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previous: frankenstein Good Man Bruce !I wish I'd talk... -- 3/17/2002 7:18 PM View Thread

Re: need more headroom

3/18/2002 8:56 PM
Bruce /Mission Amps
Re: need more headroom
"I just put a Sovtek 5Y3 in per your suggestion and am now seeing 342 v DC on the plates.... much better. Am also seeing 21.79 v DC voltage drop across the final bias resistor giving 87 mil bias. Your suggeston of a 270 ohm bias resistor would give 80 mils."
Yes, that's because you are using a choke instead of the 5K resistor in the power supply.  
Your screen voltage is almost the same as the plate voltage.  
Higher screen voltage will make the tube bias MUCH hotter.  
You could try sticking a 2K-5K resistor from your choke lead to the screen lugs.  
That will lower the screen voltage a little bit and cool your idle current a few ma.  
You still will have more screen voltage the the rest of us!  
Other then shorter power tube life, I don't see anything wrong with what you are doing if the power tube's plates are not glowing red after playing hard for a few mins.  

frankenstein Bruce: I was under the impression t... -- 3/19/2002 5:19 AM