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Tone controls

Discussion in 'Amp Tech Center' started by ce24, Dec 5, 2018.

  1. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    So it seems the tone controls on my 69 NV Princeton have no effect .. this is a new development .... It has had a complete service by Wally just recently...... Tone is great, plays well. I play it at about 5 on the vol. Any ideas tdpri?
    Cheers
    Ce24
     
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  2. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia
    Put an ohm meter across them and turn them. That would be the first step
     
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  3. uriah1

    uriah1 Doctor of Teleocity Ad Free Member

    Feb 12, 2011
    Around
    Odd. You may ask Wally. did you have tone stack mods. Pop the hood open, perhaps a dropped piece of solder or dangling lead from shipping travel, or other.
    wish you luck.
     
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  4. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    If the 6.8k mid resistor's ground connection is broken the tone stack is lifted. This is how a raw switch works. Measure the resistance from the bass pot's output (connected to the mid resistor) to ground. It should measure 6.8k. It's probably an open connection.
     
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  5. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    Thanks guys... I'm home with with a sore throat and can check it all today.... Will report back..
     
    Last edited: Dec 6, 2018
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  6. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Iirc, I replaced that 6.8k midrange resistor with a larger value to pump up the mids. Hopefully that connection did not go bad. Ce24, if the amp has gotten really hot and lively, what Rob describes may be exactly the problem.
     
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  7. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    Ok here we go....no broken or bad solder joints.
    MM OHM setting 2k.

    Wally replaced the 6.8 resistor with a 220 ohm to boost the mids.
    Oddities
    Measuring the 220 bass pot to ground gives me no reading.... However when I measure across the lugs i get a 0 reading on 10 and a .015 at 0 on the treble pot and 0 to .029 on the bass pot going from 0-10

    When i probe across the 220bass pot resistor I get no reading....
     
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  8. aerhed

    aerhed Tele-Afflicted

    Age:
    59
    Dec 24, 2016
    Boulder, WY
    220?
     
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  9. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    Yep...red red yellow gold. Suppose to boost the mids.
     
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  10. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    Can a too hot bias cause this?
     
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  11. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    I'm getting some movement. I checked bias with my Eurotubes bias plug... The simple one and it showed 20ma so I boosted it to 24.4-5 and I'm getting some variance
     
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  12. Lynxtrap

    Lynxtrap Tele-Meister

    477
    Feb 29, 2016
    EU
    220 ohms to ground? Seems like close to nothing to me...
     
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  13. jhundt

    jhundt Doctor of Teleocity

    Age:
    64
    Mar 23, 2003
    Netherlands
    if that is in fact a 220-ohm resistor, that would explain the lack of action on the tone controls. Perhaps it was inadvertently placed instead of a 22k (which is what a red-red-yellow should be) why don't you check the value again with your meter?
     
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  14. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    You're on the wrong range. Trying to measure a 22k resistor, let alone a tone pot (typically 250k to 1m are used) will read off scale high assuming the meter will recognize it at all. Start on the highest range of your meter and work down until you get useful readings.
     
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  15. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    Thanks Clintj.... Will do.....
     
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  16. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Ce24, the work order shows that I put a 22k ohm reisitor in place of the 6.8k ohm midrange resistor. If that resistor is not red, red, orange then I made a mistake. However, the amp didn’t sound as if I did make a mistake in the selection of the resistor when I shipped it off....and the tone stack has worked these many months....what 8 or 9 months? What is the date on the work order. Check my solder joints of that resistor. Measure it with one end lifted.
    If in fact I did make a mistake in the selection of the resistor...the repair is on me. Ship it back..I’ll fix it, and throw in a primo NOS tube as compensation for your shipping costs, and ship it back to you at my expense.
     
    Last edited: Dec 8, 2018
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  17. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    IMG_20181208_122432595.jpg here is a pic on the right, the resistor that was put in. I changed it out and put the original 6.8 back in and all I good in the universe.... Thank you so much fellow forumites....much appreciated!
    Cheers
    Ce24
     
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  18. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    Thanks for such a generous offer. I have skills to revert it back to the originsal 6.8. plus I've learned a thing or two. Well worth process.
    I have done the work and now the amp is fine.
    Thanks Wally!!
     
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  19. Bluey

    Bluey Tele-Meister

    Age:
    57
    109
    May 15, 2018
    Australia
    Wow..wish you could get such service & honesty in the rest of the world!!!
     
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  20. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Well, it seems I did make an error....proving once again I am a mere human, right? I picked up a 220K resistor....duh! Serious midrange was probably causing the movement of the bass and treble controls to be obscured.
    Note to self: double check everything.
     
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