A single band problem suggests a problem in the tank. I would re-inspect
the bandswitch with an inspection mirror and a flashlight, There could
be a vapourized contact. If there is, Murphy's law says it's the contact
that is the most difficult to inspect.
>
>
>
>I have a Yeasu 2100B amp that has a problem on 40 meters. The
>load control is at the end of the range on 40 and I am experiencing
>lower output than the other bands with the same drive and plate current.
>The amp is new to me and I expect the lower loading is related to
>using Svetlana 572Bs. These tubes are fairly new and came with the amp.
>However, 80,20,15,10 react as I would expect as to output and plate
>current. All voltages are fine and the mod to increase cutoff voltage
>for the
>Svetlana has been done. The band switches look fine and the plate tuning
>is correct and in the ranges you would expect as per Yeasu. In all other
>aspects the amp works fine. I have had a parasitic event recently that
>resulted in burned resistors and a shorted grid bypass cap. The load
>issue predated the EVENT. Anyone seen anything like this related to
>Svetlana tubes or the 2100B???
>
>Larry
>WB9YAJ
>
>
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>
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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