On Sep 12, 2005, at 10:32 PM, Tom Rauch wrote:
> The spitting is either a bad part like a bad or burnt plate
> on a capacitor, misaligned relay contacts (the load contact
> should mechanically close slightly before the input contact)
> , or you have it loaded too lightly on 80. Sounds like it is
> loaded too lightly. Open the load control up more.
I resolved the "spitting" problem. After carefully tuning up the amp
for 80m, using as little loading C as possible to get the maximum
output, there was no spitting into the dummy load. Then I switched it
over to my doublet, which is fed through a Murch UT-2000A tuner.
Then I got the spitting, even though the tuner was tuned up for a
good match. A little detective work revealed that the spitting sound
was coming from the tuner, not the amp.
Taking the cover off the tuner revealed that there was intermittent
arcing across both the load and tune cap, favoring the load cap
first. After blowing the dust and other particles out of the case,
and off the capacitor plates -- still arcs.
It's really curious that a tuner rated for 2 kW arcs so easily at
just 600 watts of CW.
Jury is still out on the relay problem. I'll have to work on that.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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