M15mk1 manual step 2.6.2: r23 smoking on power on

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    • M15mk1 manual step 2.6.2: r23 smoking on power on


      being a first time builder of a tube amp kit, I already run into problems. After building the pwr supply brd and applying power to the power transformer only, I measured 7.4 V on heater side, 257 V on the power side, also completely in range. This is step 2.6.1 in the manual.

      Then I connected the pwr supply board on step 2.6.2 in the manual and reapplied power. R23 started smoking so I turned off power immediately. Checked soldering, value of all components (did this with multimeter also before soldering). I can not see what’s wrong. Can anyone advice? Answers may be in german as well in english.

      thanks :)
    • Hi and welcome to the forum!
      So you connected the power supply board as described in chapter 2.6.2 ("secondary side") and measured the voltages as described in there, correct? (Your chapter numbering in your post is not what I find in the current manual version 2.5, that's why I'm asking ...).

      If yes and R23 starts smoking (but R16 is fine) when measuring w/o tubes but everything connected, you have a problem at V3 (too much current going through R23, but not through R16). Please double check the wiring and the component values (e.g. C18?).

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    • hi,
      thanks martin for your support. Luckily I found out what was wrong. I measured the resistance between the common point r18 and r17 and ground, it was nearly 0 ohms. ?? No wonder why there was a high current running. So I rechecked everything and found out I made a mistake in the beginning: I soldered ALL lugs to ground... I watched the picture on top of page 10... so it all comes down to RTFM and read the layout plan....

      by the way the revision I received was 2.5. There are some corrections to be made, like the connection numbers on the transformers I received (askjanfirst) do not match the numbers as stated in the manual. I will keep you posted. So far it has been great fun!