Hi, Don,
I think that Bands 3 and 4 are easily understood as they use L5 and L4,
respectively.
Note that switch S1B (front) connects the output of tube V1 to the
primary of L5 for Band 2, just as for Band 3, but with R6 in series.
The B terminal of L6 is then placed by S1B (rear) between the junction
of C62 and R35, with the A terminal of L6 grounded, so it places a
parallel tuned circuit across the path from V1's plate circuit to V2's
grid circuit.
But I'm looking at the schematic for the S-40B and the S-85 doesn't have
C62, so there is something going on here that I am not seeing. In
addition, C62 has a very high reactance at the frequencies of Bands 1
and 2, so I suspect that it doesn't constitute the principal coupling
path between stages.
I'll look a bit more.
73,
Maynard
W6PAP
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On 2/12/25 10:17, don Root wrote:
Maynard, I think we agree on the RF tank situation, but you have not yet
explained the V1-V2 signal path for band 1, 2.
Until we can do that, it is hard to discuss what might be the problem in
Emanuele¡¯s radio.
Richard has not yet managed to redraw any of the circuit, so I have no
idea what he has in mind.
R65 won¡¯t bother the signal path, but it might widen the tuning, and
perhaps help to decouple resonances from some antennas; who knows, but
it is a fine detail IMO.
Since Nick mentioned the L6 area operation, I have been unable to find
any answer to the signal path there, and have not seen a proposal.,,, yet.
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Maynard Wright via
groups.io
*Sent:* Wednesday, February 12, 2025 6:36 AM
*To:* [email protected]
*Subject:* Re: [HallicraftersRadios] S-85 refurbish: I've got a problem
during the RF alignment of bands 1 and 2 - trimcaps don't peak!
It certainly looks as if there is a problem with the schematic, and I
thought that was the case, but I think now that the original schematic
is correct and that rewiring it to make it look "normal" will impair or
fail Bands 1 and 2.
My thoughts about the input circuit follow. This assumes that the
signal path is coupled between the two windings of L3 even though the
Hallicrafters schematics of the S-85 and S-40B don't show that. The
very good schematic of the S-40B by dexterdxer@... does show a
dashed line around the two windings of L3, which is, I think, a good
addition to the original schematic:
Band 4:
The signal passes through L1, with D/C as the the primary and B/A as the
secondary. As the primary is connected to antenna terminals A1 and A2,
the input may be either balanced or, by using the link between A2 and G,
unbalanced.
Band 3:
The signal passes through L2, with C/D as the the primary and A/B as the
secondary. As the primary is connected to antenna terminals A1 and A2,
the input may be either balanced or, by using the link between A2 and G,
unbalanced.
Band 2:
The signal passes through L3, with D/C as the primary and B/A as the
secondary. As the signal is passed from antenna terminal A1 through the
primary of L3 (terminal D) to ground (terminal C), antenna terminal A2
is left unused and only the unbalanced option is available. Switch S1A
leaves R65 open in this position.
Band 1:
The signal passes through L3, with B/A as the primary and D/C as the
secondary. As the signal is passed from antenna terminal A1 through the
primary of L3 (terminal B) to ground (terminal A), antenna terminal A2
is left unused and only the unbalanced option is available. Switch S1A
places R65 in series with input terminal B in this position.
Condensation of this scheme:
Band 4: L1 D/C primary B/A secondary
Band 3: L2 C/D primary A/B secondary
Band 2: L3 D/C primary B/A secondary
Band 1: L3 B/A primary D/C secondary
The circuitry between V1 and V2 is also a bit odd, but I think it is
also ok as in the schematic. But it uses an entirely different scheme
than does the input circuitry.
73,
Maynard
W6PAP
--
don??? va3drl
