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Rewiring An Oldie

Discussion in 'Pickups & Electronics [BG]' started by Barryll, Aug 26, 2007.


  1. Barryll

    Barryll

    Sep 29, 2006
    Kneevada
    The wiring in my otherwise pristine 40+ year old Klira brand, Hofner knock off(Beatle bass) is in sad shape and at least one component may be going bad – scratchy pot & intermittent PU switch.

    I’m considering replacing the vol & tone pots and changing the pickup selector switch to a “blend” pot, but I’m not sure what value pots to use and the original pots are not labeled.

    The original pickups are passive, and I’m hoping they don’t need to be changed.

    I’m aware of the concept that 250K pots give a slightly warmer tone than 500K because the 250K bleeds off some of the high frequencies, but I’m not sure that bleeding off some highs is a good idea because I use a SansAmp Para Driver pre-amp to shape the tone. My thinking is that if those highs are bled off before they get to the pre-amp, I can’t shape them.

    Most of the time I try to get this old bass to sound similar to an upright bass, and the Para Driver does a decent job. I’m hoping that choosing the correct values for the vol, tone, and blend pots will help get me even closer to the sound of an upright bass.

    Can you please help me choose the pot values?

    Thanks
     
  2. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    FWIW:

    If you're getting sound out of the pups then they don't need to be changed and I would disturb them as little as possible.

    To me 250/500 pots is splitting hairs tonewise. You can put a meter on the pots (once disconnected). Just use the same value blend as volume.
     
  3. Before replacing the switch and pots try some contact cleaner.
     
  4. Barryll

    Barryll

    Sep 29, 2006
    Kneevada
    Thanks for the replys. I do appreciate them.

    I was hoping for a few more opinions to ponder, so here is the core of my question again.

    I’m considering replacing the vol & tone pots and changing the pickup selector switch to a “blend” pot, but I’m not sure what value pots to use and the original pots are not labeled.

    I’m aware of the concept that 250K pots give a slightly warmer tone than 500K because the 250K bleeds off some of the high frequencies... but I’m not sure that bleeding off some highs is a good idea... My thinking is that if those highs are bled off before they get to the pre-amp, I can’t shape them.

    Can you please help me choose the pot values?

    Thanks Again
     
  5. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Meant to post this other day. Most hollowbody's are a nightmare to work on cause there's no access to the components. The pot cleaner is a good idea but I was assuming you'd have to remove the pots to even use it. If it has an F hole(s) you might be able to loosen the pots nut and rotate the lugs around and take a shot at them through the F hole. But I sure wouldn't remove them, clean them, and stick them back in unless that's a simple process. I'd get new ones.

    If you don't have easy access, there was a good post within the last month or so where a TBr mention tieing strings to the pots and using them to pull the pots up through holes. I'd hunt that post down if that's your situation cause those things are grief.
     
  6. DavidRavenMoon

    DavidRavenMoon Banned

    Oct 20, 2004
    I had one of those basses back in the 70's! It was a weird natural with orange creamcicle burst. I seem to remember I liked the tone of the pickups. I had Rotosound black nylon tapewounds on it.

    Working on a hollowbody can be trying at best. You need to wire up the harness and pull everything through the F holes or pickup openings.

    For scratchy pots... if all else fails, try WD-40. I had it save some otherwise uncleanable pots.
     
  7. Barryll

    Barryll

    Sep 29, 2006
    Kneevada
    Wow, suddenly a bunch of help....Thank you.

    This bass is very easy to work on; the controls are all mounted on a chrome plated metal plate that is held in place with a few screws. All I do is loosen the screws, and I have access to both sides - that part is easy.

    What I need help with is the value of the pots.

    I’m aware of the concept that 250K pots give a slightly warmer tone than 500K because the 250K bleeds off some of the high frequencies... but I’m not sure that bleeding off some highs is a good idea... My thinking is that if those highs are bled off before they get to the pre-amp, I can’t shape them.

    Should I use 250K pots or 500K or something else?

    Thanks Again
     
  8. I just ordered a 500k blend, a 250k volume, a 250k for tone pot and a .47 Orange drop cap to go into my Fender Jazz. I was told that the blend will act as a 250k depending on what position its in. I dont know if this is true. I will need to check it with a meter when i get it. Since this is kind of related to Barryll's question, I am hoping someone with more knowledge can chime in.
     
  9. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    If that's so then I would just get some pot cleaner/lubricant from radio shack and spray the pots first.

    Seems you've had 4 or more responses to the pot values - what is about them that you don't understand?
     
  10. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    FWIW:

    a pot is a variable resistor - so the resistance varies depending on where the wiper is. Where the technical aspects of that fit in with a blend I don't know. In practice I haven't found any difference of signficance between 250 and 500's - that's the part I want to know about.
     
  11. DavidRavenMoon

    DavidRavenMoon Banned

    Oct 20, 2004
    I've had back luck with that stuff. I have Behringer mixer that had pepsi spilled in it. Nothing would clean the faders. The Radio Shack stuff made it worse. I almost threw it out, and then in desperation I tried WD-40. That fixed it like a charm!

    I agree. The low output pickups in that bass don't need anything more than 250K.
     
  12. Barryll

    Barryll

    Sep 29, 2006
    Kneevada
    More good replies, Thank You.

    I know what a pot is and how it works, but I'm confused about what happens acoustically when a signal passes through a pre-amp and then to the main amp speakers and to our ears.

    If two identical basses are set up, one with 250K pots and the other with 500K pots, their signals run through identical pre-amps and then to identical main amps, speakers, etc, could the the 'control knobs' be adjusted such that our ears would think they sound alike - in my case like an upright bass? Someone else will want a Heavy Metal sound etc...

    If our ears think the two basses sound alike, then it would seem like it shouldn't matter much, what value pots are used. But unless I'm mis-reading the responses so far, not everyone agrees with that concept.

    Sooo, what value pots should be used to make this oldie sound most like an upright bass?

    Can the pre-amp compensate for either some highs or some lows not really being there, or at least make our ears 'think' it's all there?

    Thanks Again....
     
  13. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    I mention the RS stuff cause it's comparatively cheap (cheaper than like Stewmac's shipping alone) and accessible to most players. I've had it work for me more times than not but it's not like it's anything I use a lot. Probably not the best but it's not like I'm hosing a WW down with it. Good enough for me.

    I have used WD-40 a time or two and seemed like it was fine but read some stuff about it not being a lubricant so picked up the RS stuff next time I got around one. I don't recall seeing anybody else recommend WD. No big deal either way. After reading your post I would try it if I didn't get results with the RS - then I'd follow up with the RS for the lubricant. Whatever works.
     
  14. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Sorry, it was directed to David and I knew he knew (or assumed anyway).

    Walter Woods.

    Only thing I know that works on a Wild Woman is to put as much distance between you and her as possible - in the US preferably the opposite coast.

    Short of a 44 that is.
     
  15. DavidRavenMoon

    DavidRavenMoon Banned

    Oct 20, 2004
    WD-40 is what's called a penetrating oil. So it is a lubricant. It's not made for things like this, but I've had it work when the regular contact cleaners didn't. It is advertised as getting moisture out of electrical contacts... which is why I tried it. Usually the Radio Shack stuff works fine. The contact cleaners used to be better, but they had to change the formulation to limit CFC's.

    I only tried the WD-40 because nothing else was working. Since then I've had it fix several scratchy pots that the normal cleaner wouldn't fix.

    I've never even seen a Walter Woods amp in real life. I'd love to try one out!
     
  16. Barryll

    Barryll

    Sep 29, 2006
    Kneevada
    All this talk about wild women & WD-40 is interesting, but what about.....

    If two identical basses are set up, one with 250K pots and the other with 500K pots, their signals run through identical pre-amps and then to identical main amps, speakers, etc, could the the 'control knobs' be adjusted such that our ears would think they sound alike - in my case like an upright bass? Someone else will want a Heavy Metal sound etc...

    If our ears think the two basses sound alike, then it would seem like it shouldn't matter much, what value pots are used. But unless I'm mis-reading the responses so far, not everyone agrees with that concept.

    Sooo, what value pots should be used to make this oldie sound most like an upright bass?

    Can the pre-amp compensate for either some highs or some lows not really being there, or at least make our ears 'think' it's all there?
     
  17. DavidRavenMoon

    DavidRavenMoon Banned

    Oct 20, 2004
    Yeah like with my old Ford Contour, which didn't want to run when it rained. :rollno:
     

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