>
>I would like to thank all of the people who answered my original post
>specially Richard Measures and Tom Rouch.
>The information presented was enlightening and informative albeit a bit
>confusing at times.
>
>The reason why I say enlightening is because in my field of electrical
>engineering that includes the design of commercial power systems, lighting,
>traffic signal instrumentation etc., the engineering principals are cut and
>dried and there is no interpretation of basic applied engineering principals
>such as voltage drop and system fault analysis. In the field of RF Power
>Engineering it appears, however that their is great deal of room for
>interpretation.
The main rub with RF amplifiers is that what is happening is way more
complex than they appear. Murphy was right.
>
>Both Richard Measures and Tom Rouch are very intelligent, highly skilled and
>respected engineers within the RF Power Engineering community.
I am not a graduate engineer. I had three years of college before I was
booted out for low grades. I got better grades in English than in Math.
>
>They have both contributed many publications advancing the knowledge base in
this
>field and have both contributed to the "design" and "development" of
>products at the commercial level. Having said that however, it is
>disturbing that their various 'egos' interfere with the presentation of
>their information.
We should be able to see past puerile feculence.
>
>Here is a basic summary of what I should do to improved the performance of
>my SB-220 based on information posted in this group.
>
>1. Replace the existing bias diodes with diodes having a 3A rating.
1a. disconnect the 110v ps from the bias contacts on the T/R relay. If
this is not done and a tube shorts, the unfused filament transformer will
melt down in short order. The same thing applies to the TL-922.
>2. Increase the L in the existing parasitic suppressors.
>3. Add current limiting protection in the form of a ten ohm RCD 175P series
>HV pulse rated resistor.
>3. Replace the existing 3-500Z tubes with new tubes
I disagree. Replacing tubes with no demonstrable problem is money in the
crapper.
>(I would assume that you
>would recommend getting good quality Amperex 3-500ZG instead of the generic
>Chinese variety?).
>
One of the tubes in my 220 is an Amperex that was made in 1967.
>Although "tube replacement" was a gray area in discussion, it would probably
>be a good idea as they have an unknown history.
>
Evaluating a 3-500Z requires a high pot. tester to measure anode/grid
leakage @8kV and grid/filament withstanding potential. 10uA of leakage
with graphite cooler tubes seems to be ok. Metal cooler tubes typically
have less leakage. // If the grid/fil. withstanding potential is under
5kV, the tube may short when hot.
>
>
cheers, John
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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