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Philco 71 E IF adjustment instability
sandbar40
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Posts: 10
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Joined: Jul 2012
City: New Zealand
#8

08-05-2012, 12:43 AM
Checked lead dress - ok - most of wiring is still original.
Re-did alignment starting with 2nd IF feeding sig. gen. at 260 khz via 0.1 cap to grid cap of '44' which peaked ok, then moved gen. to grid cap of '36'. This time adj. of either trimmer resulted in osc. while approaching peak.
This behaviour reminded me of the old regenerative sets where max. sensitivity was just before osc.
With a stable setting of these two trimmers set goes quite well, but i'm still puzzled by this behaviour.
Also i wonder why there are blanking plates covering the two IF primary trimmer access holes on the rear of the chassis, - were these settings more critical and not normally touched ?
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RE: Philco 71 E IF adjustment instability - by sandbar40 - 08-05-2012, 12:43 AM



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