.50 caliber + head problem with tubes.

[Pzorch]

I don't know much about tube technology or tubes amps other than I like the way they sound, so bear with me.

I recently changed tubes in my .50 caliber + head. When I bought it, it had sovtek 6l6's in it so that's what I replaced them with.

I was told it is fixed bias so I can just pop them in and start playing. I was also told by another player(and someone who's opinion I would trust on the matter) that I should let the head chill on stand-by for a few moments before I started playing.

So when I put the tubes in and turned it on, I failed to notice that the head wasn't already in stand-by. And for just a SPLIT SECOND the amp was off standby with it's new tubes. I quickly switched it back, thinking it wasn't going to be a big deal, and let the amp sit in stand-by.

However, when I started playing I knew something was wrong. Only the clean channel worked, even when I switched to lead, it stayed clean and the volume started to peak and sound scratchy when turned it up. I waited a bit, tried again, and this time the lead channel only worked for a split second before changing to clean again with the same volume problems. And this is how it stayed. I did also notice that if I smacked the head hard while it was on that it turned back to dirty for a second, as well.

So what is the deal here? Do I need to get new tubes? Could it be the preamp tubes? The new power tubes don't really look burnt. I know my fuse is fine. Thoughts?

 

[Bugeyed Earl]

Although I don't know what's wrong with your amp, it's very unlikely that you damaged anything by switching it on briefly without the standby switch engaged. How does it behave when you put the old tubes back in?

I had a similar issue with my .22+, only mine would only function in the lead channel (unless I unplugged the footswitch.) With the switch plugged in, when I selected the clean channel, I'd get a second or two of clean, then it would quickly fade over to lead.

My problem turned out to be caused by a higer-than-normal voltage condition on the circuit that handles the switching, and I repaired it with the aid of some good advice from other members of this forum. I think our amps share the same switching circuit, I wonder if you've got too little voltage to engage the lead channel? For what it's worth, I bought my amp in that condition, don't know if it developed that symptom after a tube swap, but I doubt it.