Tube Amp Archive

hi again checked all resistor values and changed 3 2x 100k and 1x the 220k fixed also one loose ground connection kept the 560ohm cathode resistor now i got other values cathode - plate voltage is now 408v and 25.5v over the cathode resistor much better but still power dissipation about 120% guess n...

thanks
we didnt check any resistor value (except cathode bias) as we presumed it was correct but apparently not , our bad.
i have schematics and will go through them all
i will place a pic when done , for double check

thank you
the 1.5 k is also 1/2w?

the ground connection of the resistor was disconnected. Now the measuremnt v3 pin 5 is 564k and not 220k
and indeed the resistor is 564k but should be 220k according schematics
on another scheme there is a 1.5k gridstopper resistor which is not present on the board

thanks for the advice
v3 pin 5 and ground gives OL
v3 pin 8 and ground gives 560ohm , as installed
disconnected the nfb but didnt test yet as i want to get the correct value first on pin 5

hi all first time here on the forum As we are rebuilding a Fender vibro champ , a problem came up during the testing. when putting the cathode bias resistor of 560 ohm there was a voltage of about 75v the cathode - plate voltage was 225 to 275 V depending on the tube we installed (all 6v6) with the ...