by EWBrown » Thu May 31, 2007 5:30 am
If you want to drop the 1100 ohms to (almost) 900 ohms, a nice easy "no sweat" way to do it is to connect a 4700 ohm resistor (2W or more) across each of the existing 3 X 3300 resistor array.
No desoldering needed, and it is easily reversible, if you so choose. Assuming that all the resistors are exact value (they rarely ever are) this yields 907 ohms, which is more than close enough for government work Yellow_Light_Colorz_PDT_01 Yellow_Light_Colorz_PDT_02 Yellow_Light_Colorz_PDT_04
Now all I have to do is make the wooden base for mine and it will be 100% complete! I wasn't toally goofing off lately, I managed to finally completed the Bottlehead Paramount II "enhanced iron" kits last weekend. Yellow_Light_Colorz_PDT_06
FWIW, that design uses 1100 ohms as the "cathode" resistor for the 2A3, but in a "split rail" power supply design, so that the positive B+ rail runs around 322 VDC, and the negative rail runs around -59VDC. The filament goes directly to ground through the hum balance pot.
A similar scheme is used in the 30 watt amp in the back of the RCA tube manuals.
/ed B in NH
Real Radios Glow in the Dark