Astron RS 35M humming issue

[bobruzzo]

I have an Astron RS-35M power supply I bought in 2020. It has developed a HUM over the last 8 or 10 months. Not very loud, but def audible, but only on TX. When I TX with more than 5 - 10 watts it hums, then when I unkey radio hum stops. There is no hum on my radio signal and voltage/Amperage is rock steady. I took cover off to check if maybe transformer has loose bolts. Everything tight. No symptoms other than annoying hum. I have a much older Astron RS-35A (no meters) and that power supply dead quiet. I asked around in my radio club for help and the consensus was "some power supplies hum" and there are no other symptoms. I looked inside and everything looks new. So not sure what could be causing the hum. At first I thought the cover vibrating. When I TX, I push down slightly on top of cover and hum muffles a small bit so something inside causing it to hum.

 

[jazzboypro]

I do hear hum on mine too but i really have to pay attention and be close to the power supply to hear it. My RS35M is over 20 YO so it might be normal.

 

[G7RUX]

I have an Astron RS-35M power supply I bought in 2020. It has developed a HUM over the last 8 or 10 months. Not very loud, but def audible, but only on TX. When I TX with more than 5 - 10 watts it hums, then when I unkey radio hum stops. There is no hum on my radio signal and voltage/Amperage is rock steady. I took cover off to check if maybe transformer has loose bolts. Everything tight. No symptoms other than annoying hum. I have a much older Astron RS-35A (no meters) and that power supply dead quiet. I asked around in my radio club for help and the consensus was "some power supplies hum" and there are no other symptoms. I looked inside and everything looks new. So not sure what could be causing the hum. At first I thought the cover vibrating. When I TX, I push down slightly on top of cover and hum muffles a small bit so something inside causing it to hum.

Sounds like loose transformer core laminations.

 

[AK9R]

Sounds like loose transformer core laminations.

Or, maybe just loose parts. Wouldn't hurt to take the cover off and tighten up all of the threaded fasteners. Just don't touch both terminals of the big capacitor at the same time.