Jim, The fact that you had the TPA parameter set to 11 degrees would explain the fan not coming on even with high heat sink temperatures - the firmware did not know just how hot the heat sink actually was because it was not properly calibrated.
The temperature displayed in the TPA setting should always be the current temperature of the heat sink. The manual instructions indicating that it should be set to the ambient temperature is correct - provided that the heat sink has had enough time to aclimate to the surrounding temperature. If you need more proof of that, set the TPA parameter as described in the manual (after the KPA100 has been powered off for about 2 hours), and then transmit for a while. Afterwards, check the TPA parameter - it will have gone up to the temperature of the heat sink. IMHO, what the manual fails to make clear enough is the fact that the heat sink should be allowed to reach the temperature of the ambient air before you set the TPA parameter to the temperature of the ambient air. There is a temperature probe on the KPA100 - it is Q3 which is in contact with the heat sink. The firmware does the calculation of when to activate the fan based on your initial setting of the TPA parameter and the current temperature of the heat sink. I am not certain just what the trip point temperatures are - one could easily check by observing the TPA value at the time the fan turns on. It would be a good idea to check the TPA setting before using the KPA100 in high temperature environments. 73, Don W3FPR > -----Original Message----- > > Yesterday I participated with my K2/100 in the Pike Special Event station > here in Colorado Springs, Colorado. It was in observance of > Zebulon Pike's > bicentennial discovery of Pikes Peak. We were in a terrible > location in a > downtown valley with antenna restrictions imposed by the city Parks and > Recreation department as the trees are older than the bicentennial. > Propagation on 20 meters was very bad from our perspective. > > Now to my point. We were outside in 90 degree plus temps for over four > hours. We were running PSK31 and SSB. PSK was kept below 25 watts. The > fan on the KPA100 did not come on the entire time. I had it set > for LoHi in > the KPA100 menu. So it should have at least been on low speed > all the time. > The heat sink got very hot....almost too hot to touch. A couple time I > though I smelled hot electronics. The PA HOT message never appeared. > > To add complications when I got home it worked as advertised in my cool > basement. I did find the temperature calibration was set at 11 degrees > centigrade (51 degrees f). Must have set it during the winter when the > basement gets chilly. I reset it to 23 degrees centigrade. (71 > f). Does > anyone know of any mystery problems or other legacy fan problems with the > KPA100? In a couple weeks I plan to disassemble it and have a > look after I > finish another K2 for an acquantance. The schematic nor circuit > description > does not address the fan itself as I can find. There is a "T > sense" circuit > but how the fan ties in is not shown as I can find. > > Your comments and thoughts will be very welcomed. > > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
