Voltage problem on a Boogie 20/20 power amp

[Donzap]

Hi ppl, I have some kind of issue on a 20/20 power amp. I sold it some weeks ago and worked fine, but now the new owner has come with some resistors burnt. That resistors are the known 330ohm 10 resistors in the power supply.

I have changed them and made some measurements in the power supply section and the voltages and much higher than in the schematic. In the schematic shows 390V, 326V and 242V in A, B amd C. And I have measured 461V, 460V and 450V I have tested all the resistors and diodes and are ok, and changed caps and the same readings, The tranny is working fine, and I have 330VAC on its secondary.

I sold it quite cheap and I have some electronics knowledge, so I wanted to fix it by myself.

Any ideas or advice?

Thank you very much and sorry for my poor English.

Angel.

 

[crane]

Your voltages reading looks like there's no tubes plugged in.

 

[Donzap]

Your voltages reading looks like there's no tubes plugged in.

Right, Shall i plug them to make new readings? I am afraid od lose them if something it's wrong.

Thank you very much for your answers.

 

[crane]

Sure, without the tubes voltages are really higher !
330VAC x 1.41 = 465 VDC, that's what you read without tubes (the 10-15V drop comes from the circuitry consumption).
With the tubes plugged in Voltge should drop to the values written on the schematic, due to the tube's consumption.

BTW 390V is too much for a standard EL84. I know Mesa select their tubes, but a failure can happens sometimes at this voltage. So a faulty tube could have caused the resistor to fail.