I have found SSRs to be ultimately reliable, particularly in the presence of
strong 100KW FM and 50KW AM broadcast field intensities where I had
installed countless SSRs as a solid-state relay replacement for the purpose
of controlling studio "On-Air" end-of-music, and other studio indicator
lights.
-Paul, W9AC
----- Original Message -----
From: Larry Molitor <w7iuv@nis4u.com>
To: <nospam4me@juno.com>; <amps@contesting.com>
Sent: Sunday, June 25, 2000 1:58 PM
Subject: Re: [AMPS] ssr's in qro amps
>
> 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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