Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Princeton Reverb Vibrato tweak!

Discussion in 'Amp Central Station' started by kosmonautmayhem, Mar 5, 2012.

  1. kosmonautmayhem

    kosmonautmayhem Tele-Meister

    432
    Jan 11, 2010
    Chicago
    I would go with the 220k. (1/2 watt is perfect)

    If its tooo much intensity and you can't manage it with the knob, then you can try to increase the bias like I did. Increasing the power tube bias too much and the trem will completely disappear. :eek:

    I went with a 220k 1/2 carbon comp I had and bumped the bias up from 18mA to about 21mA per 6V6. Nice results. At 18mA it was too deep and started to somewhat resemble a choppy BF-style roach trem.

    Still haven't found time to make a clip yet....its coming though. I promise! :)
     

  2. kosmonautmayhem

    kosmonautmayhem Tele-Meister

    432
    Jan 11, 2010
    Chicago
    side-note

    Just remembered this....

    I've seen a few earlier 6G2 Princeton's that came with 220k as the stock value for trem intensity. But as in the PR's the bias settings will have a lot of effect on intensity, so its a little bit of a balancing act to find what you like.
     

  3. sonicreducer

    sonicreducer TDPRI Member

    7
    Aug 22, 2010
    Los Angeles
    Ok, so the bias adjustment is to set the depth of the trem to taste. I thought maybe that changing the resistor would, by default, change the current bias and I'd have to compensate to bring it back to where it is. Thanks a lot Kosmo! I can't wait to try it out.
     

  4. kosmonautmayhem

    kosmonautmayhem Tele-Meister

    432
    Jan 11, 2010
    Chicago
    oh...I'll clarify the balancing act spiel....

    First - I'll give the usual disclaimer: TUBE AMPS CONTAIN LETHAL VOLTAGES. Be extremely cautious when working on amps. If you don't have any experience in this area you may want to consult a tech.

    However, I'm happy to advise so long as you're comfortable with this work. Its a pretty easy mod actually. You may not even need to bother adjusting the bias if you like the results of swapping the 1M resistor with a 220k.

    To answer your question: The trem intensity resistor does not change the power tube bias. It just affects how much signal is coming through to feed the oscillation of the trem. PR's trem is bias-vary, which gets its pulse from the power tubes. For a good intensity range people recommend keeping the power tubes biased cool (16-18mA is usually pretty good).

    Power tubes are biased via another resistor on the little board next to the pilot light. Its in parallel with an electrolytic cap on the board.
    *Forgot to mention I have a bias pot installed in mine as opposed to the fixed resistor. Helps when making quick adjustments. :cool:

    Let me know if you have other questions. Happy to help you out.

    kM
     

  5. ArcticWhite

    ArcticWhite Tele-Meister

    171
    Apr 14, 2009
    Portland Oregon
    Hi guys.
    I know this is an old thread.
    I swapped my two .01 capacitors for .02's, and the tremolo slowed down, but not enough. So I put the .01's back on in parallel with the .02's. But the tremolo is still too fast.
    I timed it on the slowest setting and it's about 200 beats per minute. The OP was getting 140 with .02 caps, and mine are effectively .03's!
    I'm wondering if I can't slow it down further using a resistor - since the rate is set using a potentiometer in the first place.
    Is that correct? If so, why bother with swapping the caps in the first place?
     
    Last edited: Feb 16, 2017

  6. ArcticWhite

    ArcticWhite Tele-Meister

    171
    Apr 14, 2009
    Portland Oregon
    Alright then.
    Answered my own question. The tremolo speed pot is set to zero resistance at it's slowest speed. I tried other resistors in parallel with the 100K R at the potentiometer ground to no effect.
    Then I raised the cap value to .25. This is diZy tremolo.
     

  7. StarsOfTheLid

    StarsOfTheLid NEW MEMBER!

    Age:
    32
    2
    Nov 10, 2017
    germany
    Hi guys, I am looking for help. I wanna slow down the trem of my BF Princeton Reissue but I don't get which one of the caps is the one that needs to be replaced. Can you please tell me?

    Also interested in increasing the intensity but I don't know which of those resistors is the one. Any help appreciated!
     

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  8. StarsOfTheLid

    StarsOfTheLid NEW MEMBER!

    Age:
    32
    2
    Nov 10, 2017
    germany
    Speed issue solved! Now I only got the intensity increase left to solve. Can anyone guide me into that?
     

  9. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    Intensity is partly dependent on power tube bias in a PR. Too hot or too cold, and it gets weak. I'd try a very slight tweak there, after marking the bias pot (R22) or taking a picture to record the original position. Make a very small tweak, and listen.
     

  10. Mutato

    Mutato Tele-Meister

    350
    Sep 16, 2008
    Rhode Island
    I had my tech mod my tremolo depth on my '77 PR to get more intensity out of it. Found somewhere (possibly here?) about certain resistor change. Sounds amazing now.
     

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