Max Safe Temperature for Transmitter

marwalk

When using digital modes, such as Olivia, which are constant key-down by design, I've observed that (understandably) the transmitter temperature rises several degrees C within a very short time. This is with the power cut back to 30 watts, with not much difference when backed off further to 20 watts. (The temperature readings are from the K9DUR SDRMonitor 3rd party utility, which I've found very useful for this purpose.) I'd read that the auxiliary fan in the front of the radio comes on at 70 deg C (seems fairly high to me but I'm not sure, and I'd like to know if that is a sign to back off the power more). When I'm key-down with Olivia for over a minute the transmitter temperature climbs past 50 deg C (at 8/250 that only allows about a paragraph or even just calling CQ). At what point (and more specifically what temperature) is there risk to the transmit module?

Thanks, Mark, AC3EW