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Hoffman Amps Forum image Author Topic: Fender Blues Jr- one EL84 glowing red hot  (Read 2248 times)

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Offline TerryD

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Fender Blues Jr- one EL84 glowing red hot
« 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

Offline sluckey

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Re: Fender Blues Jr- one EL84 glowing red hot
« Reply #1 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?
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline TerryD

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Re: Fender Blues Jr- one EL84 glowing red hot
« Reply #2 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

Offline shooter

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Re: Fender Blues Jr- one EL84 glowing red hot
« Reply #3 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
Went Class C for efficiency

 


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