Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TerryD on March 16, 2017, 04:01:04 pm

Title: Fender Blues Jr- one EL84 glowing red hot
Post by: TerryD on March 16, 2017, 04:01:04 pm

Could this be just the Bias.  How does one bias these PCB board pieces of crap.  Anything else could cause one EL84 to glow red hot when it wasn't before?

The output transformer was spitting blue.  I replaced that and then discovered that by the cord hitting the EL84s all the solder joints were cracked even though they didn't appear to be at first.  I resoldered them.  Now I'm left with a working amp but one EL 84 glowing hotter than anything.

Thanks, Terry

Title: Re: Fender Blues Jr- one EL84 glowing red hot
Post by: sluckey on March 16, 2017, 04:14:58 pm

Maybe you have a bad tube. Maybe the solder joint or board connection for pin 2 is still cracked or broken. Pull the tube and check for negative voltage on pin 2 ON THE TUBE SIDE OF THE SOCKET by inserting a meter probe into the socket pin. What do you have?

Title: Re: Fender Blues Jr- one EL84 glowing red hot
Post by: TerryD on March 16, 2017, 06:07:18 pm

Already tried a new tube in the socket and got the same thing.  How do you check for the negative voltage again?  I get into this about every !/2 a year or sometimes less.  I know I've done it before.  I'll check connections again.  Thanks

Title: Re: Fender Blues Jr- one EL84 glowing red hot
Post by: shooter on March 16, 2017, 08:22:08 pm

Quote

How do you check for the negative voltage again

Quote

Pull the tube and check for negative voltage on pin 2 ON THE TUBE SIDE OF THE SOCKET by inserting a meter probe into the socket pin.

the other probe goes to ground