While running stations on 160m at a high rate, the finals of an Omni VI got so hot that output dropped to zero. Once the finals cooled for maybe about five minutes, full output returned. We then put a small fan on the heat sink fins and experienced no further problem. No damage at all to the components. Unfortunately, the same Omni VI was hit by lightning some years later.
73, Will, wj9b CWops #1085 CWA Advisor levels II and III http://cwops.org/ -------------------------------------------- On Sat, 6/2/18, Gmail - George <[email protected]> wrote: Subject: Re: [Elecraft] KPA-1500 Fan Noise - YouTube ? To: [email protected] Date: Saturday, June 2, 2018, 6:10 AM 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. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
