Wednesday, November 27, 2019

The Astron RS20-M repairs completed

Repaired and working
The repairs to the Astron RS-20M are complete and the power supply I am happy to say is back up and running. In the process of sourcing out the parts that I needed a reader of my blog gave me a glowing recommendation of Digi-Key Electronics. I am very glad that he gave me the heads up regarding this company. When I went to the site you have the option of chatting live with an agent if you have any questions. I took advantage of this several times as I wanted to make sure I was choosing the correct items. The order was placed with them and immediately I received a
Negative to case ground 
Confirmation email regarding the payment going through. Within an hour another email was sent informing me my items had been shipped along with a tracking number. My dealings with Digi-Key was outstanding, I had recently dealt with an Amateur radio store up  this way (when ordering my new Astron power supply). The only email I was sent informed me my order had been processed and that was it. I wondered if just the payment went through, if the order had been picked and or if the order had been shipped? I ended up calling them to see if it had been shipped I asked when I may expect it to arrive, so I would make sure I was home as it needed a signature. The person on the phone sounded very put out as it required them to do some digging. They did return to the phone informing me it had been shipped and should be here by Friday. When I asked for the tracking number I was told it was not store policy to give out this information?? The power supply ended up coming on Thursday, and I was not home which required me to make a trip to the post office on Friday to sign and pick it up. Let me get off my soapbox and get back to the power supply repairs.
I found this great site online regarding Astron power supply trouble shooting and repairs. This document really helped me with the trouble shooting and eventual repair of the power supply. There was another online article I came across regarding how Astron now and then has the negative terminal grounded to the case of the supply.
New bridge rectifier
The part that I had to replace was the Bridge rectifier but I also ordered some heat sink compound as this was used between the Astron case and bridge rectifier. I also removed the two pass transistors and replaced the heat sink compound there as well. As mentioned above some Astron power supplies have a wire going from the negative terminal to the case ground. I read the information (seem link above) regarding Astron sometimes grounding the negative terminal to the case of the power supply. My power supply was wired this way and I decided to remove this jumper wire, if you have the same situation with your Astron supply read the article via the provided link above and make your own decision.
With the new bridge rectifier installed and wires re-soldered, the pass transistors back in place and finally I did remove one connection of the Varistor to test it (tested ok) I had to also re-solder that back on as well. It was now time for the smoke test.......and I was pleased that no smoke was found and the power supply is now working without issue. I did connect it to the Icom 7610, adjusted the power to 50 watts and the power supply successfully passed the load test as well. This power supply is under sized for the Icom 7610, I now have a new Astron power supply that is sized correctly. I am now wondering if I should keep this supply or sell it?
Passed load test

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