Move the wattmeter prior to relay.
On Wed, 5 Nov 2025, 12:31 pm Tim Duffy, <k3lr@k3lr.com> wrote:
> But how can it dissipate 1500 watts - when the amp output never makes it
> to the wattmeter?
>
> 73
> Tim K3LR
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Adrian
> Fewster
> Sent: Tuesday, November 4, 2025 8:31 PM
> To: ham-amplifiers@groups.io
> Cc: amps@contesting.com
> Subject: Re: [Amps] [ham-amplifiers] Vacuum relay question
>
> Probably a resistive short similar to usual load.
>
> 73
>
> vk4tux
>
> On Wed, 5 Nov 2025, 9:54 am Alek Petkovic via groups.io, <vk6apk=
> bigpond.com@groups.io> wrote:
>
> > 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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