On Tue, 9 Mar 1999 09:02:24 -0000 Peter Chadwick
<Peter_Chadwick@mitel.com> writes:
>
>Rich says:
>
>>? Many models of Henry amplifiers do not use a peak
>discharge-current
>>limiting glitch resistor is series with the hv positive lead. Most
>of
>>the hv transformer failures I have heard of in Henry amplifiers were
>
>>associated with a noisy arc in the RF output compartment. .
>
>Rich, what was the failure mode? Open circuit, shorted turns, or
>insulation
>breakdown?
>
>My only experience with HV xfmr failure has been insulation breakdown.
>That
>was using an (unpotted!) 1200 - 0 - 1200 in a FW bridge, in a remote
>controlled amp out in the garage.
>
>Should have known better - 1) xfmr not intended for that many volts
>from
>winding to frame. 2) using an unpotted xfmr in a damp location.
>
>It was a risk that didn't work out. However, it leads me to concur
>with Rich
>about the desirability of potting - unless you can get a mil grade
>hermetically sealed oil filled job (that isn't leaking!)
>
>73
Peter, do you mean completely potting in tar as was done ages ago?
I have not had or noticed problems with open frame xfmrs that are vacuum
sealed/impregnated.
The failures I see are the SB-220 and NCL-2000 potted types that fail
from heat when pushed by contesters.
Have not heard of any open frame failures as used by DX-peditions
either.The still popular MLA-2500 is one example.
On another thread, is there any particular advantage to the buck-boost
primary tap selection as now championed by Ameritron?
73 Carl KM1H
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