[Amps] Shaded-pole Tube Blower

[Ian White, G3SEK]

Joe Isabella wrote:
>Seems reasonable to have some kind of interlock for this -- a couple 
>dollars worth of parts could easily save several hundred in new tubes. 
>A friend of mine switched to a pair of 3CPX800s because the squirrel 
>cage fan came loose from the motor shaft in his Alpha.  Tubes pretty 
>much melted.

Another experience, for what it's worth...

I once wired the blower capacitor on the 2x4CX400A 2m amp so that the 
motor ran at about half speed, and backwards. (The motor was going 
round, lots of rushing-air noises, right?)

By the time I eventually noticed there was practically no air coming out 
the exhaust, and maybe the tuning was drifting just a  little at the 1kW 
output level, the poor 4CX400As were practically black from overheating. 
But when the motor was wired correctly, they came back like new.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek