Crate V5 - very low volume

[Aerostoon]

Did you measure across R18? If you did, and got "no voltage", then I suspect if you power off and remove the circuit board, you will find R18 is failed open. This is assuming you probed the actual leads on R18 while testing. I find it hard to believe that a 3W resistor would burn up, but then why did they make it 3W? Outrageous.

I don't know if it's possible that the screen is actually grounded out and not causing horrible secondary effects; haven't seen that one yet.

You are looking for an open circuit path where there should be continuity (or appropriate resistor value). Do your continuity checks and verify what's really connected to what, and where the open circuit is.

I removed R18 from the circuit board and it is open. When I bought the amp I got it for a low price because it didn't really have any volume. You could turn it up to 10 and talk over it. I haven't seen a resistor like this fail before. It looks just fine from the outside. I will put a new one in and hopefully it fixes the problem

[eschertron]

Do you happen to know if the EL84 was replaced at some time in the troubleshooting process? I'm still trying to figure out how R18 could have over-currented (is that a word?). P = I^2*R, so the failure current would be SQRT(3/470) = 80ma. If that's how it failed, I'd think it had to take the tube along...

Maybe get two resistors just in case

[Aerostoon]

I am not sure if the EL84 was replaced before I bought the amp. I found a resistor available at our local electronics supply store. It's a 5 watt instead of the original 3 watt.
NTE 470R 5 WATT POWER WIREWOUND RESISTOR 5W147

Hopefully they have one in stock

[52 Bill]

A 5 watt resistor will work fine as a replacement, as long as there is enough room to fit it on the board.

Screen grid resistors open up all the time. The usual reason is the power tube that it is connected to draws too much current. You should check the EL84 before using it with the replaced resistor.

[Aerostoon]

I put the new resistor in and the amp works great thank you everyone that helped with the troubleshooting!!