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Wednesday, August 16, 2023

This was the culprit

 In my Astron RS-35A power supply. The symptom? Fuse blows as soon as you hit the power switch.


The culprit is one on the two main S40A1 diodes. Right now the one I removed is nothing but a fancy piece of wire. When you test it with a VOM, you get a reading of a direct short in both directions. Fortunately the other one is okay.

I'm going to order more than one, probably three. Not only is it good to have spares, but if I purchase just the one, the shipping costs are almost equal to the price of the diode! The version I took out of the power supply was rated for 800 Volts - the version I was able to find online is rated for 1200 Volts, so I should be fine, just fine.

Last time I had the same symptom in my 15 Amp supply, it was that one of the pass transistors had failed and shorted. I actually checked those first in the 35 Amp supply, but they all tested fine. I have an ample supply of those on hand should the need ever arise to replace one of those again.

By the way, if you have an Astron power supply that is broken and needs troubleshooting, and you're a neophyte to electronics repairs and have no idea where to start, may I recommend these two documents?



I left Sinar Bron 16 years ago this past April after a 22 year stint there. That was the last time I did electronics troubleshooting on a daily basis. This was a rather simple job, as linear power supplies are not that exotic. It was nice to see that I still have some of that ol' touch, and that the skills, instincts and thought processes are still there. Office work tends not to be as "stimulating", shall we say? I mean there's a bunch of problem solving and mental agility required, but it's not like knowing how to read a schematic and getting your hands dirty, and knowing in the back of your mind that you're dealing with some extremely high, and even lethal voltages. That requires a certain edge.

72 de Larry W2LJ
QRP - When you care to send the very least!
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1 comment:

  1. Anonymous7:48 AM

    Good morning Larry, very good that you were able to dust off the gray matter and dive back into hands on trouble shooting. I have an Astron RS-20 and had to replace the bridge rectifier a few years ago. The links you provided I had used the repeater builder link that was very helpful. With regards to ordering parts I too order more. I ordered the rectifier and replaced the two transistors as well. From my reading the overloading I was doing to my Astron ( running my Icom 7610 at full power) it added extra stress to the transistors. So I figured while I was there why not.
    73,
    Mike
    VE9KK

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