5E3 crapped out. Anything I should check?

Discussion in 'Glowing Bottle Tube Amp Forum' started by David Meiland, Jun 26, 2021.

  1. David Meiland

    David Meiland Tele-Meister Silver Supporter

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    I picked up a used Fender '57 Custom Deluxe. Initially it sounded great. After some playing time I found that at moderately loud volumes I'd get a bit of a farting/sputtering sound if I hit low notes. Not every time, but sometimes, and it took a while to warm up to the point where it would start happening. My first thought was that the vibration of the speaker was impacting one of the tubes, and the tube was getting ready to fail. It was an electronic sound, not a mechanical one.

    I had preamp tubes on hand so I changed those. No improvement. Still sounded great, still made the occasional noise.

    I ordered power tubes and put those in this evening. It sounded great at first but after maybe 10 minutes of playing it suddenly fizzled (an actual fizzle sound that lasted maybe a second or two) and now it's dead. Grasping at straws so I put in a different rectifier tube.... nothing. All the tubes are glowing. There are three fuses that I can see, and they are all intact.

    If I had more tubes I might put them in, but I don't. Wondering if there's any way for a newbie to do some preliminary investigating with a multimeter, see if maybe I can avoid a trip to the doctor. The doctor is some distance away and I'd rather play this thing than be without it until I can get it there.
     
  2. J. Bonkosky

    J. Bonkosky Tele-Holic Silver Supporter

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    https://robrobinette.com/How_The_5E3_Deluxe_Works.htm scroll down a bit and you will see a layout with voltages in red. Your voltages should be close to them. Remember you secure your black lead to the chassis put you hand in your pocket and use the red probe in the free hand. Good luck.
     
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  3. kbold

    kbold Friend of Leo's

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    I would check that the high voltage filter capacitors are still capacitating.

    Pikkies may help.
     
  4. dougstrum

    dougstrum Friend of Leo's

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    Look for a cold solder joint~
     
  5. corliss1

    corliss1 Poster Extraordinaire Platinum Supporter

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    Are you familiar with taking high voltage readings while the amp is running? If not, you'll either need to do some homework before opening it up, or take it to a tech.
     
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  6. Wally

    Wally Telefied Ad Free Member

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    Anytime an amp’s sound changes…even if it is for the better….one should observe the tubes while playing..especially the power tubes.
    Tech time, imho.
     
  7. pinchegil

    pinchegil Tele-Holic Platinum Supporter

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    learn how to discharge the filter caps before you open the amp, then post this on the shock brothers forum
     
  8. David Meiland

    David Meiland Tele-Meister Silver Supporter

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    OK, did a little reading and discharged the big blue filter caps. After discharging them I put my meter across each one and got 19 on right right, overload in the middle, and 15.9 on the left. Then I turned the amp on, took it off standby, and measured the voltages at the positive end of each cap. Got O on the right and middle, and 547 on the left.


    5e3.jpg deluxe.jpg
     
  9. David Meiland

    David Meiland Tele-Meister Silver Supporter

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    Done
     
  10. corliss1

    corliss1 Poster Extraordinaire Platinum Supporter

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    So you have the black probe on the chassis/ground, and you're getting zero volts on BOTH the filter caps?
     
  11. David Meiland

    David Meiland Tele-Meister Silver Supporter

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    Correct. I was thinking the middle one was going to be the problem and I don't grasp how there could be no voltage on the + end of the right one since it seems to measure close to spec for capacitance.
     
  12. corliss1

    corliss1 Poster Extraordinaire Platinum Supporter

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    Do you measure any resistance across the resistor between left cap and middle cap? The number could change because your meter will slowly charge the cap, but that's the next thing to check.
     
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  13. David Meiland

    David Meiland Tele-Meister Silver Supporter

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    The right hand resistor shows 22k, the left hand shows a moving value with 3-4 decimal places.
     
  14. corliss1

    corliss1 Poster Extraordinaire Platinum Supporter

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    Okay, so we have voltage on the left side of that resistor and none on the right, correct?

    Lift one end of the resistor, doesn't matter which, then measure resistance again.
     
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