It sounds like a problem on the relay board, a bad electrolytic, sticking
contacts are the most common. This is not good for the tubes so get out the
tools.
Another possibility is tube gas which is now becoming a problem if the tubes
are original late 80's Eimacs.
Carl
KM1H
----- Original Message -----
From: "Gary Hinson" <Gary@isect.com>
To: <amps@contesting.com>
Sent: Thursday, November 25, 2010 12:46 AM
Subject: [Amps] LK550 neg grid ... and bandswitch woes
> Gents,
>
> Any idea what fault would cause my old and previously faithful Amp Supply
> Co
> LK550 sometimes to register ~400mA of plate current and negative grid
> current, even with no PTT and no drive?
>
> First time it happened it took me a while to notice and, judging by the
> hot
> smell, something inside very nearly let out the smoke. After leaving it
> off
> for a few days to cool off while I mulled over what might be wrong
> (without
> any inspiration :-( ), I plucked up courage to switch it back on and it's
> working OK now, most of the time, but I've noticed the neg current thing
> again, including one time immediately after switched it on, even before
> the
> ALO trip circuit would normally let me transmit. This time it cleared
> itself.
>
> [I know I should pop the lid and look for charcoal but first I'm trying to
> comprehend what the fault would be. It's part of my 'self training in
> amateur radio'!]
>
> 73
> Gary ZL2iFB
>
> PS Any idea where I might find a new bandswitch for the old amp? I
> changed
> the padder caps recently but it still maxes-out on tune and or plate C on
> the low bands, so I strongly suspect the switch is no longer connecting
> the
> padders.
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|