EVJ head need to be biased?

[rybass]

I've blown two power tubes- JJ and Ruby. JJ within 20 minutes of installation, ruby was a couples days of 30+/_ playing on it. I now have an ehx in and it hasn't blown but it seems to get pretty hot. Only mod made was a standby switch.

 

I didn't think you had to bias EVJ's when changing power tubes. Any comments or suggestions?

 

thanks

[tunghaichuan]

The VJ uses cathode bias which is sometimes referred to as "self biasing." Some people will tell you that you don't need to check the bias in a CB amp, but I think it is a good idea to check the bias of these amps. Sometimes the tube dissipates too much wattage with the stock cathode bias resistor. The voltage coming out of your wall and the B+ voltage also factor into the biasing as well.

 

Here is some info from my site on checking the bias on a VJ:

 

http://www.diycustomamps.com/valvejunior.htm#vjbias

 

tung

 

 

 

I've blown two power tubes- JJ and Ruby. JJ within 20 minutes of installation' date=' ruby was a couples days of 30+/_ playing on it. I now have an ehx in and it hasn't blown but it seems to get pretty hot. Only mod made was a standby switch.

 

I didn't think you had to bias EVJ's when changing power tubes. Any comments or suggestions?

 

thanks[/quote']

[m-theory]

Sounds like you've got absurdly high current. It probably sounds like crap AND is eating tubes. Definitely get that bias under control.