5E3 troubleshooting

Discussion in 'Shock Brother's DIY Amps' started by 26and385, Oct 17, 2017.

  1. 26and385

    26and385 TDPRI Member

    Mar 12, 2014
    Red Sox Nation
    Hey amp gurus, looking for some troubleshooting help on my tweed kit. This is the TubeDepot kit. The kit went together easily enough, I followed all of the start-up checks and got good sound when I did the first power up with tubes. It sounds great and I'm very pleased with the results. However, after a bit of warmup I frequently get a mild pop followed by static that can get progressively worse, sometimes leading to total loss of sound. Usually an immediate power-down and restart will eliminate the issue, but only for another 5-10 minutes before it comes back. My first thought is a heat issue, since I get noise-free sound before the issue occurs. However, I did check DC voltages and have them attached here. My biggest concern is what I believe to be excessive voltage on the filter caps and some of the tube pins. Also, I'm reading 0.0V on pin 7 of V1. I've also poked around with the chopstick to look for bad solder joints, haven't found anything yet. I tried another set of tubes, with a 12AY7 in V1 instead of the stock 12AX7, and the issue remains. Voltage chart is shown below, with both sets of tubes. I can also take detail pics if you let me know which areas you want to see. Thanks in advance for your help!

    V1 JJ ECC835
    1 181.0
    3 1.5
    6 175.0
    7 0.0
    8 1.4
    V2 JJ ECC838
    1 179.0
    3 1.3
    6 218.0
    7 3.0
    8 49.0
    V3 JJ 6v6S
    3 394.0
    4 359.0
    8 23.0
    V4 JJ 6v6S
    3 392.0
    4 360.0
    8 23.0
    V5 JJ 6234S

    Cap1 399
    Cap2 358
    Cap3 275

    V1 Electro Harmonix 12AY7
    1 129.0
    3 2.1
    6 130.0
    7 0.0
    8 2.1
    V2 Mullard 12AX7
    1 165.0
    3 1.3
    6 202.0
    7 2.8
    8 45.5
    V3 Mullard 6V6GT
    3 397.0
    4 353.0
    8 22.0
    V4 Mullard 6V6GT
    3 396.0
    4 352.0
    8 22.0
    V5 Mullard G234

    Cap1 404
    Cap2 352
    Cap3 256
  2. corliss1

    corliss1 Friend of Leo's Platinum Supporter

    Sep 13, 2008
    Lansing, MI
    Looks like you're using a GZ34 rectifier instead of the standard 5Y3. Was this a conscious choice? That would explain higher-than-expected voltages.
    clintj and D'tar like this.
  3. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    The only thing that jumps out on your voltages for me is the phase inverter grid. Make sure thats a 1M grid leak.

    A NOS 5y3 is a good thing IMO.

    What does your 6v6 cathode resistor measure?

  4. FenderLover

    FenderLover Friend of Leo's

    Jun 11, 2009
    Don't worry about pin 7 V1. It should be zero.
    Pin 7 V2 cannot be measured directly with any accuracy. Pins 6 and 8 look good, So I wouldn't worry about pin 7.

    I'd swap your rectifier tube. Do you have another amp you can grab a tube from? Aside from that, check for loose connections.
  5. Nickfl

    Nickfl Tele-Afflicted

    May 24, 2016
    How good are you soldering skills/ how likely is a bad solder joint? It kind of sounds like a solder joint that is ok until it gets hot.

    Chopsticking won't necessarily reveal a bad solder joint, sometimes they seem fine until you pull on them with needle nose plotter an then they break. You should be able to pull on the joint pretty good without it beaking if it's done right.
  6. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    It does sound like a bad solder joint. Poke all the solder joints with a chopstick with the amp up and running. You could even have a dry eyelet (no solder).
  7. Fiat_cc

    Fiat_cc Tele-Holic

    Oct 8, 2016
    Melbourne, Australia
    Not that it will likely have any relevance to the outcome here, but I’m curious about why you left pin 2 out if all of your preamp tube voltage readings?
  8. Commodore 64

    Commodore 64 Friend of Leo's

    Mar 1, 2010
    Kent, OH
    Been there done that. Probably a solder joint somewhere (or dry eyelet) as robrob mentioned. I've had both!

    Similar symptoms. Both time were filter caps for me.
    Last edited: Oct 18, 2017
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