Do FlexRadio service technicians use 'floating or grounded [negative]' output, 13.8VDC power supplies when bench testing radios ?

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Terry AB2UE

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Posted 3 weeks ago

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Steve - N5AC, Employee

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I'm not sure I understand the question, Terry.  This answer is probably going to make it sound like you don't know what's going on with DC power, but I'm not sure how else to answer (so sorry for that).  It's almost certainly me that doesn't understand!  On the DC side of the supply, you should have two connections -- ground and +13.8V.  Both must be connected.  If you are asking about whether the GND output on the supply is connected to the GND pin on the AC plug, I have no idea about the design of the supplies.  All of the supplies we have use IEC 320 C13/C14 connectors.  Also, none of the radios, themselves, are grounded beyond this on the bench when we test.  Most all of the supplies we use are switching supplies, but I'm not familiar with the electrical code requirements on AC/DC supplies to know whether there is a requirement that the AC ground pin be connected to DC ground.  Does this help?
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Terry AB2UE

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Steve, i selected ' write a reply' instead of 'comment' on your post, see my reply below, thanks, Terry AB2UE
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Ken - NM9P, Elmer

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It sounds to me that he is asking if the DC Ground is isolated from the chassis ground or the third wire AC ground. (Perhaps on both the PS and rig).
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N5LB - Lionel B

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Samlex 1235 switcher isolates the negative terminal from its chassis ground. This per the Samlex manual, though I have not verified. So when connected to the Flex the ps negative is only grounded at the Flex.

My Astron linear supplies all connect the negative to the chassis ground.

This doesn’t seem like it makes any practical difference in this application.
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Terry AB2UE

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From the factory, my Astron linear transformer DC power supply negative terminal is grounded to both the chassis & the AC power cord ground pin.  In some cases, this can cause problems with hum & or ground loops in the ham shack.  I would like Steve to test the Flex switching supplies for  continuity between the DC[-] terminal & AC power cord ground pin, to see if the DC output is grounded or floating above ground. Thanks, Terry
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Tom W3FRG

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I use a Powerwerx SPS-30DM that has the negative terminal tied to chassis ground. This was both measured and also verified by Powerwerx.
I use a Flex 6600M and have had very good and unsolicited audio reports using either the MIC or BAL microphone jacks.

Tom W3FRG
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Brad A. Steffler

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Terry,

Thanks for raising a question that never had occurred to me. I have had a hard-to-find intermittent hum on output problem on my old 6500. I have not put my new 6700 to work, because of health problems. I will have to research this if I still have a hum problem.

Thanks for the ideas.

Brad
KE4XJ