[RFI] Astron fan circuit noise

[Ian White, G3SEK]

John Rader wrote:
>My Astron SS-30M makes noise on 80m each time the fan starts. The noise 
>starts out low in pitch and increases for about 10 seconds then stops. 
>The fan continues to run for about 30 more seconds. It is not related 
>to fan speed or duration, only starting.
>
Coincidentally, I was listening to the noise from my SS30 a few days 
ago. Generally it is very quiet, but there is a lot more noise in the 
first few seconds while the whole unit is powering-up. However, it's 
hard to imagine how the startup of a small fan could kick a 30A power 
supply into this noisier mode.

If the fan is running for such a short time, there may be a problem with 
the thermal switch that controls it. This is an industry-standard part, 
and very easy to replace.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek