1968 Fender Fibro Champ died

Discussion in 'Ampage Area' started by GreTschocaster, Mar 1, 2021.

  1. GreTschocaster

    GreTschocaster Synchromatic

    Age:
    67
    500
    Feb 11, 2013
    Canada
    Vibro not Fibro silly spell check!
    Need some help. This amp was given to me by my wife's stepfather 2 weeks ago. It worked perfectly until I went to use it this morning. Power light came on but there was no sound. Changed the patch cord and checked speaker connections, both were OK but still no sound. I noticed the 6V6GT and the 5Y3GT were not glowing. I swapped tubes from my '65 Champ (same tube values) still nothing. Took the covers off the 2 - 12 AX7's and both are glowing. This amp is totally original even has the ungrounded plug. I was thinking power transformer failure until I saw the 2 12AX7 were glowing. Any of you amp guys have ideas?
     
    Last edited: Mar 1, 2021
  2. tartanphantom

    tartanphantom Friend of Fred

    Age:
    57
    Jul 30, 2008
    Murfreesboro, TN
    I've honestly never owned an amp that had fibromyalgia... much less being the "Champ" of fibro...:D
     
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  3. slickfaster

    slickfaster Synchromatic

    998
    Dec 29, 2009
    USA
    If it were mine I wouldn’t fire it up n get it to a tech...
     
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  4. Mr. Lumbergh

    Mr. Lumbergh Country Gent

    May 14, 2013
    Initech, Inc.
    Autocowrecks will get you.
    Regarding the amp, it's gonna take a bit of investigation of the internal components but the capacitors in the power stage store enough charge knock you down or worse if you get a shock from them, so unless you know what you're doing and know basic safety measures such as how to safely discharge them, I'd take it to a tech.
     
  5. GreTschocaster

    GreTschocaster Synchromatic

    Age:
    67
    500
    Feb 11, 2013
    Canada
    I pulled the chassis but couldn't see any obvious issues like leaking caps or burnt resistors
     
  6. Mr. Lumbergh

    Mr. Lumbergh Country Gent

    May 14, 2013
    Initech, Inc.
    Do they look like the original caps? If so, they've likely failed even if you can't see any evidence of it. I already had to recap my Hot Rod built in '01 because the caps in the power stage were starting to fail.
    I still wonder why Fender insists on using those crappy capacitors from IC...
     
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  7. lathoto

    lathoto Synchromatic

    599
    Apr 23, 2020
    Ohio
    Probably an easy fix at this point. Take it to your amp guy. "It was working yesterday."
     
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  8. Andy Fortune

    Andy Fortune Gretschie

    354
    May 24, 2016
    Corning, NY
    Glowing preamp tubes just means the 6v winding on the power transformer is ok but not making it to the rectifier(5 volt winding) and power tube if they are not glowing )though it's harder to tell with them). Should be a simple thing to track down for a tech. Definitely do not power it up in the meantime. My bet would be a failed filter cap and power resistor in the first stage of the B+ voltage.
     
    Last edited: Mar 2, 2021
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  9. slickfaster

    slickfaster Synchromatic

    998
    Dec 29, 2009
    USA
    Do not let the smoke out of that vintage amp!!!
     
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  10. wabash slim

    wabash slim Gretschified

    Age:
    71
    Feb 10, 2010
    lafayette in
    It's over 50 years old. Components fail. Take it to a reliable tech.
     
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  11. swivel

    swivel Country Gent

    May 13, 2018
    PNW
    Yeah, tech time. Could be the filter caps, but could be a loose heater wire to the power tube. But if the rectifier is not glowing... hmmm. Could be the PT.
    It's a $350-400 amp so ask how much!
     
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  12. GreTschocaster

    GreTschocaster Synchromatic

    Age:
    67
    500
    Feb 11, 2013
    Canada
    I am old, retired, stubborn and have lots of time on my hand as well as reasonable soldering skills. So I would like to give it a try to fix it. If the PT is the culprit I would like to start there then replace the capacitors. Any easy way to test the PT? if all else fails I will take it to a tech.
     
  13. swivel

    swivel Country Gent

    May 13, 2018
    PNW
    Yeah, pretty simple amp. Do the filters first as they need done any way.
    Remove chassis.
    Plug it in
    KEEP YOUR FINGERS OUT OF THE CHASSIS!
    Measure the voltages
    [​IMG]
     
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  14. Randy99CL

    Randy99CL Country Gent

    Feb 17, 2020
    Albuquerque
    I was an aviation electronics tech in the Navy for six years, back in the '70s when there was still a lot of tube gear.

    Make some kind of grounding stick but it need not be elaborate. A 12" wood handle (dowel or broomstick) with 6" of some kind of stiff rod out the end (like a coat hanger wire). Solder a 3' flexible wire to that metal rod with an alligator clip on the other end.
    With a two prong (ungrounded) power cord I attach a wire from the chassis to the ground screw on an outlet.
    With power off and unplugged, attach the alligator clip to the chassis and touch both ends of every capacitor, every wire connection from a transformer and basically to be safe just touch every connection you see.

    With old circuits like this you can often spot problems with your eyes. Caps leak fluid and turn brown or pop open or do other things that tell they have blown. Resistors may overheat, turn dark and open or go to high resistance. Transformers often leak and smoke. Sniff around too, sometimes you can smell a bad component.

    You've probably checked them already but wiggle the tubes around in their sockets, take them out and reinsert them to make sure they have clean contacts. Tube sockets get hot and sometimes they corrode or whatever and don't make good contact with the pins.

    If you don't know basic electronics it's hard to troubleshoot but you can use a meter to check resistors, capacitors, and transformers. Use the schematic above and remember that sometimes other things in a circuit can affect a resistance reading so it isn't what is marked on the drawing.
    With all the tubes out the resistance measurements should be simple enough.

    Edit: plugging it in and checking voltages is something that a total novice should avoid until you've checked everything you can (as above). Obviously, working on a powered open chassis is extremely dangerous and the last thing an inexperienced tech should try. Better to check all you can yourself then take it to a tech for power on testing.
     
    Last edited: Mar 2, 2021
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  15. Henry

    Henry I Bleed Orange

    Apr 9, 2014
    Petaluma
    Good luck! We wouldn't want your retirement to end prematurely.
     
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  16. slickfaster

    slickfaster Synchromatic

    998
    Dec 29, 2009
    USA
    This cracks me up every time I read it.. 5626A8EE-E7E3-49D9-AECC-C422B1AC1549.jpeg
     
  17. GreTschocaster

    GreTschocaster Synchromatic

    Age:
    67
    500
    Feb 11, 2013
    Canada
    I am thinking this is beyond my ability. Best to take it to my tech.
     
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  18. drrohle

    drrohle Synchromatic

    829
    Jan 3, 2014
    Hays, KS
    The 5Y3 rectifier tube has it's own 5 volt filament winding in the power transformer. Either the winding has opened up or the 5Y3 is blown. Did I hear you say that you tried another 5Y3? Not sure why the 6V6 isn't lit up if the 12AX7's are. Unless it's filament is blown too. I'm sure the power light is on right? That runs off the 6V winding as well.
     
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  19. Jeff67

    Jeff67 Country Gent

    Age:
    54
    Nov 3, 2019
    Crockett, Texas
    Definitely take it to a tech- can't enjoy that retirement if you're not here, and we've lost enough people over the last year. Good luck, and let us know how it turns out.
     
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  20. GreTschocaster

    GreTschocaster Synchromatic

    Age:
    67
    500
    Feb 11, 2013
    Canada
    I think I have figured out what has happened. As I mentioned I swapped the rectifier and 6Y6 GT with good tubes and it made no difference so I put the original tubes back in.
    Well this morning I turned it on and when I wiggled the rectifier (as recommended by Randy 99CL) it blinked on. So I pushed it with a chopstick so it would stay lit and the volume came on.
    Will discharge the caps and clean retension the tube sockets.
    I just ordered two 3 prong cords with 9 foot cords. Time to properly ground the Vibro Champ and Champ. Will be sure to clip out the death cap.
     
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