The Fender Forum
NEW! LPF Facebook Page
NEW! LPF Instagram Page
Merchandise & Donations
NEW! Burst Serial Log Home Page
LPF Homesite
Results 1 to 14 of 14
  1. #1
    Les Paul Forum Member thin sissy's Avatar
    Join Date
    Jan 2006
    Location
    Sweden
    Posts
    2,431

    50's pots and high resistances. How do they affect tone?

    I have a 55 GT that had replacement pots in it when I bought it. The original (IRC, not Centralabs) came in a bag with the guitar. The original measure the following resistances in rising order:

    670 kOhm
    846 kOhm
    1,48 MOhm
    1,69 MOhm

    I assumed they were switched out because of their high readings. So with nothing to lose, I opened up the one with the highest resistance and cleaned the carbon tracks with isopropanol and then lubed it with a hint of fader lube. The resistance is still as high as it was before. So I thought "that's that, the carbon track is worn out I guess".

    But I asked the original owner who told me the pots were switched out due to experimental lust in the 70's, not because the old ones were bad. Also the tone pots were practically never used for 40 years according to him, yet they had the high resistance readings.

    So it turns out I couldn't "fix" the resistances by cleaning the pots. They all look to be in great shape though. I wonder two things:

    - Could IRC pots from 1954 vary this much from the start? If not, why would they have risen so much in resistance?

    - More importantly, could I use any of these pots again? And what would the effects be? I'm thinking I could put the 670 kOhm one on the neck volume at least? Or maybe I could even use the 846 kOhm one too, and put that one on the neck volume and the 670 on the bridge volume? But are these resistances too high you think?

    I've heard about old pots sometimes reading much higher than 500 kOhm. I do like a bright neck pickup
    This is a song from the new album, it's a deep meaningful song this one... No, it's not whiskey in the fucking jar... Philip Lynott

  2. #2
    Les Paul Forum Member Hamerfan's Avatar
    Join Date
    Dec 2004
    Location
    From the best part of Germany - Bavaria
    Posts
    714

    Re: 50's pots and high resistances. How do they affect tone?

    Yes pots can vary that much. Even today you can pot with +/- 20% tolerance. That means 800k to 1200k on a nominal 1 meg pot. Use them!
    The rule of thumb say: The lowest reading as bridge volume, the highest as neck volume (to retain the highs) and the other 2 as tone pots.
    BTW the hearing is not linear like the readings. You will hear more difference between the lower ones than between the higher ones.

  3. #3
    Les Paul Forum Member thin sissy's Avatar
    Join Date
    Jan 2006
    Location
    Sweden
    Posts
    2,431

    Re: 50's pots and high resistances. How do they affect tone?

    Hmm, very interesting . I now think I wont open up the remaining three pots. I'll probably just spray them from the outside. But is it really possible that two of the pots were manufactured with values well over 1 MOhm?

    I'm seriously considering putting the two lowest reading pots back in the volume spots! How would tone pots with very high readings affect the tone though? I might not use the two of them if it's too drastic. I bought a set of VIPots last year, might use two of them for the tone positions.
    This is a song from the new album, it's a deep meaningful song this one... No, it's not whiskey in the fucking jar... Philip Lynott

  4. #4
    Les Paul Forum Member Hamerfan's Avatar
    Join Date
    Dec 2004
    Location
    From the best part of Germany - Bavaria
    Posts
    714

    Re: 50's pots and high resistances. How do they affect tone?

    I would use them all. A higher resistance preserves the highs and open up the sound, if you use them as Volumes. On the neck they de-mud the lows and give a little bit more volume. On the bridge volume it could a bit brittle, so there you should use the lowest reading. On the tone pots it doesn't matter that much what resistance you have as long its higher than 500k.
    The tolerances on electronic parts are usally high. With caps i have seen over 100% in both directions - okay they are drifting over the decades more than pot probably.
    Use it like i said in my former answer.

  5. #5
    Les Paul Forum Member
    Join Date
    Jun 2007
    Location
    England
    Posts
    476

    Re: 50's pots and high resistances. How do they affect tone?

    Quote Originally Posted by thin sissy View Post
    But is it really possible that two of the pots were manufactured with values well over 1 MOhm?.
    No, if they are 500K pots then the value when they were manufactured would have been in the range 400K - 600K (500K +/- 20%). The values drift with age (usually upwards) and it is not unusual to find old 500K pots reading 700K - 800K or even occasionally higher but 1.4M plus is definitely not normal and suggests something wrong, possibly a poor connection where the lugs connect to the track or a badly worn / damaged track. The other possibility is that they are 1M pots, do you know for sure that they were originally 500K pots?

  6. #6
    Les Paul Forum Member Hamerfan's Avatar
    Join Date
    Dec 2004
    Location
    From the best part of Germany - Bavaria
    Posts
    714

    Re: 50's pots and high resistances. How do they affect tone?

    Quote Originally Posted by PaulD View Post
    No, if they are 500K pots then the value when they were manufactured would have been in the range 400K - 600K (500K +/- 20%). The values drift with age (usually upwards) and it is not unusual to find old 500K pots reading 700K - 800K or even occasionally higher but 1.4M plus is definitely not normal and suggests something wrong, possibly a poor connection where the lugs connect to the track or a badly worn / damaged track. The other possibility is that they are 1M pots, do you know for sure that they were originally 500K pots?
    The IRC pots have a different code. Read here:
    https://www.guitarinsite.nl/serienum...tmeter_eng.php

  7. #7
    Les Paul Forum Member thin sissy's Avatar
    Join Date
    Jan 2006
    Location
    Sweden
    Posts
    2,431

    Re: 50's pots and high resistances. How do they affect tone?

    Quote Originally Posted by PaulD View Post
    No, if they are 500K pots then the value when they were manufactured would have been in the range 400K - 600K (500K +/- 20%). The values drift with age (usually upwards) and it is not unusual to find old 500K pots reading 700K - 800K or even occasionally higher but 1.4M plus is definitely not normal and suggests something wrong, possibly a poor connection where the lugs connect to the track or a badly worn / damaged track. The other possibility is that they are 1M pots, do you know for sure that they were originally 500K pots?
    They were all 500 kOhm speced pots (original with the guitar), they say so on the metal casing. Do you think the lowest reading ones are still useable? Since I know that the owner of the guitar swapped them out in the early 70's, I really don't know what to think about them being worn out .

    I will make a spreadsheet of the taper of them, perhaps that will tell me something of their functionality?
    This is a song from the new album, it's a deep meaningful song this one... No, it's not whiskey in the fucking jar... Philip Lynott

  8. #8
    Les Paul Forum Member thin sissy's Avatar
    Join Date
    Jan 2006
    Location
    Sweden
    Posts
    2,431

    Re: 50's pots and high resistances. How do they affect tone?

    Quote Originally Posted by Hamerfan View Post
    The IRC pots have a different code. Read here:
    https://www.guitarinsite.nl/serienum...tmeter_eng.php
    Thanks man! These are 500 kOhms speced pots from 1954.
    This is a song from the new album, it's a deep meaningful song this one... No, it's not whiskey in the fucking jar... Philip Lynott

  9. #9
    Les Paul Forum Member
    Join Date
    Jun 2007
    Location
    England
    Posts
    476

    Re: 50's pots and high resistances. How do they affect tone?

    Quote Originally Posted by thin sissy View Post
    They were all 500 kOhm speced pots (original with the guitar), they say so on the metal casing. Do you think the lowest reading ones are still useable? Since I know that the owner of the guitar swapped them out in the early 70's, I really don't know what to think about them being worn out .

    I will make a spreadsheet of the taper of them, perhaps that will tell me something of their functionality?
    The lower reading ones are within the range that might be expected for '50's pots and should certainly be fine to use. The higher reading ones may also still be useable (albeit they might sound somewhat bright if used as volume controls) but the fact that they are so far out of spec suggests that there may be something going on other than just normal age related drift. One thing you could check is the "low side" resistance between the outer lugs and wiper (centre lug) with the pot turned all the way up and down, you should get a fairly low reading (a few ohms up to maybe a maximum of a couple of hundred ohms), anything significantly higher might indicate a bad connection between the lug and the track.

  10. #10
    Les Paul Forum Member
    Join Date
    Apr 2006
    Posts
    217

    Re: 50's pots and high resistances. How do they affect tone?

    I'd randomly mix & install them without looking.. like they probably did at the factory, lol. Then anyone who plays it will wonder how it gets that unique blend of tones.

  11. #11

    Re: 50's pots and high resistances. How do they affect tone?

    Quote Originally Posted by denwing View Post
    I'd randomly mix & install them without looking.. like they probably did at the factory, lol. Then anyone who plays it will wonder how it gets that unique blend of tones.

  12. #12

    Re: 50's pots and high resistances. How do they affect tone?

    Volume pot value has a huge impact on the sound. Bigger value gives more tops and a more open sound. In my experience a big value volume pot in the neck position works beautifully if you have an over wound neck pickup. On a lower wound pickup a big value pot won't sound great. Bridge pickups sound too bright and harsh with a big value pot. Of course this depends on the actual pickup by in my experience 420k to 480k gives a thick slightly compressed bridge pickup and anything above 500k gets too bright, usually (my mate has a 560k pot in his junior and it absolutely kills). You can try any value tone pot and turn it down to where it sounds right. I hope that helps

  13. #13
    Les Paul Forum Member ChevChelios's Avatar
    Join Date
    Jan 2012
    Location
    Where the wind cries Mary
    Posts
    774

    Re: 50's pots and high resistances. How do they affect tone?

    Considering that you're having P90s in your guitar, these values are fairly high. I'd probably try the two lowest values for the neck volume and tone and get some newer 500 to 550k for the bridge pickup. I make my own (VIPots at vintageinspiredpickups.com), but there are quite a few modern pots out there that you might like, too.
    Not sure if I'd use those 1M pots in that guitar.

  14. #14
    Les Paul Forum Member thin sissy's Avatar
    Join Date
    Jan 2006
    Location
    Sweden
    Posts
    2,431

    Re: 50's pots and high resistances. How do they affect tone?

    Thanks guys! Looks like I've got some thinking to do . The bridge PU is pretty bright (I like that), might not be the best idea to put a high resistance pot there. But on the other hand, I don't know what the currently installed pots read eaither .

    ChevChelios, I actually own a set of four VIPots that I haven't installed in anything. One option would be to put the 670 kOhm IRC pot on the neck volume, and put VIPots on the other positions.

    But there's a part of my brain that says "don't fix something that aint broke". I just recieved conductive faderlube, I'll put that on the carbon track of the pot I opened and cleaned with electrical cleaner, and then I'll reassemble it again. The pot looked in very good shape, so I think I won't open up the remaining, just do a little cleaning and lubing through the hole in the pot casings.

    I'll try to put up some pics of the pot I opened up, perhaps that can tell you guys something.
    This is a song from the new album, it's a deep meaningful song this one... No, it's not whiskey in the fucking jar... Philip Lynott

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


Scroll Down And Click On All Of Our Sponsors' Logos For Their Websites!



i