Trouble with my blues junior

[cpechous]

So the other day my blues junior started shorting out, so I checked the power tubes and one of them had a burn mark on them, the GT EL84's. So I went to pick up 2 new ones today...I put them in and i can hear sound coming out but it feels like its not fully powered up. Has anyone here had a similar problem, etc?

Thanks

[cpechous]

also when i crank it up, the power tubes get really really hot, so I am not even going to mess with it anymore.

[Garydean]

Are the output tubes plates, turning orange? Where was the burn mark? Any carbon traces on the output sockets. You may have to rebias your amp now that you have a new set of tubes.

[cpechous]

Yeah the tubes are lighting up, thinking I have to get take it in for it to be biased or whatever, I have a 5 year warranty on it so i'm not that worried about it.

[ajeffcote]

Lighting up?Glowing a little or glowing cherry red?The tubes will get very hot when everything is alright.I don't think your BJ has a bias adjustment,so a bias pot will need to be installed.And it has a PC board with delicate traces so care must be taken.Search for Bill M mods for your BJ,you'll see a lot there.

[WholeToneMusic]

Blues Jr

Just an idea-

The Blues Jr runs very hot. Bad design on Fender's part. Make sure the new EL84's you use handle close to the same plate current as the old EL84's.

Best Regards,
Brian

[bnwitt]

the first thing I would do would be to check the screen and grid resistors for the power tubes. They are R20,R23,R24 and R25. Make sure they are not burnt. If you have a mulitimeter and know how to drain the filter caps you can check them for proper value with the amp unplugged and drained of all power. R24 and R25 should be 100ohms. R20 and R23 should be 1.5Kohms. They are located on the main printed circuit board above the V4 tube socket.

Then with no power tubes in the amp I would check pin 2 of both power tube sockets for the -10.7 volts DC bias voltage. Pin 2 will be the second pin from the keyway going counter clockwise looking at the tube side of the socket.