Tried sending this earlier, trying again...
------
Hi Charles,
Thanks for your thoughts on this. When I bought the amp I was told
the switches and meters were replaced. The old meters did not come
with the amp but the two old push button assemblies were given to me.
Its surely possible the replacement switch has gone bad and may need
to be replaced again. Being a new switch my initial thoughts are the
relays but I'm not sure a stuck relay would do what is happening.
The amp usually runs as expected but recently I have found the off
switch to have no effect and I must unplug the amp to turn it off.
Re-connecting the plugs turns it on and it goes through the 3 minute
warm-up. Again, the off button has no effect but the rest of the
buttons on the gang do work as they should. Thinking it might be a
stuck connection, while the amp was running I pushed in the off
button & then put a dowel against one of the chassis screws in the
back to the left of the vent and gave a light tap with a hammer and
the amp instantly turned off.
It will remain working normally for some time but then the issue
returns and though I can "fix" it by tapping, that's no solution and
eventually may cause other failures so I need to resolve it
correctly. Not sure how to best visualize the relays but I suspect
removing the side panel and the transformer will let me access them.
If I need to get new relays, is there a part # for these specific
relays?
I need to know if a sticking relay would cause the amp to behave as
this one does. If not, then I will likely have to put in a
replacement switch.
73,
Gary
KA1J
> Aging Alpha amps with the push button pop-out switches are a bear
to
> find and to replace. The larger problem other than unavailable
part
> and wear failure is that with the pop-out design, u can not just
> replace one of the gang.
>
> On relay contacts and Morse keys, I start with a piece of clean
> typing/printer paper and put that between the open contacts and
then
> push them closed trapping the paper between them. Then, pull the
> paper out, wiping both upper and the lower contacts. You can do
> this a number of times until the paper remains clean afterward.
>
> That very gentle solution sometimes works. If not, then u are
into
> very very fine emery cloth from a jeweler.
>
> I suspect a sick switch but relay is also possible, as you know.
> 73
>
> Charles Harpole
> k4vud@hotmail.com
>
> > From: Gary@ka1j.com
> > To: amps@contesting.com
> > Date: Tue, 22 Oct 2013 00:17:02 -0400
> > Subject: [Amps] Alpha 77D likes to remain on
> >
> > Recently this 77D converted to SX wants to remain on regardless
of
> > the selection on the power switch. I found if I bump the back of
> the
> > chassis it resolves the problem so whatever it is, it's jarred
> loose
> > via a small tap to the chassis. I'm thinking one of the HV
relays
> has
> > some pitting on the contacts and is staying closed once engaged.
> >
> > Any alternate possibilities and if I'm right, how to best dress
> the
> > contacts so they won't stick again?
> >
> > 73,
> >
> > Gary
> > KA1J
> > _______________________________________________
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> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
>
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