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Old 14th Nov 2021, 6:45 pm   #4
turretslug's Avatar
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,328
Default Re: BC-348-Q. Receiver.

Could someone doing the overhaul have meant to fit a 68k, but picked up a 680k instead, maybe one with an orangey yellow band as it were? 68k would seem to be more in the ball-park for this application, but once fitted, the radio may have registered "within spec" with the 680k. A reflection of the way valves will shuffle their operating point a bit and carry on even with resistors a long way off spec. perhaps, and of the gain available with two RF stages.

Triode-connection does seem curious, perhaps it is a poorly-drawn or reproduced diagram. The Scott RCH has a 6K7 RF stage with anode and suppressor grid (yes, suppressor) connected together and screen grid used conventionally, maybe there was an advantage in forcing a pentode to be a tetrode, though it seems retrograde!
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