[Amps] Vac relay coils in series ?

[Jim W7RY]

Ive never had a coil fail on one of these types of vacuum relays.

Had a NC contact fail on a RJ1A.

73, Jim W7RY


On 3/16/2022 12:01 PM, jim.thom jim.thom at telus.net wrote:
> I'm installing  3x vac relay's into an amplifier.  (Input, output, and cut
> off bias).  Coils are available for both 12 vdc ( 80 ohms)....and also 26.5
> vdc  ( 335 ohms).  The amp has to be able to handle a kw on bypass, since I
> series 2 or more amps...tuned up on each end of the same band, or tuned up
> on different bands.   A simple rotary switch is used to engage only one key
> line at a time.  Simple interlock.  IE: switch positions  1+3+5+7 are used
> for amplifiers  A-B-C-D.   Switch positions 2+4+6+8  are used for bypass.
>
> What is the 'normal'  failure mode for a vac relay ?   Is it the  coil that
> goes open, or does the armature inside  bind up, and then stuck ?
>
> The thought here is, IF the coils are wired in series, say 3 x 12 vdc
> coils...and if any one coil ever opened up...then none of the relay's
> would operate.
>
> Worse case scenario is if the OUTPUT relay failed to operate..... then
> drive is still applied...and NO  ant  connected  to the output of the amp.
>
> But I don't know what the ..'normal' failure mode of a vac relay is.   I'm
> talking about the HC-1,  RJ1A,  GH-1  type relays.  They all have a screw
> on the base, to swap coils.  IE: coils are field replaceable..with either a
> 12 vdc or  26.5 vdc coil.
>
> I use a delay in the TX inhibit lead on the xcvr, (to give the relays in
> the amp a head start) so the exact sequencing of the 3 x relays is a moot
> point.
>
> I have a choice of either 31 vdc or  62 vdc to power the 3 x relays.   IE:
> 31 vdc + a  19 ohm  series drop  resistor to  power  3 x 26.5 vdc coils in
> parallel.
>
>   OR   use  62 vdc + a 173 ohm series  drop resistor, to power  3 x 12 vdc
> coils in series.
>
> Tnx.... Jim   VE7RF
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