Fender Ultimate Chorus amp hums badly on lead(distortion)channel

[Ray_071]

I just bought a fender ultimate chorus amp(2x12" speakers-130w's RMS-solid state-used but in great condition), and I've noticed it doesn't hum at all when the guitar cable and guitar are not plugged in, but when the cable and guitar are plugged in; the normal channel hums very little(hardly noticeable) but the lead channel hums pretty bad. I use a fender squire vms, but the interior of the guitar is shielded. I was wondering if this is normal for a solid state amp, and if it isn't what could be causing this? It also makes a loud popping sound when I turn it off while still on lead channel, I end up switching to norm channel before I turn it off...

[J M Fahey]

Hi Ray: short answer: the hum comes from your guitar. The clean channel doesn´t bring it forwars very much, but the hi-gain channel shows it in all its beauty. If the hum all but dissapears when zeroing your guitar´s volume pot, that´s it
Just to make sure, short a plug , insert it in the amp input and switch channels.
Very probably you´ll have very little hum, only hiss.
Bye.
PS: if (very unlikely) your amp hums badly, then you have anther problem. Filtering ... internal grounding ... Hard to tell without seeing the amp.

[Enzo]

OOr, if it doesn;t hum with nothing plugged in but does hum with a guitar.  The input jack may have lost its ground connection - specifically the sleeve connection to ground.  The tip shunt will still work and silence the empty jack, but plug any signal source in and no ground.  You'd only hear hum with a cord plugged in.