Plate voltage drop in a Super Lead

[Afterall]

No, I got one that reads mA. Not, to confuse thing but I have the same issue with a jcm 900 4500 where I couldn’t get to the targeted adjustment on the bias pot. (No voltage drop or blown fuse with this amp)

 

[Afterall]

So, I got a new fuse in and I’m back to the 440v plate voltage, I biased it a little cold 36ma vs 39ma, but the amp still sounds crappy, as if the guitar is out of tune, especially the higher strings (line there’s phase cancellation). I’ve tried other guitars, cables, speakers. Any thoughts?

 

[mickeydg5]

Find a decent tech in your area.

 

[Pete Farrington]

A HT cap at the reservoir or screen grid nodes may have failed.
That would cause reduced voltage, decreasing anode current, and the AC ripple on the HT would modulate the signal at high power levels.

 

[Afterall]

I also failed to mention there is some hum present and when switching into standby there is a loud buzz that slowly fades out.

 

[Afterall]

Just to close out this thread. I found a local tech who discovered a loose resistor connection, he soldered and the amp sounds as it should now.

 

[rtcook]

Out of curiosity, what resistor was the problem?