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Fender DRRi broke

Discussion in 'Amp Tech Center' started by xjazzy, Jul 10, 2018.

  1. schmee

    schmee Friend of Leo's

    Jun 2, 2003
    northwest
    I'm a bit skeptical if the caps are the actual issue also. Often leaky caps still work.. for some time. But hopefully that will fix it.
     
  2. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    If presented with that amp, I would not wonder what else was needed until the electrolytics were replaced. Ommv....but those caps should not be subjected to current, ime.
     
  3. corliss1

    corliss1 Friend of Leo's Platinum Supporter

    Sep 13, 2008
    Lansing, MI
    This. Why bother speculating on anything else until we know the power supply is working? If the power supply isn't happy nothing else will be either.
     
    SngleCoil, Wally and D'tar like this.
  4. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    Very much agreed. Actual leaking caps like those will cause weird issues, and carry a risk of failing catastrophically and explosively.

    There's often more than one issue in any troublesome amp, so if the sound quality doesn't return you may want to study up on taking measurements or track down a good tech to finish the debugging. As a nice plus, the Fender service documents list the expected voltages to be found and the test conditions required to check them which is a big help to anyone working on one of these.
     
    robrob and Wally like this.
  5. wanderin kind

    wanderin kind Tele-Meister

    Age:
    63
    269
    Apr 24, 2018
    Olympia WA
    check your effects loop jacks or preamp/pwr amp jacks if the amp has them. try a patch cord from send to return. this can be done without any work like taking the chassis apart. if the cord fixes it, use some spray in there. alcohol will work if stranded on a desert island.
     
  6. corliss1

    corliss1 Friend of Leo's Platinum Supporter

    Sep 13, 2008
    Lansing, MI
    No such thing on these amps.
     
  7. xjazzy

    xjazzy Friend of Leo's

    Feb 17, 2007
    Portugal
    New caps in place and amp sounding good!!
    Thanks guys for your help.
     
    viccortes285, Flaneur, robrob and 3 others like this.
  8. xjazzy

    xjazzy Friend of Leo's

    Feb 17, 2007
    Portugal
    Well, I finally had time to give the amp a spin along with my other amps and, maybe my ears are playing tricks on me but, I think it was louder before!
    I put a set of new power tubes, BIAS'd them and I think it helped slightly but still not completely convinced it sounds as loud as before the caps went kaput...
     
  9. corliss1

    corliss1 Friend of Leo's Platinum Supporter

    Sep 13, 2008
    Lansing, MI
    Do you still have the original power tubes? You could try putting those back in, adjusting the bias, and then seeing if you hear anything different.
     
  10. xjazzy

    xjazzy Friend of Leo's

    Feb 17, 2007
    Portugal
    I was using the "original" power tubes. The ones that were there when the caps started to give me problems.
    Since I thought the volume was not ok, I tried a new set and I'm not sure it helped but I'm pretty sure it did not returned the amp to the same volumes pre-bad caps.
     
  11. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    IMHO and ime, this is why one would like to have a voltage chart and bias numbers done when an amp is functioning properly. If one has such a baseline, one has something with which one can compare after any changes occur.
    I also have noted many situations where oowners of guitars and amps become very ‘aware’ after something occurs and this ‘awareness ‘ can lead to impressions that are other than reality based. Even if these impressions are based on some actual difference, it takes the numbers to come to understand what is going on. So, imho, a voltage chart needs to be made. That includes bias numbers including plate dissipation. As a final number, one would want to know the actual output to the speaker in watts. You may still need a tech if this is too far into the situation.
     
    robrob likes this.
  12. xjazzy

    xjazzy Friend of Leo's

    Feb 17, 2007
    Portugal
    I'd definitely need a tech to do that...
     
    Wally likes this.
  13. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    I understand. I was simply laying out what has to be known in order to understand any perceieved changes in how the amp is working. Perceptions....what a concept, eh?
    I say play it.
     
    xjazzy likes this.
  14. viccortes285

    viccortes285 Tele-Holic

    Age:
    69
    980
    Jan 14, 2017
    Phoenix
    Current draw depends a lot on what brand 6V6 you are biasing. As others have said, "use your ears" but you need to use care. I only install NOS 6V6 tubes in any amp I service such as RCA, GE, Sylvania, Philips, Tung-Sol and others. The 6V6 is my favorite tube and I've been collecting them and setting bias like this for 20+ years. I set bias between 25-30 ma while the owner is playing. When he or she says that's good then the bias is set. The plate voltage on DRs will be between 410 & 435. I've never had a problem or complaint using this method.
     
  15. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Using those numbers and figuring for the two extremes of what plate dissipation factors that could be observed, one gets ...
    25ma at 410Pv.....73%
    30Ma at 425Pv....91%

    25ma, 425Pv....76%
    30ma, 410Pv...88%

    Ime, healthy 6V6’s will handle all of those scenarios without redplating. The higher plate dissipation figures will lead to more rapid Tube wear. The trade off in sonics versus tube wear is generally not something that I would advise for at least the highest two plate dissipations there. Ommv.
     
    viccortes285 likes this.
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