Much obliged Wet_Boots. With your input I went ahead and made the small gamble of picking up the new Hunter timer. All's connected and running well. I think the valves respond (open) much more quickly to the 24 volts (28 per my multimeter) from the new Hunter timer. The buzzing from the one solenoid valve is gone, too (for now?). I am enjoying the long thread elsewhere here on the RC-7 etc. old Rainbird electro-mechanical timers. The friend whom I helped today marveled at the weight and size difference. Of course, whether the new Hunter electronic controller will last the 30 years that the RC-7A model she had is in question. Gonna maybe try to sell the old RC-7A controller on Ebay for the price of shipping.