[Elecraft] KPA-1500 Fan Noise - YouTube ?

[Gmail - George]

One other thought to keep in mind - solid state amps need a lower delta T 
than tube amps. Tubes like to run hot - solid state devices not so much.

I've seen a tube with the fins so hot that the solder was in globs, while 
the transmitter was still operating. I doubt any solid state final would 
have survived that heat.

When we installed our solid state TV transmitter, it was a new learning 
curve in cooling. Both transmitters were 30 kW class AB1. The tube 
transmitter moved air faster through 3 tubes but had almost 3 times the 
temperature rise than the specs for the solid state transmitter. Our HVAC 
company and architect worked on several complex systems with air mixers 
until we just decided to use wall mounted air conditioners into the room 
behind the transmitter racks and exhausted to the front of the transmitters.

Our solid state transmitter did meet the OSHA limit for 8 hours exposure to 
noise but just barely. It was very noisy compared to the tube unit.

No tube transmitter I have ever used had a temperature shut down on any of 
the tube stages.

73 George AI4VZ



-----Original Message----- 
From: Don Wilhelm

Only one bit of correction.  If the output power is 1500 watts and the
efficiency is 50%, that 1500 watts is only half the total power
consumed, so there is 1500 watts of power that must be exhausted as heat.