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Re: Voltage check


 :
4/29/1999 9:45 PM
Bruce
Re: Voltage check
You have everything you need right there Doug!  
Your measured cathode voltage of 22.2v is across the cathode bias resistor.  
If you used the 250 to 330ohm ones we talked about, then your power tubes are self biased at around 12.5 to 15 watts each right now.  
22.2v/330ohms=67ma or 33.5ma each tube.  
22.2v/270ohms=82ma or 41.0ma each tube.  
33.5ma x 368v (plates)= 12.5 watts.  
41.0ma x 368v (plates)= 15.0 watts.  
There is NOTHING wrong with the plate voltage you have right now.  
You don't need to drop it at all.  
It will drop to about 340-350 volts when you use the 5Y3 rectifier and then you could drop your cathode resistor about 20 to 50 less ohms too.  
I use a SS rectifier in my SoulKicker with 370v on the plates to cathode and it rips with any 6V6GT.  
Your 12A?7 tube are sitting pretty.  
You should not, however, be using a full wave bridge rectifier but a full wave rectifer.  
Did you follow the circuit board I laid out for you?  
That's a full wave rectifier on the eyelet board.  
You might want to lower the value of that 5K screen dropping resistor you kept smoking to about 2k2 and see if your screen voltage comes up a little higher.  
That will up the voltage to your preamp a little too.  
Time to play it.  
 
Bruce  
Mission Amps
 
4/29/1999 10:05 PM
Doug

Thanks. My mistake it is a fullwave as on your board, NOT a bridge, I've really got to pay attention to these little details, for they can make all of the difference!  
Gotta go to the garage now, the wife is watching TV and wont let me turn it up!  
Thanks to All!!!!!  
Doug
 

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