Madamp G3 - wrong measurements, weird sound

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    • Madamp G3 - wrong measurements, weird sound

      Hi there, I would like to ask for a help and assistance.

      I measured totally wrong voltages inside G3. I hate to say it, but by my unfortunate mistake I caused a tiny spark/short on V1-1 when I started to measure :(
      Could you help me to troubleshoot please? Thank you for any help,

      Janek D.

      I UPLOADED SOME Additional photos (inside the amp and measurements table)


      No.CheckpointShould beIsComment
      1Wall plug socket*230 VAC235Power Supply input voltage at start of measurement
      2V3-4/56,5 VAC6Heater voltage at tube socket V3 - between Pin 4 und 5
      3BR1- ~/~208 VAC212Input of bridge rectifier BR1 - between the two "~" lugs
      4(A) lug 21 t **260 VDC320Supply voltage to V3
      5(B) lug 18 t237 VDC317Supply voltage to V2
      6(C) lug 18 b225 VDC315Supply voltage to V1
      7V1-1225 VDC315At plug socket
      8V1-381 VDC237At plug socket
      9V1-6105 VDC296At plug socket
      10V1-71,2 VDC0At plug socket
      11V1-8110 VDC0At plug socket
      12V2-1185 VDC308At plug socket
      13V2-350 VDC0At plug socket
      14V2-6166 VDC312At plug socket
      15V2-83,0 VDC0At plug socket
      16V3-1251 VDC321At plug socket
      17V3-6254 VDC321At plug socket
      18V3-3+810,5 VDC0 / 0At plug socket, please measure at both lugs!
      19(R13) lug 10 b47 VDC0an R13 unten
      20Wall plug socket*230 VAC236Power Supply input voltage at end of measurement
    • Hi Janek and welcome to the forum. When you measure 212V AC at the input of the bridge rectifier, the absolut maximum DC voltage you can get is 299V DC (w/o any load and ignoring the diode voltage drop). So how are you measuring your DC voltage? Besides measurements 1-3 and 20 all of them need to be measured with setting "DC" and against ground. Is your ground correctly connected as set out in the manual? A general hint: if supply voltages (4-6) are way to high and cathode voltages (e.g. 10 and 15) are 0 there is no current flowing so most likely there is a wrong wiring or bad soldering in the power supply circuit, please double check that...
      Regards,
      Martin
      ========== MAD = Martin Adams / Digital ist nicht alles / madamp.de ==========
      ========= Meine Alben: musikding.rocks/index.php/AlbumList/6475/ ========
    • Hi, I apologise for the delay. Thank you so much for your answer!

      I have not found the problem yet. I checked all the connections and measured the voltage again with a multimeter set to DCV (1000), I tried another multimeter and got the same results posted above.I tested the amp with a 8 Ohm amp and without a guitar connected to the input.

      In the end I couldn't resist and plugged my guitar in. The amp worked just fine until the tubes warmed up (lightened up), then the sound started to disappear.

      Could you recommend me, please, how to properly measure a wrong wiring in the power supply circuit? What should I look for?

      Thank you in advance for any recommendations, I really appreciate your insight.

      Cheers

      Janek