by EWBrown » Wed Nov 21, 2007 7:19 am
The simplest and easiest approach is that addressed in the previous reply. I do subscribe to the "simpler/easier is better" theory in most cases, but also like to experiment and try out some "strange" ideas from time to time. (visualize some of those old fashioned "flying machine" crack-up photos from the early 1900s) :o Yellow_Light_Colorz_PDT_09
If you still want the 6AX5 for supplying the 6SL7 by itself, proceed as follows: (it gets a little complex, but not insurmountable).
The PA-774 secondary wires (two "hot" and the CT) connect at the ten-place barrierl strip, that would be the best place to connect an extra set of leads (using spade or ring lugs) which, in turn, would go to the "external" SS rectifier circuitry, that can be mounted on one or two small terminal strips.
I'd go with two uF4007s or uF5408s, two 100-220 uF / 450 V caps, and use the choke that is already in place, just disconnect it from its two barrier strip connections, and connect it between the + end of the two added external caps.
Connect a 50 ohm (or higher value) 2W resistor to the two barrier strip locations where the choke was connected. Since the 6SL7 by iteslf draws very litle current, a larger resistor could be used, anything 100 ohms to 1K (or even higher) , the actual current consumed by the 6SL7 is around 1.2 mA total. A 1K resistor is going to offer a 1.2 VDC drop, so it is rather insignificant. The idea is to get about 150VDC "resting" voltage at the plates of the 6SL7.
HTH
/ed B in NH
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