Chris W Tran wrote:
>
> Tuesday 30th September 1997
> Hello all
> One of our contest group - Keith Kerr GM4YXI - has just purchased
> an Ameritron AL1500x and there appears to be a problem with
> efficiency - specifically on 20m.
>
> On 80m, 40m and 15m, efficiency = 54 % approx.
> On 20m, efficiency = 42 % approx.
>
> We've followed the manufacturer's tune-up method carefully,
> and also tried numerous combinations of loading, drive level etc.,
> but cannot improve significantly on this figure of 42 %
> I think the inefficiency could be caused by :-
> Design fault - e.g. poor tank cct. design or poor plate choke
> design, etc.
> Manufacturing fault - tapping point in wrong place, etc.
> We've looked at the plate circuitry carefully and none of
> these reasons seem possible.
>
> Any ideas ?
>
> Keith is contacting Ameritron for their suggestions of course.
> Please reply to :-
> <chris.tran@zetnet.co.uk> or <k.kerr@abdn.ac.uk>
>
> Thanks - 73 Chris Tran GM3WOJ
Hi Chris,
Have you tried tuning the amp into a dummy load on 20 meters? If not
try that first to make sure the problem is in the amp. It is possible
that something is wrong perhaps from the factory construction. I have
ran into this from New Henry amps but never an Ameritron.
If the amp has a problem the next step would be to send it back or
repair it yourself. I would tune it up to max out and without moving the
cap settings, open the unit up and see where the caps are set in their
ranges. Look on the schematic and see what their values are full range
and from how much they are meshed together estimate the capacitace their
set at. You may have to make a tap adjustment but I seriously dought it.
Try what I have metioned and let me know the results.
Since you said effeciency I assume your pulling the normal plate
current or more so I dismissed that the problem is on the input.
Ron W4WA
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