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Old 12th Oct 2019, 10:01 am   #32
G6Tanuki
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Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Your "Band 6 dead" issue - can you confirm that the local oscillator is indeed oscillating on that band?

(Either use a 'scope, or - my preferred approach - use another receiver to listen for the local-oscillator; I prefer this method because sometimes the added capacitance of a scope-probe can be enough to stall a LO).

Another test-trick is to lift the grounded end of the LO grid-resistor and put a microammeter in there to measure the grid-current - this will also give you a feel for how the LO's 'perkiness' varies across the different bands/frequencies.

If the LO isn't oscillating, and 'band 6' is the highest frequency-range, first thing I'd do is swap the LO valve - a somewhat-tired valve may have enough gain at lower frequencies but not enough to sustain oscillation at the higher frequencies.
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