Power supply failure!

Dusty but looks ok 
I got up Saturday morning with plans of getting on the air and participating in the CQ Worldwide CW contest. Well that was the plan and I did get one contact in the logbook but as I was working the second contact my power supply made a thump followed by my Icom 7610 abruptly powering down. When this happened it left me with a bad feeling and an uneasy understanding that the contest for VE9KK was done! I was hoping that for some reason the crowbar protection kicked in and I would just be able to restart the power supply and all would be well. That was not the case my Astron RS-20M was dead in the water. I checked the 5 amp inline glass fuse and it was blown catastrophically. I replaced the fuse
and turned on the power supply hoping for the best and the best did not happen, the power supply did not turn on and I found this new fuse had blown as well. One thing was for sure and that is the CW Worldwide CW contest was over. My thoughts were on the power supply and getting the cover off to see if anything was obvious as to what the issue was that I forgot about my Icom 7610. It was about an hour later it occurred to me......"did my 7610 suffer any damage?" Since my power supply was out of service I had to come up with another way to power up the 7610. I decided to use the battery that is used with my Elecraft KX3 for outdoor op's. I connected it up and pressed the 7610 power button and NOTHING happened!! I just felt sick at this time, my brand new Icom 7610 also took the hit as well? I was thinking about checking the Icom 7610 inline fuses to see if they saved my rig by taking the fault? I decided to take a break and do some thinking and I was glad I did. On my return to the radio room, I decided to check the battery voltage and low and behold it was at 10 volts and the Icom needs 12.7 volts DC to power on. I charged the battery ( that was the longest hour ever!!) and tried again and thank goodness the Icom powered on. It was now time to get back and troubleshoot the Astron power supply. It was now time to see if there was any visible damage to the internals of the power supply?
 I was not able to see anything in the power supply with a visual check. Checking the schematic diagram I checked out the power on switch and it was good, next
Bad Varistor  
was the varistor if it was shorted that would cause the fuse to blow. I found the varistor to be open, this is not good and I have to replace it but this would not cause the fuse to blow. I then disconnected the secondary transformer connections from the bridge rectifier I then replaced the inline fuse and powered up the power supply. Everything was good and this was great news as it was not an internal short in the transformer. I then connected the transformer to the bridge rectifier and powered up. The inline fuse blew as soon as the power supply was turned on. I then removed all connections to the bridge rectifier leaving the
Shorted diode 
AC transformer input only, once I powered up the Astron the inline fuse blew again. It was time to investigate the bridge rectifier and see what was up. The investigation showed a short in one of the diodes in the bridge. At this point, I am replacing a thyristor and a bridge rectifier. Next in line are 2 transistors but time was not on my side and that is going to have to wait until Monday to do.
Mike Weir, VE9KK, is a regular contributor to AmateurRadio.com and writes from New Brunswick, Canada. Contact him at [email protected].

15 Responses to “Power supply failure!”

  • n1kdo:

    That power supply is too puny for your IC-7610! You need a RS-35 for that, something that can make 20-25 amps nearly continuously. It’s not a surprise to me that the bridge failed. I use these things pretty hard in repeater service.

    Those Astron linear supplies are easy to repair, as long as the transformer works. If you need to change a pass transistor, change them all. Good luck.

  • Mike VE9KK:

    Good afternoon Jeff thanks for taking the time to comment, I have been running the rig at 50 watts but I am guessing using it for FT8 at that power or a bit more was to much. I have the proper Astron power supply on order now. I am checking the pass transistors today. So far it’s a varistor and bridge rectifier that are needed. If one is defective for sure both will be replaced.
    Thanks for stopping by and have a good week.
    73,
    Mike
    VE9KK

  • Carol Laferty K4SAF:

    Are you talking about the CW CQ DX Contest? If so, it is Nov 23 and 24. https://www.cqww.com/

  • Carol Laferty K4SAF:

    I meant to say CW CQ DX Contest….

  • Howard vk3qa:

    Hi depending on the age of the supply it may be worth replacing the electrolytic caps while you are there.

  • N4ZDU Robert:

    Well the Rectifiers are the FIRST thing I would have checked.Just be glad you even have a radio to get on the air with!, I have not been on the air for several years,no radio, I am stuck with $714 a month SS and cant buy any radios. so I am dead in the water,I cant even listen anymore.
    Have fun while it lasts.
    73
    N4ZDU

  • VE3CMQ:

    Hi. Varistors should always read open. Also, the transistors may have failed. If I am not mistaken, 2N5886’s work well in those supplies. It’s been a while since I repaired those supplies. If the transistors blow, they would usually short, giving the radio 20V or so. Most, but not all of these supplies have a crowbar circuit built in to blow the fuse if the output voltage gets too high.

    I’d replace the bridge with a 50A, 100V or larger version. Digikey is a great place to get these from. Delivery is usually 2 days or less.

    73, Clint, VE3CMQ

  • Vic, KB7GL:

    I would would also check the pass transistors…easy to remove. And, clean ALL the old dielectric grease off the transistors, insulator and the chassis and replace it with new. You should also check the tension on the pins…gently squeeze the socket pins, if necessary.

    I also agree with the comment about the RS-20…it is designed to operate continuously at considerably less than 20 Amps, which is insufficient for your needs.

    I have both an RS-20 & RS-35…the RS-20 is used only for an FM mobile transceiver base station. The RS-35 powers my K3.

    These are very good power supplies…I like them much better than the switching type. Clean it up & it should last a long time.

    73, Vic KB7GL

  • Mike ve9kk:

    Good evening Carol thanks for stopping by and enlighting me to my retirement memory……:) I would guess if my radio had not shut down I would have eventually figured it out. Thanks for the reminder and my new supply should arrive before the contest and I should be good to go.
    Thanks for stopping by Carol and have a good week.
    73,
    Mike
    VE9KK

  • Mike ve9kk:

    Top of the evening Howard the supply is not that old and I did check the cap’s and all seemed to be just fine. Thanks for your time and input have a good week Howard.
    73,
    Mike
    VE9KK

  • Mike ve9kk:

    Good evening Robert, yes I am very happy to have a rig and very very happy to have the rig I have. I am very fortunate and thankful that I am retired and have a pension from my place of employment. It does seem the rectifier is the only part that let go.
    73,
    Mike
    VE9KK

  • Mike ve9kk:

    Good evening Clint and nice to hear from an Ontarioian, I feel like such a dope and I just don’t know what I was thinking regarding the varistor in this post. Thanks for being very kind regarding my poor oversight of the varistor. This afternoon I did check the pass transistors (there are 2 of them in this supply) and they were just fine. The power supply does have crowbar protection as well. This supply is to small for the 7610 and I have on order from Radio World in Toronto the proper Astron supply and it should be here this week sometime.
    Have a great week Clint
    73,
    Mike
    VE9KK

  • Mike ve9kk:

    Good evening Vic thanks for taking the time to comment, this evening I checked the pass transistors and they passed with flying colors. It seems the bridge rectifier is the only part that has to be replaced. I do have another Astron power supply on order and it is the proper size for the 7610 to operate at full power. As for the dielectric grease, I am also ordering it and replacing it on the pass transistors as well on the new bridge rectifier.
    Have a great week Vic,
    73
    Mike
    VE9KK

  • Rich WB3EGD:

    This is a comment for Robert, N4ZDU. Robert, your e-mail addresses listed on QRZ.COM are not working. I thought I’d let you know that there is a web site that allows licensed hams to operate other participating hams’ and ham clubs’ stations remotely. You register on their site, download their software and upload a copy of your license to their site and then you ask permission of a station’s control operator to transmit. Even without permission, you can usually listen. If you don’t have a computer, you can even do it from an android smartphone. There are dozens upon dozens of remote stations on line at any given time.

    Here’s the link to the RemoteHams site.

    https://www.remotehams.com/

    I just stumbled upon this YouTube video of a ham in England using RemoteHams to make an over-the-air QSO with a ham in Spokane who coincidentally was not far from where the particular remote station is located that the ham in the UK is using.

    https://www.youtube.com/watch?v=xefrKQbK6rQ

    And, here’s a brief YouTube tutorial that popped up:

    https://www.youtube.com/watch?v=W1wlmawAP5k

    I hope this helps you get back on the air, even without a rig. Good luck to you! And, good luck to VE9KK with his amplifier troubleshooting!

    73
    Rich
    WB3EGD

  • Frank , EI7KS:

    If a power supply unit has a marginal capacity for the job in hand ,add a 60 to 100Ah battery ,via a 40A diode and between battery and transceiver a fuse
    Then you also will be able to keep operating (for some time) in the event of a power cut
    If the voltage drop over the added 40A diode is too high you can compensate by increasing the PSU output voltage (through a usual trimpot)

    An old car battery which no longer start the car smoothly will highly likely be adequate for the above task .

    Frank , EI7KS in County Wicklow -Ireland

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