

    Those measurements just don't make sense and are not common for these simple parts. Even with the errors in your listing the values, it seems like you're not too sure about it.

    Just in case, here's some help: http://www.instructables.com/id/How-...Potentiometer/
    Thanks. The guys in the store where I bought it measured the pots. I'll think it is accurate to control the results considering this discussion.

  18. #18
    Les Paul Forum Member KR1's Avatar
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    Re: Potentiometers measures way to high

    Sorry for the bad initial data.

    F around with those resistance readings a bit more. Iím back to the notion that a good cleaning and re-read might have you back in the normal range on those IRCís.

    So what is the year/month date on them?

  19. #19
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by KR1 View Post
    Sorry for the bad initial data.

    F around with those resistance readings a bit more. Iím back to the notion that a good cleaning and re-read might have you back in the normal range on those IRCís.

    So what is the year/month date on them?
    No problem, thank God for the internet . I'll re-read and probably a good spring clean will come up soon

    The pots date code is 449 which is 1954 week 49.

  20. #20
    Les Paul Forum Member KR1's Avatar
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    Re: Potentiometers measures way to high

    Excellent-

  21. #21
    Les Paul Forum Member JJ Blair's Avatar
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    Re: Potentiometers measures way to high

    The pots can't be measured properly in circuit. Also, you'd have to disconnect the wiper from the ground. I think this is why your readings are whack. Somebody at the shop doesn't know shit about electronics.

  22. #22
    Les Paul Forum Member renderit's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by Highway Star View Post
    Hmm, do you mean that 50's LP pots in general are junk och these specific ?
    I could be wrong. But I have never seen that type in an LP. Maybe someone else will chime in here who knows more. I used a bunch of those in the 70's. I don't think the plastics on them were even around in the 50's. They were crap compared to the stock ones. That said, I AM NOT AN EXPERT. But that type NEVER impressed me.


  23. #23
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by renderit View Post
    I could be wrong. But I have never seen that type in an LP. Maybe someone else will chime in here who knows more. I used a bunch of those in the 70's. I don't think the plastics on them were even around in the 50's. They were crap compared to the stock ones. That said, I AM NOT AN EXPERT. But that type NEVER impressed me.
    Maybe the 70's pots differ from the ones made in the 50's in quality?

    Anyway, guitarhq says the opposite. That IRC pots are very common in les pauls from the 50's. Mine got the exact same number as his example exept the date.

    http://www.guitarhq.com/pots.html#irc

    EDIT: This 1955 pot is up for sale. Looks exacly like the ones I got and same number exept date code:

    http://www.cathedralguitar.com/Aucti...500k/500k.html



    Last edited by Highway Star; 01-15-18 at 10:48 AM.

  24. #24
    Les Paul Forum Member Highway Star's Avatar
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    Re: Potentiometers measures way to high

    Quote Originally Posted by JJ Blair View Post
    The pots can't be measured properly in circuit. Also, you'd have to disconnect the wiper from the ground. I think this is why your readings are whack. Somebody at the shop doesn't know shit about electronics.
    Thanks for your input. I'll measure them myself to double check

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