JSX problems. Am I screwed?

[Nebulous]

Just got back from the gig. The JSX was fine. Looks like I'll be putting an order in for some new pre tubes. Penta Labs here I come...

 

[drew_drummer]

Heya,

Had the same thing on my friends Marshall DSL100. I've swapped the preamp tubes around, and it's a little better.. but still fucking annoying; and completely ruined the four days recording we had planned!! We're going to replace the tubes and try again; it might need to be rebiased though, something I'm not too sure about doing myself.

 

[Nebulous]

Reading abit between the lines there it sounds almost like you're getting a hum, but still getting some instrument signal through too. Just to clarify, the simptom I had was a loud as fuck hum that suddenly stopped all instrument signal coming through the amp.

Have you tried a power tube swap?

 

[drew_drummer]

I have not, no. You think I should give it a go?

Yes I was getting an instrument signal, but also getting hum - people I've spoke to suspect the preamp tubes. The hum doesn't come in until 10 minutes or so of playing, so maybe it is power tubes.

 

[Wolfeman]

Glad you found the problem.
Yeah screen grid resistors are common things to go, especially on Peaveys. But as GuitarHack said you'd know straight off the bat when turning the amp on if that was the problem.

 

[Nebulous]

Thanks for all the help on this one guys. Even though it wasn't the screen grid resistor that went this time (thank god), it's good to know the symptoms incase it does ever happen.

I have not, no. You think I should give it a go?

Yes I was getting an instrument signal, but also getting hum - people I've spoke to suspect the preamp tubes. The hum doesn't come in until 10 minutes or so of playing, so maybe it is power tubes.

Yeah Drew. If the hum is still there I would definately try a power tube change too, especially if you have some sitting around, it wouldn't hurt.