"Winston F. Jones" wrote:
>
> I recently bought (as-is) an old Dentron Clipperton-L amp, early model
> (serial #0906) without tuned inputs. The person I bought it from said it has
> been sitting on a shelf for several years unused. He said when last tried,
> it put out about 600-700 watts, using the three 572B tubes which are in it.
> (The fourth tube had a bad filament and he removed it.)
>
> After I received the amp, I hooked it up. Everything lights up. The panel
> voltage meter reads correct volts-- about 1,800 in CW position and 2,700 in
> SSB. When I flip switch to operate and activate my exciter, the relay clicks
> and the red light comes on,
At this point what is the plate current reading? That is with the
exciter / amp keyed, but with no output from the exciter.
>but very little RF comes out of the amp, no
> matter how I tune it. My watt meter shows about half what the exciter is
> sending barefoot. The Clipperton current meter shows only about 50 mills of
> current. I would expect the current to be 400-500 mills, even with just
> three tubes. On SSB, the amp meter does bounce a little with modulation, but
> the power is less than barefoot strength.
>
> I checked all connections inside the amp. Nothing smelled burned. Using an
> ohmmeter, the B-plus line seems O.K. from the power supply to the plate caps
> of the 572B tubes. I didn't check voltage with amp running. I'm too big a
> coward for that and I don't trust my voltmeter lead insulation.
>
> The amp seems to be biased off or the signal doesn't seem to reach the
> cathodes.
>
> My questions:
> 1. Could the tubes just be bad or shouldn't even bad tubes show more
> current?
> 2. Could the .01 caps feeding the input signal be bad?
> 3. My instruction book refers to a matching network in the parts list, but
> the input in my amp goes directly through .01 caps to the filaments.
> 4. What is the purpose of the 9.1 volt, 50-watt zener and could it be the
> problem?
> 5. What should I check next?
>
> Any help will be g reatly appreciated.
>
> 73, Winston K4CWQ
>
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