Im just getting into this H-691. Do I need to do anything special to run this without A and B type batteries. So far I changed a couple of resistors and electrolytics. I had to order 2000 ohm 10 watt resistor. Thanks Ralph
You should good to go. No batteries needed in the circuit when operating on ac. The 7.5vdc coming off of R-9 is critical. If too high it can shorten the life of the tubes filaments. Too low there won't be enough emission from the filament for the tube to operate at it's full potential. You would want to be somewhere between 7.0-7.8vdc.
GL
Thanks Terry, This is only my 3rd vintage radio for me to work on and wasn't sure about the batteries.Thanks, Ralph