I have 2 SEC1223's and no hash. I also have an Astron RS35 and RS50 linear
supplies. Sometimes the magnetic hum from them drives me crazy. The little
cork pads Astron puts in them to alleviate this
does not help much. I keep them under the closed console on the floor.
Mike WA8EBM
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <elecraft@mailman.qth.net>
Sent: Tuesday, July 08, 2008 6:28 AM
Subject: [Elecraft] Switching Supplies
Pardon me if someone has already pointed this out (I have not followed the
entire thread)- my past experience with linear supplies reveals an all too
often failure mode of either shorted pass transistors or blown control
chips (LM-723). In either case the output voltage from the supply can
rise to the unregulated DC filtered voltage (usually 20+ volts) and cook
anything attached. A fast and effective crowbar, if designed correctly,
will clamp this voltage before it destroys your expensive equipment. With
switchers my experience has been that one or more of the switching FETs or
high speed diodes fail and the supply just dies (no output). Which one
would you rather have connected to your brand new K3 if it failed?
73
Rodger
N4NRW
counting down the day till the K3 arrival!
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