• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

What's been broken?


2004-09-14 1:29 am
I had inadvertently touched the one lead of power transformer and the ground lead at the power socket and suddenly the house fuse jumped but the amp fuse not broken!. When I reconnet it, the amp when silent on one channel and half volume at the other. I measured the pin 8 of the cathode of the power tube n found drawing less than 10% current it usually draws (6550 0.3v much less than this!). HT supply is normal, resistance measurement of the output are all the same for the 4 tubes legs including the screen legs, what is the problem? Is the opt failed?
My God!:bigeyes:


diyAudio Moderator Emeritus
2002-10-24 10:19 pm
Probably not. Use an ohmmeter to check primary resistance of the OPTs. If the primary resistances are the same for both channels and there's no short between primary and ground, your OPTs are likely OK.

While you're at it, check the resistance between output tube cathodes and ground. You might have lost those resistors.