Output tubes were replaced, now weird stuff happening

[GuitarEvan07]

Regardless, I'm going to bring the amp back in where i got it repaired.

I have a Marshall JVM210H, and the electrician blew my output tubes on my amp when trying to fix something. Got the amp fixed, but I noticed a few things were different after the repair that didn't happen before:

1. Amp makes a loud pop when turning on standby(muting sound).
2. Sometimes it hums randomly even when guitar cable is unplugged. Will go in and out of humming even when the guitar cable is unplugged. I can make a video and show you all if you are puzzled too.
3. None of this stuff is consistent. I haven't figured out the pattern yet, but I really don't know what to do.

I guess I'll just bring the amp back in and tell the guy whats up, but I just wanted to know what your opinions are on it so I'm armed with as much information as possible.

[IbanezFreak777]

The deal with Tube amps, is that you either know what your doing, or you really just dont. I fall into the I dont, and just prefer to take it to my guy. I suggest you find yourself a Guy.. Meaning a guy who knows his stuff and you stick with him for life...

Obviously your going to take it back, and I would just tell the guy the issues, maybe write them down so that when your speaking to him you dont miss any details.. Then just tell him, just fix the issues...

Cheers and good luck..

[SonicProvocateur]

Sounds like dying screen grid resistor. -these are often damaged after a power tube failure.

You need to have a good Marshall technician look over your amp (that actually has JVM schematics and load numbers) and check over all the caps and resistors. Something is definitely leaking or dying. If you don't get that fixed soon, your amp may die again (believe me, i've had similar problems.)

[racerevlon]

^ +10

What Sonic said. Sounds like either a resistor or cap went bad along with your tubes. A bad capacitor discharging could account for that loud POP sound you're hearing. Leave this one to the pros unless you have a degree in Electrical Engineering and the Marshall schematics...

Cheers,

Race