Laney amp blew but both fuses didn't.

[BeerBaron]

Standard day, playing guitar really. Let the thing warm up, turned it on and just started playing around and jamming. I go to retune and as I do, I see the V1 and possibly the V2 tubes pretty much give a wicked blue flame and pretty much sounded like a sparkler, coming from the speakers.

 

I immediatly switched both switches off and unplugged it from the wall. All done within 5 seconds of them blowing.

 

Gathering myself, I take off the rear cover and inspect the insides. The tubes look okay, but on both of them, I see that I guess over the time, they have developed a brown ring around the top of them. I am thinking possibly an incorrect bias, which made the tubes wear out extremely quick. I bought this amp about 5 years ago, stupid as I was when I was a kid, thought it was the **** best to have a tube half stack. But in that time, I have maybe cranked this amp full out, maybe 10 times and that lasted only for a couple minutes. I was playing at around 3 out of 10 today.

The scary part of it all is, that both fuses HT and Mains fuse did not blow. I am thinking, maybe because I caught it in the nick of time, switching it off and unplugging it, before anymore serious damage could be done.

 

What do you all think? Also, which EL34's do you think I should replace the now shot ones? I am going to go with a full quartet replacement of course. 

[HKSblade2]

Replace the tubes but dont count out any open screen resistors or other problems that could have occurred.

[guitarcapo]

Make sure the current rating for the fuse(s) is the recommended rated value for that amp and not higher (the "A" number)....even if the fuses were from the "new" amplifier. I've seen cases where the fuses where replaced with the wrong ones at the store or even the factory. If you keep blowing fuses, a component is fried out.

[BeerBaron]

So, I took the chassis out of the head today and did a general inspection for anything that might have malfuntioned.

 

I had taken this amp in for cutting out one other time, the tech found a Resistor that's solder had broken for some reason. I just found out which one it was and the job he did. 

 

 

A pretty amature one in my opinion. Although it doesnt look as though that could be the problem. No leaks or anything from anywhere else within the amp. The internal fuse on the amp, also has not tripped.

 

So I am just thinking that the tube(s) genuinely malfunctioned. I'm gonna call a few techs today to see how much an install/bias job would be. I'm going to be buying my own tubes of course and bringing them and the amp for the repair. 

[t_e_l_e]

i had a similar issue with my sovtek midget50

cause i never saw the blue glow and feared something serious could be damaged i switched it off and took it to a tech

 

came out, the glowing tube lost its vacuum and oxygen made it inside, which made it glow blue.

silver thing on the top of a tube is mercury and it should "eat up" any rest of oxygen. but if the glass breaks even just a small crack, more oxygen comes through which the mercury cannot deal any more.

 

all what was needed, was just to replace the tubes, yeah the tech also fixed some pad input sockets and stuff which was good to do but had nothing todo with the broken tube

 

check your tubes, if instead of the silver shining mercury on top you have some white stuff there.. thats the definite sign that air came into the tube