Smokin' Joe II low ouput
Moderators: pompeiisneaks, Colossal
Smokin' Joe II low ouput
Hey guys, I have an amp I built a few years ago, the Smokin' Joe II by Weber...it worked great, never really rocked like it should though. The pilot lamp assembly took a dump, so I replaced that along with a very browned 2.2k off the first filter cap. Now I have no sound unless I turn it all the way up and it just barely comes on and produces sound. I have 325v on pin 7 of the EL84, 10.9v across the 130r cathode resistor. I'm not too familiar with cathode biased amps...i believe I measured 10v on pin 3 of the EL84, my math (which may be wrong) says I should be getting 23.94 watts. I also changed all the tubes to rule out a bad one.
Owner/luthier of Flintrock Guitar Shop, Flint, MI.
Owner of Hawkins Effects Pedals
Owner of Hawkins Effects Pedals
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Stevem
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Re: Smokin' Joe II low ouput
Her is two things you can do to pin down the issue.
1)
Take a volt meter set for ac volts and hook it across pin 2 of each output tube and play full tilt thru the amp, you should see at least 8 volts of drive signal from the amps PI section.
If you do no see that voltage than your issue lies in the PI section, or a preamp section before that.
If you check and report back with the voltages seen on all the preamp tubes plates and cathodes we can likely help you out better at that point.
2)
Get a 1 ohm 5 watt resistor and place it in series with the 130 ohm cathode resistor to ground, hook up your volt meter set for dc volts across this resistor.
This will let you directly read the combined idle current of both tubes, but when you play thru the amp you will see the current go up as the the el84s drive the OT.
Having little output from a known good speaker points to shorted OT.
Please confirm that your speaker is good with a 9 volt battery test.
That 2.2k resistor that burned Up feeds the output tube screens and the rest if the amps preamp section.
The fact that it burned up likely means that one or both of the output tube has a intermittent or full time short, so keep that in mind ,
1)
Take a volt meter set for ac volts and hook it across pin 2 of each output tube and play full tilt thru the amp, you should see at least 8 volts of drive signal from the amps PI section.
If you do no see that voltage than your issue lies in the PI section, or a preamp section before that.
If you check and report back with the voltages seen on all the preamp tubes plates and cathodes we can likely help you out better at that point.
2)
Get a 1 ohm 5 watt resistor and place it in series with the 130 ohm cathode resistor to ground, hook up your volt meter set for dc volts across this resistor.
This will let you directly read the combined idle current of both tubes, but when you play thru the amp you will see the current go up as the the el84s drive the OT.
Having little output from a known good speaker points to shorted OT.
Please confirm that your speaker is good with a 9 volt battery test.
That 2.2k resistor that burned Up feeds the output tube screens and the rest if the amps preamp section.
The fact that it burned up likely means that one or both of the output tube has a intermittent or full time short, so keep that in mind ,
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Smokin' Joe II low ouput
Found wire from V2 disconnected, soldered it up and amp is rocking again! Glad it was an easy fix! It hasn't crunched like this before, all I did was change that resistor and put in some new tubes.
Owner/luthier of Flintrock Guitar Shop, Flint, MI.
Owner of Hawkins Effects Pedals
Owner of Hawkins Effects Pedals