I’d venture to guess that the answer largely depends on the quality of the
materials used in a particular amp.
That said, here’s my experience with a similar amp, 2 x GU74, based on the old
Alpha 91 platform:
During the recent CQ WW RTTY, the exhaust temp fluctuated between 47C at night
and 52C during the day when the shack temp was 27C. Mostly running rather than
S&P. The fan was running at the lowest speed and barely audible.
Rudy N2WQ
Sent using a tiny keyboard. Please excuse brevity, typos, or inappropriate
autocorrect.
> On Oct 7, 2017, at 10:58 AM, Courtney Judd <k4wi@k4wi.net> wrote:
>
> I am looking for any ideas or your thoughts on what would be the safe or
> maximum operating temperature of a HF amplifier in rtty operation. My setup
> here is a FT5000 driving an Alpha 86 to about 1200 watts on rtty.... it will
> do considerably more on cw/ssb and rtty but I felt that I should limit it on
> rtty. What started all this is that after about 20 years of just sitting up
> on the shelf doing it's thing, I decided to take the 86 apart and give it's
> internals a good cleaning. Sure enough, the dust bunnies had been doing their
> thing. Gave it a good cleaning but when i went to put it back together i
> noticed that on the back panel where the air enters the amp there was a
> pre-made place to install a fan. I put a 115 v fan to push air into the amp
> which goes past the transformer then into the fan below the tubes and then
> out the top thru the tube shields. On top over the vent holes I built a
> Styrofoam box with two fans to help pull the air out. Sorta a push-me-pull
> setup. I bought a couple of digital thermometers with sensors. I placed the
> probe in the airstream coming out of the amp over the fans in the Styrofoam
> box and the other the air coming out of the 5000. This is where it got
> interesting. On rtty when running the 5000 would get up to about 103 deg F.
> from a resting temp of 79 deg. The amp would go from 90 deg up to a high of
> 155 deg which sorta made me nervous. I asked my wife if eggs would fry at 155
> and she said probably! SO, do you guys monitor your amp's temperature and
> what do you all think is save? Sorry to be so long winded but I am curious!
> thanks and 73's Cort K4WI
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