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#1
November 4th 07, 07:08 PM
posted to rec.radio.amateur.antenna
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Power supply question
"Steve" wrote in message ups.com... On Nov 4, 11:00 am, "Jimmie D" wrote: "Stefan Wolfe" wrote in message ... "Steve" wrote in message oups.com... I pulled an old Astron power supply out of mothballs today. It's a 13.8 volt / 20 amp supply (the RS-20A). I find that there's a noticeable hum when I plug it in, and I also notice that a small output voltage of one volt or so is measureable on it even when it's turned off and unplugged. What should this tell me about the condition of this supply? As it is I'm nervous about using it. This is an old linear supply (I have one too). It could be that due to years of non-use, the electrolyte in the big filter cap dried out. The 120 cycle hum could be the current through the transformer being overloaded by foils that are shorted in the cap. In any case, you said 'mothballs' so it probably wasn't used for a long time so it might be a good idea to replace the filter cap. Buy one of similar C and V rating online or maybe you can even find something similar at radio shack. He doesnt say if its the power supply humming(normal) or if eqipment connected to it is humming. Sorry but I cant see Steve, he must have gotten on my kill file some how. Jimmie- Hide quoted text - - Show quoted text - The power supply itself is humming. It's humming fairly loudly, louder than my other Astron supply. Still, I'm less worried about that than by the lingering voltage after shut down. I know the Astron's tend to make a bit of noise. Steve It's more than likely the transformer. Try pushing down or twisting the transformer. Bolts might be loose, or too tight. You could also try mounting it with rubber washers; if you do that, you might have to add a ground lead. The reason the voltage hangs in there is that it has a bigger cap than your other supply. Tam/WB2TT |
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