SV: [AMPS] ssr's in qro amps

[sm5ki]

The SSR:s are used in consumer electronics to among other things turn
television sets and stereos on/off by remote control. And there have been
accidents after the gear was turned off. Fire broke out at night and caused
loss of lifes. I myself disconnect all cables from my computer whenever
leaving the shack or going to bed in summertime because of a sudden
thunderstorm that may turn up. Not neccesary a direct hit may short the SSR
and cause a lot of trouble. Fire  and loss off information. Better to be
sure. 

I hope SSR in this discussion means Solid State Relay?

73s de Hans


>Från: Radio WC6W <wc6w@juno.com>
>Till: Peter_Chadwick@mitel.com, amps@contesting.com
>Ämne: Re: [AMPS] ssr's in qro amps
>Datum: tis 27 jun 2000 15.59
>

>
>On Tue, 27 Jun 2000 07:38:01 +0100 Peter Chadwick
><Peter_Chadwick@mitel.com> writes:
>>
>>I've asked before on this topic without an answer - maybe lucky this
>time.
>>What's the failure mode for SSRs? Do they fail short circuit or open?
>
>Hi Peter
>
>   They generally fail shorted... if they open, it is because they are
>broken!  :-)
>
>    I understand a stuck relay but, I dislike melted sand.
>
>    I've shied away from using them myself for the HV control...even
>though I have a drawer full of big ones, yet, I seemingly have no
>compuctions against using them for low power control: fans, heaters, grid
>supplies. etc.  
>
>
>>Working on the basis that 'Murphy rules - OK?', I've always assumed that
>the
>>failure mode is short circuit, and then figured that mechanical relays
>can at
>>least be seen to be stuck closed (well, sometimes) and gone for those.
>Plus a
>>neon indicator across the bottom electrolytic of the HV stack, a circuit
>breaker
>>on the AC feed so the amp can be totally isolated, and final line of
>defence, a
>>shorting stick. Even so, I never feel happy about touching the HV lines
>after
>>all that....but if the SSR fails short, it could be inconvenient at
>best.
>
>  I vaguely recall an interesting safety feature (not sure if it was from
>a Ham publication or one of the electronic trade magazines) that used a
>(sonic) beeper to warn if there was HV present in the abscence of the
>acutating signal.  This could be used with either an SSR or a
>conventional relay.  I'll have to dig through the files and see if I can
>find it -- though, I think it used a FET driven from the control signal
>(with a short RC delay to preclude nuisance beeping during a "normal"
>shutdown) to short the beeper which was driven from the HV (low end of
>the bleed?).
>
>73,
>  Marv  WC6W  
>
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>*
>
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