Cat Sir,
You may consider the following:-
First of all, test all the power tubes(KT88) if you have a tube tester. Or move the power tubes (Push Pull?) in Channel L to Channel R and those in R to L. Yes, I mean "swop". If the OPT Transformer still gets hot, the problem should not be with power tubes. OPT transformer gets hot because too much current passing through. Does the plate of the power tube turn to red (burn) gradually? Should this be the case, you have to check the value of the Cathode Resistor(s) if it is self-biasing designed or the negative voltage supplied. Another factor causing the plate current increased would be with the coupling-cap, the one between driver tube and power tube. The main function of a coupling-cap is to block d.c. When leakage occurs, B+ at the driver stage would go through it into the power tube making the current increased. So, check that capacitor by using a capacitor checker. If not, "swop" again with the one in another channel. In case the plate of power tube does not turn red and the plate voltage of all the power tubes is normal, then swop the OPT transformers. By then, you should know if the problem is with the transformer. |