What would cause low plate voltage?

[6AM]

I just got an amp that I knew wasn't working. I was hoping it was bad power tubes, but no such luck.

For some reason there is only 190 on the plates. It should be 475 on this amp. What would cause this? Bad OT? Bad electrolytics (the amp was in storage for 5 years)? :confused:

[TheAmpNerd]

Originally posted by 6AM
I just got an amp that I knew wasn't working. I was hoping it was bad power tubes, but no such luck.

For some reason there is only 190 on the plates. It should be 475 on this amp. What would cause this? Bad OT? Bad electrolytics (the amp was in storage for 5 years)? :confused:

I don't know.

HOWEVER

We can figure it out. Start with the each leg of the power tranny and read them...then the reciifier/diode, read them.
Then read the voltage before and after the choke.

Which are low?

[VaughnC]

Could be one of several possibilities....but it sounds like a power supply problem. It could be the transformer, rectifier(s), or the electrolytics....all of which can be checked if you know your way around electronics. However, could the power transformer primary have dual voltage windings? If it were wired for 240v and you're connected to 120v, that would explain it. Or the mechanism used to switch between 240v & 120v could be defective. Or a bad on/off or stand-by switch (they can develop internal resistance). Or something as simple as a bad solder joint. Many possibilities.

[6AM]

It's solid state recitified.