At first glance it sounds like a parasitic. Unwind one end of both
suppressor coils and measure the resistors. Replace if more than 15% out of
tolerance. The ZB is over 20 years old so a little PM is necessary.
While you are at it look over the bandswitch carefully as they have a habit
of arcing on the right side of the wafer closest the panel.
Carl
KM1H
----- Original Message -----
From: <kg7hf@comcast.net>
To: <amps@contesting.com>; <amps@contesting.com>
Cc: <amps-request@contesting.com>
Sent: Saturday, December 08, 2007 12:24 AM
Subject: [Amps] LK-500ZB
>
> Hello all,
>
> I'm looking at an LK-500ZB that doesn't seem quite right anymore. I've
> had the amp for about a year now and it seems to have been working great.
> Now, I'm having a problem getting 10 meters to tune. All other bands
> 160 - 15 are ok, full output and what I would call easy to tune. When I
> switch to 10 everything goes crazy. By this I mean that using the Plate
> tune causes the swr between the dummy load and the amp to go up and down
> radically. Using the load control can produce output, but no pronounced
> dip on the plate current. Both the plate current and grid current change
> violently when trying to use the plate and load tune. This only happens
> on 10m. Any ideas?
>
> Thanks,
> Paul - KG7HF
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>
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