[Amps] [ham-amplifiers] Vacuum relay question

[Aleksandar Petkovic]

With the way you describe the symptoms, I can't begin to work out what 
is happening.

When you pull the failed relay, have you ever tested it out of circuit? 
That is, powered it and measured with an ohm meter to see if the 
contacts are moving to verify if it is a coil or contact problem.

Do you have speed up circuits (high volts and series resistor) in your 
amps?

Have you smashed or cut one open to see what has failed?

I'm at a loss but I'll follow the thread with great interest.

Cheers, Alek VK6APK.

On 5/11/2025 7:17 am, Tim Duffy K3LR wrote:
>
> A few times in the past 30 years the output relay of my single band 
> amplifiers have failed.
>
> They are used pulls – HC1 and RJ1. Typically from MGS.
>
> I am not upset that they fail – they have a finite life, but my 
> question is – how they fail.
>
> RF output goes to zero – and the meters (plate and grid) continue to 
> look normal. That is just strange to me.
>
> When the output relay fails – why doesn’t the amplifier go nuts – 
> drawing excessive current, etc.?
>
> I always have 25 mS of TX delay – so the RF is never “hot switched”.
>
> 73
>
> Tim K3LR
>
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