On 11/21/2010 6:20 PM, Richards wrote:
Gentlemen -
1) How I know if RF from my Omni VII was causing problems with my
Astron RS-35M linear type power supply ? Would it show up as an
anomalous readout on one or both meters?
Probably as a voltage change, on the internal meter or an external
meter. But the time constant may to so short it won't show on a meter.
What if I had the model
without any meters - how would one tell ?
2) Could RF be getting into it from other gear not even powered by it -
say, by a 2 meter mobile used in the shack as a base rig for local
repeater work?
Yes.
3) How could one tell if a "current" (pun intended) Model RX-35M is
grounded as described ? Is there an easy to identify spot on the power
supply's schematic diagram ? (I am a rookie at this, but might be able
to trace it with some local assistance or description here...) Or would
one just contact Astron and ask ? (...which is easy enough, but I am
trying to learn to use what info is already at hand...)
With a voltmeter in hand, unhook your loads. Apply line power and turn
the supply on. If you find voltage between the negative output and the
case, its not grounded. You could hook any 12 volt lamp between positive
output and case to make that voltage really appear between the floating
negative and the case.
I'm not a great fan of Astron supplies because in my opinion they used
too small a value for the emitter resistors that are supposed to force
current sharing and so the gaggle of pass transistors don't share well
and progressively fry. When the last one burns open, then you need a
whole set, and sometimes the heatsink compound for the pass transistors
isn't applied correctly. They have used a venerable first generation
voltage regulator IC chip for a long time that doesn't protect the pass
transistors from excess heat that the last two decades of three terminal
voltage regulators have included.
73, Jerry, K0CQ
Thanks in advance.
========================= James -- K8JHR ========================
On 11/21/2010 4:47 PM, Mike Hyder -N4NT- wrote:
The 35 amp linear Astron supplies used a floating output....
the Astron supply is good but if the negative
output post is not grounded to the cabinet/chassis then RF
energy gets into the regulator circuitry...
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