Crate BV150HB

[musicman5818]

Hi guys, I having an issue with a Crate BV150HB head, and I'm hoping You can offer some insight. I'll start with some background on the problem. My friend was setting up for a show, and when they were doing a sound check, his amp blew the fuse, He replaced it and tried it again and noticed all the power tubes gradually getting hotter and hotter (took about 1 min.), and glowing bright orange. So I loaned him my amp for the show and we ordered new tubes the next day. Got them from Eurotubes, Nice guy, by the way. So we got the tubes and I set it up for biasing, but upon turning the standby switch off, the bottom of all the tubes were glowing a bright white/blue, and a screeching noise coming from the cab., the heaters looked nice and orange when heating up. So now I'm trying to check the transformers with just a multimeter, and I'm getting some odd results. There are no shorts, but I'm also not finding any high resistant readings from either xfmer. Not quite sure what that means, and if its not in the xfrmers, where do I go from here? and don't say a repair shop please, lol. Thanks

[Twist]

By any chance did you maybe reverse the brown and blue leads of the speaker tranny while you were checking it out? This would cause a loud screaching noise when you took it off standby. The blue glow is normal on tubes. Unfortunately there isn't a way to monitor current draw on that amp while adjusting bias. All it has is a bias voltage adjustment and hum balance. The factory setting is -48 volts.

[musicman5818]

By any chance did you maybe reverse the brown and blue leads of the speaker tranny while you were checking it out? This would cause a loud screaching noise when you took it off standby. The blue glow is normal on tubes. Unfortunately there isn't a way to monitor current draw on that amp while adjusting bias. All it has is a bias voltage adjustment and hum balance. The factory setting is -48 volts.

I did not play with the wiring at that time, so the wiring was stock. The white/blue glow that I'm talking about, is not of the normal variety, it is very bright, and all this happens instantly, the glow and screech that is. And may I add that when I turn the standby switch off the light inside the switch flashes and makes a fizzle sound.

[Enzo]

If all the power tubes were getting red hot, then you most likely lost the bias. See what appears at pin 5 of ALL the power tube sockets. You can do this with the power tube removed.

make sure the new tubes went into the sockets right. Now and then some tubes will fit in some sockets without the guide key lining up.

[musicman5818]

Thanks

Well, here we are. At the beginning I said to myself, it's got to be something stupid, something very simple that I'm overlooking. And..........., sure enough. After tearing it down to all kinds of little parts, and finding nothing. I reassembled, double checked everything along the way. I noticed that the hum balance adjustment was kinda of bent and out of place, so I straightened it out and turned it back and forth with a screwdriver to make sure that it was functional, and went back to reassembling the head. I got everything back together and fired it up. Waiting for the tubes to worm up, wondering what I would find. I pushed the standby switch and everything seemed ok, except for a little hum, so I turned the hum balance counterclockwise and the white/blue glow reappeared, I quickly turned it clockwise and the hum gradually went away. Adjusted the bias and away we go. Wow, a long way to go to make a simple hum balance adjustment. But all is not lost, I did learn a lot in my research, and I also found this forum, and I am greatfull for all your help. Thanks again for all your help and have a great day. Rock on.