Filter caps not holding a charge

Hi Guys - Can someone please explain to me exactly how the filter caps in a 5e3 circuit hold their charge? I'm missing something. According to the weber layout, the negative side is grounded on the 3 filter caps. Won't this ground cause the caps to drain when power is shut off?

...but the positive side is connected to essentially nothing. When you shut down the amp and the tubes stop conducting, the only thing that's there to discharge the caps is their own internal leakage. They will discharge over time, but depending on the amp configuration and the component quality, it could be a very long time.

Hi Guys - Can someone please explain to me exactly how the filter caps in a 5e3 circuit hold their charge? I'm missing something. According to the weber layout, the negative side is grounded on the 3 filter caps. Won't this ground cause the caps to drain when power is shut off?

In an ideal capacitor you have no DC current flow from one plate to the other. In reality you have parasitic resistance and inductance that occur due to the way the capacitor is made. You have some leakage current that will flow from the positive terminal to ground, but usually it is not very much (on the order of 10s of microamps and it will decay as the voltage drops). This can cause the cap to take a long time to discharge when you turn the power off.

In older amps you can have some pretty high time constants for the caps to discharge. A lot of newer amps will put a 220kOhm 5W resistor in parallel with the first filter cap so that when the power is turned off the amp will discharge relatively fast.

I've worked on old amps that will self-discharge in a few seconds, but I've also worked on ones that have been off for days and still had lots of voltage on the caps. If I remember correctly there was some talk at one time about caps "remembering" what voltage they spend their life time at, and that they can recover this voltage even after being turned off for a long time.

Can't recall who did the video on YouTube but turning off an amp that is hot will drain the caps pretty much down to nothing in short order. The heaters are still hot and the bias current for the output tubes keep flowing out of the caps even if the switch is off. Now if you turn the amp on and turn it off again without letting the tubes heat up, the caps will hold a charge for a while.

Thanks guys - that answers my question....but here's another. If a capacitor goes bad, what will that do to voltage? Will it go up or down? For example, if I'm expecting 5 volts on one side of a capacitor, and I'm getting 50 volts instead, would that indicate that the capacitor is bad?