[Amps] 8877 blower requirement ?

[Peter Chadwick]

What's the mechanism whereby too much air affects the emission? Is it that the tube structure is normally well above ambient by conduction from the cathode, and excess air reduces this temperature, and, by conduction, the cathode temperature? If so, that would suggest that tubes with pins, where the thermal resistance is higher, wouldn't be so susceptible. I seem to remember back in the late 1950s, reading of some guy ( a club maybe?) in the Arctic who took cooling air from outside at -40deg C or so to cool a tx with a 4CX1000 in it without problems....

A big blower run at a lower speed, but that still delivers enough CFM at the back pressure, is quieter than a small one running faster: similarly, plain bearing motors are quieter than ones with ball bearings.
73
Peter G3RZP