I am trying to build a 18w amplifier based on this schematic however my power transformer doesn't have a center tap on the secondary winding

Is it possible to use this power transformer for this project? I also tried it using a solid state rectifier (the one with 4 pins: - AC AC +) connecting the ac to the transformer the (-) to ground and the (+) to the standby switch (please see the schema), although I could measure the correct voltage on the (+), there was no current going on the grids of the tubes, not even on the filtering capacitors.

or maybe the problem is somewhere else in the circuit? appreciate your help

  • \$\begingroup\$ That "220K 1W" resistor looks like a problem. Was it meant to be 220R? \$\endgroup\$
    – user16324
    Jul 12, 2015 at 21:36
  • \$\begingroup\$ wow, I just created a new question :), where I was suspicious about that 220K resistor. electronics.stackexchange.com/questions/179877/… please paste your answer to it so I could mark it as correct answer :) \$\endgroup\$
    – Sarkipinty
    Jul 13, 2015 at 9:41

1 Answer 1


That is not a schematic.

Yes, you can use it, with a full-wave bridge rectifier. Instead of grounding the (nonexistent) center tap of the transformer you ground the minus side of the bridge rectifier.

Similarly one side of the filament should be grounded rather than the (nonexistent) filament winding centre tap.


simulate this circuit – Schematic created using CircuitLab

Be extremely careful and don't electrocute yourself.


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