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Proluxe Problems - New build

Discussion in 'Shock Brother's DIY Amps' started by Baron13, Oct 27, 2020.

  1. Baron13

    Baron13 TDPRI Member

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    Hi, working through my Boothill Proluxe build. Made it through startup...almost.

    The bias is super low at 19mA. If I measure the pot, I get -37 on one side and -58 at the other. That seems right, but with a bias probe hooked up the meter reads 19 at the highest.

    Also no sound. I get the static as I probe through the speaker but no guitar.

    Now my B+3 is low. At first I read 402/368/266

    Now I get 426/347 and only 19.

    Rectifier gets 5v heater and 320 on pins 4 and 6

    V4 heater 6.4
    Pin 3 423 Pin 4 347 Pin 5 and 6 45.4

    V3 heaters 6.4
    Pin 3 423 Pin 4 346 Pin 5 and 6 45.4

    Preamps look problematic.
    V2 had 176 on Pin 1 now only 18
    Pin 2 0.5 Pin 3 0.19 heaters 6.4
    Pin 6 had 218 now only 19
    Pins 7 and 8 0.3

    V1 pin 1 19.2. Pin 2 0 Pin 3 11.9 Heaters 6.4 Pin 6 11.8 Pin 7 19.3 Pin 8 11.9

    Any ideas on where to start?

    Thanks
     
  2. BigDaddy23

    BigDaddy23 Tele-Holic

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    Confirm your voltages from the 3rd filter cap (ie the 266vdc) are actually getting to the plate resistors. You may have a jumper connection problem between the two points. Having 11.9vdc on the cathodes of V1 is a bit odd as is the pin6 reading on the power tubes. Check you have negative (bias) voltage at the junction of the two 220k resistors that feed the coupling caps in the output section. I would also go back and trace the wiring against the schematic to confirm all your connections.
     
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  3. D'tar

    D'tar Friend of Leo's

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    Something is either poor connection or unintentional connection to ground.

    Assuming the vdc on v3,4p5 is -ve (-45)?

    A few photos may help
     
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  4. Baron13

    Baron13 TDPRI Member

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    I will reflow some suspect areas and check on the above mentioned areas tonight. Thanks! I will add photos.
     
  5. Baron13

    Baron13 TDPRI Member

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    Got it running! Reflowed some iffy joints and got 286v back on the B+3.

    Temporarily took out a impedance switch.

    Found a bridge between the 68Ks and the 100ks.

    Bias is still a bit low at 31mA for 403 plate voltage. I’ll work through that some more tomorrow.
     
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  6. Baron13

    Baron13 TDPRI Member

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    Location:
    Long Beach, CA
    I brought the 39k resistor on the bias circuit down to 27K. Now I can get it into range. Left it between 60 and 70%. Sounds good. Survived a three hour rehearsal so I think I’m in good shape.

    I am planning on a Weber 15A150A but I have it running 2x10 now(10F125). Hmmm. 2x10 or 15?
     
    robrob and BigDaddy23 like this.
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