I'd take a look at the fuse(s) as well, especially if the power light goes on when the amp is switched on. Since you have a 4-12 on its way, I assume you didn't unplug the existing speaker cab?
That seems pretty basic, but having a power light, and for no apparent reason, having absolutely no sound when taking it off standby? Ya cant be too careful. Not having a speaker load on an amp when taking it off standby is a quick route to an amp barbecue. 
Fuses tested good, and speaker cab was properly connected. I did get absolute minimal volume from clean channel (so defo connected).I'd take a look at the fuse(s) as well, especially if the power light goes on when the amp is switched on. Since you have a 4-12 on its way, I assume you didn't unplug the existing speaker cab?
This!
100%.
Just remember, Spandex tells no lies. Some of us have become legends here because of it. Others... not so much.
LMAOJust remember, Spandex tells no lies. Some of us have become legends here because of it. Others... not so much.
Can you try it before you leave the shop?
I will next time for sure. Had no reason to not test it, but 100% next time, saves another journey.
And eye liner and mascara. And women’s blouses. If only I could have my 66 years of experience in my 22 year old body. So. Many. Things. Differently!
Cellulite....cough....cough....cellulite
Not yet…
The spandex?
Fortunately Mrs GGJJGG does not frequent this site
