K5RC wrote:
> I use Emtron DX-4 amps in my contest station. I chose them to ensure my
> guest ops do not blow them up. They have excellent fail-safe protection.
>
> One by one, however, I am having problems with the vacuum relays. They are
> developing intermittent contact on receive. Banging on the front panel is a
> temporary cure.
>
> Emtron's remedy is that I need to run the amps at full output to have them
> operate effectively and reliably. I choose to run them at the legal limit.
>
> That notwithstanding, I understand that there are vacuum relays that are
> designed for low-current applications. Also, Emtron mounts the relays
> vertically instead of horizontally (as Alpha used to do). What is the
> experience of the group on the physics of vacuum relays?
Hi Tom,
They always seem to fail this way.
You should (probably already have?) checked for hot-switching. Make sure the
time between
the amp-out signal from the exciters and the onset of RF is long enough. I
don't know what
kind of vacuum relays they are using, but the Jennings RJ-1 / Kilovac HC-1 type
require
about 8 ms minimum if you don't use some kind of speed-up circuit.
I don't see how running more transmit power would affect the receive side.
Some people have suggested that reversing the coil leads can give them a new
lease on
life. If the problem is caused by something getting magnetized this might help.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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