[RFI] Icom Switching Power Supplies

[Dale]

Leonard,

I use an Astron SS-30M, which is very RF-quiet.  There have been reports of other switchers, notably those in the base of CFLs, creating a noise increase prior to failure.  You may very well be correct about component aging, but the actual issue could be more serious.  Do you have any means to measure the temperature of the switching device (transistor or FET) itself?  

A very key part of flyback topology switcher design is the snubber network.  Where/when used, they keep the peak voltage across the switch from exceeding the rating of the switch device.  Changes in value from either use or heating can lead to more heating (due to greater losses) or switch failure (due to lack of the snubber).  Not all switchers use the flyback topology, but many do.  A very long time ago, I had first hand experience with snubber failure in some high power (10 kW) switchers - not nice, unless you like fireworks at close range!

If you are able to get a temp sensor on or near the switch device, please be careful, as they typically have around 300 volts DC on them and they are referenced to the incoming AC power line.  Good luck, and please let us know if you find anything.  Last minute thought: if you open up the PS-25, be sure to inspect solder joints.  A poor solder connection, especially in the snubber circuit or switching circuit, will cause more heating and problems.  

73, Dale
WA9ENA         


-----Original Message-----
>From: Leonard Halvorsen <lhalvors at pppl.gov>
>Sent: Mar 21, 2014 7:29 PM
>To: rfi at contesting.com
>Subject: [RFI] Icom Switching Power Supplies
>
>*Has anyone noticed an increase in background noise in the ICOM PS-25 after
>it has had a chance to age for a while? I have one (of two) on which the
>noise has begun to creep up enough to be noticeable on 160, and is starting
>to come up on 80. I've had them for about 2 or 3 years, now. I suspect
>aging effects on components. Anyone have similar?*
>
>*wa2amw*
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