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Old 05-23-2019, 08:40 AM
dtvmcdonald's Avatar
dtvmcdonald dtvmcdonald is offline
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Impossible IF alignment instructions?

How many folks have encountered impossible IF alignment instructions?

This week I recapped my second Hallicrafters T-54. The first one was 6AU6 IF tubes, this
one was 6SH7 (metal octal). They behaved the same.

Alignment instructions say to align the IF stage by stage, last stage first,
just peaking the (single) coil at a fixed frequency. Following Rider's instructions very carefully,
this causes oscillation. No quibbles. You can't blame that on unshielded tubes with metal tubes.

Doing a sweep alignment with a magic screwdriver produced a fairly narrow bandwidth with
good shape, perfectly stable, similar to what the Rider's says it should look like ... but 1/2 MHz
lower in frequency. I never got them to align at the specified range (carrier at 26.25 MHz).
Good picture on the 7" tube.

I had a similar experience with my British Marconi 702. That set is TRF at about the same
frequency (44 MHZ) as the usual later US IF, but it had a stuck slug I had to "work around"
as an excuse.

Have other people encountered this on those or different sets? Its infuriating.
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