Hello everyone, it's been a while. I did try to use the search function to get an answer to my question but the results were rather bloated and couldn't really find what I was looking for. Basically, I had a really long practice session (about 6 hours) and toward the end my Ampeg SVT CL went into fault mode (red green flashing light). One of the tubes in the back is no longer glowing when I power it up. I read somewhere that blown tubes will still glow? Is this most likely a bad tube or could it be something else? I'm going to take it to a tech but wanted to get some advice beforehand. I don't really know any well known techs around my area (Detroit Metro) so I just kind of take it to whomever I can find, which is why I would like to be informed before going in. If this is a tube problem, can anyone recommend an affordable set of tubes? The last time I took my head in (about 2 years ago?) the tech said that both sets of power tubes were really wore and about to go out. I didn't end up replacing the tubes, but should I replace both sets this time if thats the case? Or keep one of the worn sets with a brand new set? Thanks for any advice!