[ARC5] Using BC-454 as backend

[Ian Wilson]

I am working on using a BC-454 as backend to a Morrow converter. The
Morrow produces 1525kc for a BC band car radio as backend. My plan
is to use the BC-454 with IF and BFO tuned up from its original 1415kc.
The idea is to make 100% reversible changes only.

So far I have dug out and reanimated a BC-454. This works OK as a receiver -
tested with 4MHz input. Tested all the tubes - all good except a dead 12SK7.

So the next step was to remove the RF amplifier and converter tubes and
tap into the input to the first IF transformer. This appeared to be working
OK.

Next step is to retune the BFO, align the IFTs to 1525kc (obviously I don't
know whether they will pull this far. If not, have to think of a Plan B).
However,
came across a problem - if I retune the BFO too far it apears that the IF
strip itself starts to oscillate. Not sure whether I am diagnosing this
correctly.

Perhaps a screen bypass capacitor in the IF stages? There is some sign of
leakage from some of the metal can capacitors.

Originally I left the primary of the 1st IFT floating. Bad idea. However,
putting
a few kOhm (with series 0.01u cap to keep the HT happy) to ground made no
difference whatsoever.

I'm sure numerous people over the aeons have trodden this path. Interested
in any suggestions.

73, ian K3IMW
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