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EF86 voltages


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2/20/2000 3:14 PM
Ian EF86 voltages
For the first gain stage in my amp, I copied the EF86 circuit from the Vox AC15 schematic.  
 
The screen grid voltage is about 10V higher than the plate voltage (110V vs 100V). I've never used these tubes before, is this normal? The Vox schematic only has the plate voltage.  
 
The amp sounds great, but am I doing any harm?  
 
Thanks,  
Ian
 
2/20/2000 5:19 PM
Ken Gilbert

no, you're not causing any harm.  
 
what is the screen resistor value, by the way? you can determine the total screen current by the voltage drop across this resistor.  
 
kg
 
2/20/2000 11:29 PM
Ian
1 meg & it's drawing 0.21mA. Normal?  
 
Thanks,  
Ian
 
2/21/2000 3:06 AM
Ken Gilbert

sounds good to me... i'll bet you're pulling about 2 mA through the plate. that's a rule of thumb--that screen current should be about 1/10th of plate current.  
 
kg
 
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