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P-90 circuit technical questions

Discussion in 'Just Pickups' started by Obsessed, Jan 1, 2021.

  1. Obsessed

    Obsessed Telefied Silver Supporter

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    So, I have determined that the volume pot is faulty on my very inexpensive Grote "Jazz" this morning, so I might as well upgrade to CTS pots. I am a noobie with P-90s, so I am seeking out recommendations for tone capacitor value and whether I should go to audio taper pots like I put in my Sheraton II? I love the sound as is and it has a green cap with "2A473J (or perhaps "I") if that helps. Since I have already had to replace the output jack with a Switchcraft, I might as well ask about P-90 replacements too. I play blues/blues rock through this hollowbody. Thanks for any and all help. IMG_4850.JPG
     
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  2. BorderRadio

    BorderRadio Doctor of Teleocity Silver Supporter

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    500k volume, 250k tone, 50s wiring, audio taper. That has always been a winning combo for the low wind P90s I've played.

    Whats the resistance on the stock P90?
     
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  3. Wyzsard

    Wyzsard Friend of Leo's

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    Why change what you love ?Replace the pots and rock on.
     
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  4. Obsessed

    Obsessed Telefied Silver Supporter

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    Ahh, interesting. Both pots are 500K and the P-90 measures at 6.4. I did the 50s wiring on my Sheraton years ago with great success. I suppose I can just look up the 50s wiring diagram for just the two knob arrangement. Thank you so much for the ideas.
     
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  5. Obsessed

    Obsessed Telefied Silver Supporter

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    Well, that was my original thought too, but now that I am in the thick of things and all of these P-90 experienced people here, I thought I would take advantage of the knowledge base. Nevertheless, I really want to get it back quickly and was hoping it was just a crappy solder job, which BTW they look pretty crappy.
    Thanks though for keeping me anchored to the original intent.
     
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  6. Tuxedo Poly

    Tuxedo Poly Friend of Leo's

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    The 2A 473J cap is 0.047uF 5% tolerance.
     
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  7. Dacious

    Dacious Poster Extraordinaire

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    https://www.pinterest.com.au/pin/576038608565548880/
    Use the Les Paul Jnr 50s wiring. Tons of examples on the web.

    IMG_20201124_174015.jpg
     
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  8. Obsessed

    Obsessed Telefied Silver Supporter

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    Thanks. I was hoping someone could confirm that. Since it appears that most of the electrical components are sketchy at best, I thought I would replace the cap too.
     
  9. Obsessed

    Obsessed Telefied Silver Supporter

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  10. Obsessed

    Obsessed Telefied Silver Supporter

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    Anymore input before I commit?
     
  11. hamerfan

    hamerfan Tele-Meister

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    Two 500k pots are okay, if they turn smoothly. The cap is as bit high, I prefer .015 or . 010 with neck pickups. For the 50ies wiring you only have to swap one wire.
     
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  12. Addnine

    Addnine Tele-Holic

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    With P90's I like 500k/.022 for blues, a more penetrating sound, 500k/.047 for clean and jazz.
     
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  13. AJBaker

    AJBaker Friend of Leo's

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    I would recommend 500k audio pots and a .022uF cap.

    A 250k tone pot would also be ok, though I might go for no-load for added options.

    50s wiring has advantages and disadvantages, on my Les Paul I found I liked it on the neck pickup, but preferred modern wiring on the bridge pickup.
     
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  14. wevard

    wevard TDPRI Member

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    If you’re planning on ordering two 500k pots and you have a digital multimeter, measure the resistance of the faulty volume pot and the new ones. Choose the replacement with the value closest to the original if you want the guitar to sound as close as possible to what you’re used to. Even 50kOhm can make a difference.
     
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  15. TimTam

    TimTam Tele-Holic

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    I have a Grote. FWIW its components are mostly fine. A cap is not a mechanical part. It either works or it doesn't. It either matches the capacitance value on the label (or is within the specified tolerance) or it doesn't. Plus the first half of the tone rolloff is all due to the tone pot; the cap only kicks in for the bottom half.

    Anyone who solders guitars for a living is highly unlikely to produce bad solder joints. It's a simple skill. By 100 guitars or so (less for many people), you're as good as anyone at it. ;)

    You say you "love the sound". Be glad that great sounding guitars/pickups are not necessarily expensive. So I'm not clear on why you want to mess with other components. If it were mine, I'd measure the pot that needs replacing and match it with one of similar measured resistance, as suggested above. And leave it at that.
     
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  16. Wallaby

    Wallaby Friend of Leo's

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    I am probably the oddball in this thread, but I like 500k/500k "vintage" taper pots and a .015uf cap for a neck P90, modern wiring.
     
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  17. jvin248

    jvin248 Doctor of Teleocity

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    +1 measure kohms of the volume pot you have and match a replacement when reinstalling, if you like the tone now.

    I avoid all 50s wiring schemes because the volume and tone knobs interact ... like turning the tone knob drops the volume. Most of the fans of 50s wiring never touch their tone knob but I use it and found that odd interaction. So be cautious before implementing.

    .
     
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  18. beanluc

    beanluc Tele-Holic

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    0K and ∞K replacements are pretty easy to come by, depending how it measures out :cool:
     
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  19. Addnine

    Addnine Tele-Holic

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    P90's are a very versatile pickup and can work differently but well with a wider range of cap/pot values than other kinds of p/u. I also find that the cheap ones sound very nearly as good as the premium ones. Alnico/ceramic: they don't really seem to care.
     
    Last edited: Jan 2, 2021
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  20. AJBaker

    AJBaker Friend of Leo's

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    You're right, and it comes down to whether you like that interaction. A cool effect is that you can 'hollow out' the sound by turning down volume and tone about halfway. The signal becomes much quieter and loses a lot of mids, but still sounds clear with some treble.

    I found this useful on a neck humbucker for cleaning up the signal without losing all clarity.

    On the bridge pickup, however, I found I couldn't properly dial out brightness, until I was way down on the tone knob (at which point it turns to mud).
     
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