Hi Larry,
What I say below is a general response to your questions, and my
personal opinion. It doesn't mean you are wrong and I am right, just
how I view the problem.
> At 09:35 AM 6/27/00 -0400, Tom Rauch wrote:
>
> >Interlocks work wonders, are easier on components, and work
> >better when working VOX or QSK.
> Tom,
>
> Are you saying that you would bet your life on an interlock?
No.
I am saying a simple interlock is more reliable than switching the
HV supply off and on hundreds of times a day or week, and
expecting something won't eventually fail, and depending on
complex external wiring to turn off HV for safety.
No matter if there is an interlock or not, I always unplug and wait. I
always check the HV meter, and then crowbar the supply.
I can't see any safety advantage when depending on a transmitter
control line to turn off the mains power to the amplifier HV supply.
As a matter of fact, I consider it a potential hazard. The operator
might be lulled into a false sense of security... depending on
station wiring and the rig being in a non-transmit mode to make the
PA "safe to touch".
Any PA that is accessible inside in a matter of moments without
disabling the mains, and any operator who reaches inside without
checking HV and crowbarring the supply are both disasters waiting
to happen. Eventually, after enough tries, it will.
> By the way, how do you troubleshoot a HV circuit? Most folks wind up
> defeating the interlock to perform maintenance and/or repairs. Have you
> figured out how to probe a circuit with all the covers in place?
Sure. I test each component, or disconnect components to isolate
problems and THEN put the cover back on to see if the fault clears.
The only exception is when I have a cover open, and then I go to a
breaker and turn the PA on while I am across the room. I
absolutely never get near the PA when HV is accessible and able
to be turned on.
I have specific covers that allow me to access non-HV areas for
certain troubleshooting, or I disable the primarys by removing the
wiring connections at some point before trouble shooting LV
circuits.
Anyone who does otherwise is a fool, in my opinion. There is
NEVER a reason to power up a PA and stick one's hands inside or
connect an external meter with HV on, except a lack of
troubleshooting skills or patience.
My life is worth more than getting a job done ten minutes faster.
/
73, Tom W8JI
w8ji@contesting.com
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