[AMPS] ssr's in qro amps

[Tom Rauch]

> >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.
> 
> You know as well as I do that circuits can be designed to rapid cycle
> reliably. For instance, pulsed radar,

Do they turn off the main energy storage in the system? They do 
not.

>the flashing yellow light at the
> intersection down the street,

Life of the lamps is greatly shortened, but once again they do not 
turn off a supply with considerable stored energy.

>a microwave oven oscillator/PA

On 2 minutes, off half-a-day. Of course on low temperature modes 
some cycle the supply off and on, but a microwave supply is 
unfiltered or poorly filtered at very best. Because of that, there is 
little or no stored energy.

>and switch
> mode power supplies. 

Switch mode supplies have little stored energy, as a general rule. 
Even with that, most are not cycled off and on with each 
transmission. They simply haven't the response time to follow 
waveforms in most transmitters, plus it is needlessly hard on 
components. 

>I have a choke input HV supply that I have used in
> this mode for twenty years without a single failure. This new cap input
> supply is still in question, I'll get back to you in twenty years.
 
That's fine, if it works for you. I'd never do it, or design it into 
anything that had considerable energy storage or that required fast 
switching rise times. 

> As for as wiring, it is no more complex that that used to operate the
> customary vacuum relays and/or the cutoff bias for the tube. Again, I just
> don't see a reliability issue.

Depending on external wiring and external device operation as a 
reliable safety feature is foolish. 

Someone could bump the key, trip the VOX, or accidentally push 
the PTT switch. The wires could come unplugged and fault into an 
"on" mode. The relay in the exciter could freeze-up.
 
> >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.
> 
> Good advice. I never said not to do any of this. I absolutely agree.

Then the problem is solved. 
 
> >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.
> 
> We have a real problem here. Perhaps it's just semantics. I do not depend
> on this feature. It is just one of many redundant things I do to increase
> my chances of being around long enough to work another new one on 160.

That's fine. As long as you don't depend on that method for safety  
and the supply does not have reliability problems, or isn't changing 
while the transmitter is on.

As I said, it would never work for me because I use QSK or VOX, 
or semi-break-in CW.
 
> >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.
> 
> Unworkable for me. I cannot read the meters, scope, spectrum analyzer,
> etc, from across the room without binoculars. 

I can't think of a single thing that needs to be measured or tested 
that can't be measured with the cover on...or in a static safe test.

Can you give me an example of some aspect that needs to be 
tested when operating with the cover off, that can't be isolated 
some other way?

I'm at a loss Larry.
73, Tom W8JI
w8ji@contesting.com

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