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Old 25th Nov 2013, 6:40 pm   #997
mole42uk
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Join Date: Aug 2010
Location: Bristol, UK
Posts: 1,909
Default Re: The "Sussex" Homebrew Valve Tester.

A patch bay sounds like a good idea - if you could make it conform to the AVO switch numbering somehow it would save having to re-write their valve characteristic tables.

The use of ferrites is discussed along with grid stoppers and wiring loops somewhere in the 1000 posts - and likened to the AVO practise on their testers. It isn't so much RF that you have to worry about as local oscillation generated by feeding the VUT with a 100mV sine wave on the grid and the optimum conditions on the rest of the elements to make the valve self-oscillate at various harmonics of the original. The ferrets and other tricks stop this happening. (why does my spell-checker insist on calling those little grey beads 'ferrets'?)

Richard
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