At 10:37 AM 6/24/00 -0700, nospam4me@juno.com wrote:
> I'd be curious to read
>(hear) comments from builder - users of ssr's applied
>to rf amplifier and related subject HV supplies here on
>amps. Have some of you sourced a reliable ssr that
>functions well in amp HV supplies.? Any special "hints
>or kinks" you've run into. I'd like to revisit ssr's in my
>next box should their hv ps application be viewed as
>"trustworthy."
>
>thanks
>skipp
Skipp,
I have shared your concern for many years, but the results of a recent
project have altered that opinion somewhat.
In this ham shack I have a rule: There will be NO high voltage present
anywhere during receive mode. Period. Non-negotiable. End of discussion.
This is relatively easy to achieve with choke input high voltage supplies,
but normally precludes the use of cap input filters. In order to use a cap
filter in the latest supply (for the YC156), I had to get creative to limit
inrush current and still ramp up in a reasonable period of time.
The final circuit consists of a double pole mercury relay in the 220 mains
line with two 5 ohm 50 watt resistors in series with one side of the 220.
The first resistor has a SSR (45 amp, zero crossing) across it with a time
delay of approximately 50 mS. (about three line cycles) The second resistor
has a duplicate SSR with time delay of 100 mS. Approximately 6 line cycles
after the "TX" line is enabled, full mains voltage is applied to the
transformer primary. The fluorescent lights in the shack dim less than when
the home air conditioning unit kicks on.
To accomplish "accelerated life testing" of this circuit, I simply tuned up
to full power, adjusted the keyer speed to 5 wpm, set the FT1000D for QSK
and started sending code. The supply has no trouble following the slow
speed code. Of course, one must compensate for the slight delay in amp
output, but it's not hard to do that. The supply has been used for several
contests and a lot of DX pile-ups with no problems other than what appeared
to be a single random diode failure.
I still don't trust the SSR's enough to eliminate the mechanical relays
entirely, but for surge control they seem to be an excellent choice.
Just my opinion. Others may vary.
73,
Larry - W7IUV
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