Check that the bandswitch contacts haven't burned off.
On 11/16/2010 5:43 PM, Larry wrote:
> A number of you offered suggestions a couple of weeks ago and I checked those
> suggestions a couple of times. I have finally got back to trying to track
> down what
> is probably a silly error on my part that has broken my Clipperton-L. The
> mods were
> triggered by the destruction of the original parasitic suppressors. The amp
> was
> working - just not well in all conditions.
>
> I replaced the power supply board (just an upgrade to better supply),
> replaced the
> plate RFC to an Ameritron AL-572 RFC along with the parasitic suppressor
> board,
> changed the plate bypass cap at the power supply side of the plate RFC to a
> 0.002uf
> value, changed the plate blocking cap to 0.002uf, changed the filament RFC to
> a
> bigger unit, and changed a couple of doorknobs for 160 (unrelated to the
> original
> problem of the parasitic suppressors). I haven't gotten to 160 yet. The
> current effort
> is using 40. The current result is still no output
>
> 1. There is plate current (as measured by the panel meter) and there is plate
> voltage.
>
> 2. I don't have a HV probe but I could measure at the plate voltage (at the
> plate caps)
> as the voltage was dropping after turning off the power switch and it tracked
> with the
> panel meter.
>
> 3. The idle current seems OK.
>
> 4. The plate current follows keying. The plate current changes as it should
> as the driving
> power is increased or decreased.
>
> 5. Adjusting the output cap controls has no noticeable effect on the plate
> current (no dip
> etc).
>
> 6. Using an ohmmeter there is continuity (short) from the output network side
> of the plate
> blocking cap (on the cap lead) to the output connector. From the other side
> of the
> plate blocking cap (on the cap lead) to the power supply there is continuity
> (short).
> Thinking perhaps the new blocking cap might be bad I replaced it with a pair
> of 0.001uf
> in parallel but still have the same result. (I remeasured the shorts after
> replacing the
> blocking cap.)
>
> 7. The output relay is switching as it should. None of the wiring to the
> relay was touched
> in this mod.
>
> It has been a long time since I worked on an amp. I am sure I am overlooking
> something
> small and silly. I was hoping one of the gurus here might have a pointer or
> suggestion of
> something I might have missed.
>
> Thanks
>
> 73, Larry W6NWS
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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