Is My PRRI Faulty/Normal?

Discussion in 'Amp Central Station' started by markesquire, Jul 5, 2020.

  1. markesquire

    markesquire Tele-Afflicted

    Sep 20, 2008
    I really like the tone from my PRRI, but I’m having problems with both the reverb and tremolo.

    The tremolo just isn’t as deep as I’d like — my Boss TR-2 goes slower/swampier and sounds deeper.

    The reverb has two problems. First, it creates a pretty noticeable hum/hiss when the reverb is turned up. Second, the reverb just seems weak, both in terms of mix level and short decay time. I recently played a DRRI and the strength/length of its reverb was night and day better than my PRRI. I’ve asked 2 techs about this, and they say my amp is within Fender specs and that noise just comes from turning the reverb up.

    Do other PRRI owners have the same issues? Should there be that much of a difference between the reverbs in the PRRI and DRRI or TRRI?
  2. Uncle Daddy

    Uncle Daddy Tele-Afflicted

    Sep 26, 2015
    Maldon, England
    It's normal to get a bit of hum from the reverb when it's near the end of the dial. You ca always try different tank for a better delay.

    The trem is a bit weak. There's a mod involving a resistor that slows it down.
  3. Peegoo

    Peegoo Friend of Leo's

    Oct 11, 2019
    Planet Peegoo
    How old are the tubes? Swap in some known good ones and see if it changes anything.
    Wally and Lowerleftcoast like this.
  4. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    FYI....V2 is a 12AT7 and is the reverb driver tube. One triode in V4 is the tremolo tube. The trem effect can be modded to be slower. Also, the trem effect is a bias vary circuit and therefore it’s strength is directly related to the power tube biasing. should compare favorably to any of the other BF Reverb based Fenders. Something is not correct there, ime. In addition to that driver in V2, one triode in V3 is the reverb return tube. And....I have measured reverb tanks that looked good on an ohmmeter but that yielded very weak and dull reverb. A replacement tank fixed those reverbs. An inquiring and experienced tech is a valuable asset.
    corliss1 and Paul G. like this.
  5. schmee

    schmee Doctor of Teleocity Silver Supporter

    Jun 2, 2003
    For Reverb I would try a different tube in V2 first. The RI's seem to have common issues with Reverb. And yes, if your reverb is turned up in the 5-10 range it will be noisy. Maybe you need a quality tank. You could try a 4 spring tank if it's a 2 spring.

    There's a common mod for stronger tremelo if you want. Not sure on your RI PCB where it is, but if you can find the resistor shown below on yours: (as you can see it's a 1 meg that is tied to the string of 3 caps)

    Princeton Rev Tremelo mod
    There are normally 3 caps tied to your tremolo circuit. two .01s and one .022. Pull a .01 an
    d replace with a .022uF. That will slow it down. You will also find a 1M resistor in that circuit, I replaced mine with a 220K. That will highly increase the intensity. you can use a 470K too but I liked the 220K so I used that.
  6. rangercaster

    rangercaster Poster Extraordinaire

    May 8, 2008
    Knoxville TN for now
    Just use the Boss ...

    Problem solved !!!
  7. 100LL

    100LL TDPRI Member Ad Free Member

    Jun 23, 2020
    Houston, TX
  8. EsquireBoy

    EsquireBoy Tele-Afflicted

    Jun 21, 2019
    Paris, France
    For the reverb you could try to rotate the tank or turn it upside down to see if it improves things hum-wise.
    I do not remember the reverb to be weak on the PRRI I had though.

    For the tremolo, you can try lowering the bias of the amp. It will make it deeper. There is a bias pot accessible through a hole in the chassis near the transformer.
    Put a mark on a piece of tape to remember the original setting, and use an insulated plastic screwdriver to be perfectly safe.
    schmee likes this.
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