Good evening,
I have an SSE that is about 6 years old now. Recently it started red plating one power tube, does not take very long after turning on to blow the fuse. I have tried the obvious things such as a new tube, put in a new coupling cap, and replaced the bias resistor. Unfortunately it is difficult to get readings with the multimeter because the fuse blows pretty quick after start up, maybe 15-20 seconds if cold. Any suggestions of possible causes are greatly appreciated, thanks!
I have an SSE that is about 6 years old now. Recently it started red plating one power tube, does not take very long after turning on to blow the fuse. I have tried the obvious things such as a new tube, put in a new coupling cap, and replaced the bias resistor. Unfortunately it is difficult to get readings with the multimeter because the fuse blows pretty quick after start up, maybe 15-20 seconds if cold. Any suggestions of possible causes are greatly appreciated, thanks!
One option is to disconnect the power, remove the output tubes, and measure the resistance from each pin to ground, comparing between the channels. There is not a lot that could be at fault, have you checked the grid bias resistor? If that has been open circuit then that can have an impact.
Lift one end of the coupling cap that feeds the glowing tube and test. Remove the cathode bypass cap (or disconnect the wire at the terminal at the rear of the board) across the cathode resistor for the glowing tube and test. If either of these caps are leaky, shorted, or breaking down when powered, the tube will draw excess current and red plate.
Awesome, thank you both so much for your replies!
Will test and post back. I really love this amp, looking forward to having it up and running again.
Alex
Will test and post back. I really love this amp, looking forward to having it up and running again.
Alex
Been a ridiculously long time but finally getting back to this. So to double check I understand, C12 is the cathode bypass capacitor, and I have the option of lifting it or disconnecting the jumper wire on the back of the board? Do one of the two and see if tube is still redplating?
I already replaced the cathode bias resistor (r17) so don’t think that is the problem. Thanks!
I already replaced the cathode bias resistor (r17) so don’t think that is the problem. Thanks!
So I went ahead and disconnected the jumper wire at the back of the board on the problem channel. No redplating, when disconnected. Does this mean it is most likely the c12/22 capacitor that is the problem? Thanks in advance!
Alex
Alex
Ok, got into this a little more. R27 cathode bias resistor was reading around 1 ohm in line on the board. Pulled the c22 capacitor off the board and now getting a resistance of 530 ohms from the R27 resistor. I honestly wish understood this circuit well enough to know what this means.
If the capacitor that you removed still measures in the less than 100 ohm range, it is dead. Make sure it was installed in the correct direction. Or more importantly, make sure the new one is installed correctly. Check the cap in the other channel too. The negative lead faces the rear of the board.