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Old 8th Oct 2014, 9:29 am   #68
Phil G4SPZ
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Join Date: Apr 2005
Location: Bewdley, Worcestershire, UK.
Posts: 4,351
Default Re: Roberts RMB Problems

A strong signal at 472kHz injected at V1 grid will certainly appear at its anode and pass through the IF stage, even if the LO is stalled. This whole saga suggests that the LO has been stopping and starting intermittently throughout. Some DK9x valves can be low gain and fail to oscillate, especially if the filament voltage is marginal, as yours is. Before you do any more, hook up a 1.5 volt D cell to power the filaments at full voltage - you may find the set works.

If so, you then need to resolve the low LT problem.

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