It would be difficult to rewire the S-40B to allow balanced input on
Bands 1 and 2. The S-40A uses transformers with primary and secondary
windings and resonance of the secondaries on all four bands. The S-40B
does that same thing for Bands 3 and 4 but connects antenna terminal A1
directly to the "hot" end of each resonant coil for Bands 1 and 2, with
a series 1000 ohm resistor between A1 and the coil for Band 1. So there
are no primary windings for Bands 1 and 2.
If someone really wants a balanced input below 5.3 MHz with an S-40B or
S-85, it might be useful to wind a 1:1 input transformer to place
between the receiver and the transmission line.
73,
Maynard
W6PAP
toggle quoted message
Show quoted text
On 2/10/25 10:13, Maynard Wright via groups.io wrote: Well! The email system seems to have stripped the tabs out of my chart,
but I hope it's readable.
73,
Maynard
W6PAP
On 2/10/25 09:34, Maynard Wright via groups.io wrote:
Hi, Don,
I measured my S-40B's antenna terminals with an old analog VOM, so don't
take the measurements to be exceedingly precise, but I think that they
do tell the story:
Band A1-A2 A1-G A2-G
1 540-1680 kHz OPEN 1200 ohms OPEN
2 1680 kHz - 5.4 MHz OPEN 4 ohms OPEN
3 5.3 - 15.5 MHz 0.4 ohms OPEN OPEN
4 15.5 - 44 MHz 0.5 ohms OPEN OPEN
I conclude from this:
1. My S-40B (top of chassis stamped "AUG 3 1953"; back of chassis
stamped "70E937") does not have the input coils reversed as shown in the
schematic diagram;
2. My S-40B does feature the curious input wiring that would make a
balanced line input useless on bands 1 and 2.
Added to this, my S-40B is quite sensitive and usable on Bands 1 and 2.
I use it for CW QSOs on 80 meters (and 40 on Band 3). I have always
used it with the A2-G link in place and with an unbalanced input, so I
haven't previously noticed the curious input wiring.
73,
Maynard
W6PAP
On 2/10/25 05:43, Maynard Wright via groups.io wrote:
Hi, Don,
I did check the S-40A schematic and it shows all the input coils wired
so that on all bands they can function as balanced input circuits unlike
the S-40B and S-85 that leave terminal A2 open on Bands 1 and 2.
Now, is the receiver really wired that way or is the schematic wrong?
Later today (or tomorrow) I'll turn my S-40B around and measure terminal
A2 (DC continuity to A1 and G) with the bandswitch in all 4 positions.
73,
Maynard
W6PAP
On 2/9/25 23:57, don Root wrote:
Maynard
<>
<
<>
<
<>
<>
<>
<
<>
<
<>
<
<>
<>
<>
I did not get that far. My coils between the hears are smoked now, How
it works or doesn’t gets more mysterious by the hour.
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Maynard Wright
via
groups.io
*Sent:* Monday, February 10, 2025 12:04 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!
Hi, Don,
Oops! I lost track of who was doing what here.
I have only your diagram, not the S-85 manual, but note that when the
bandswitch is set to Band 1 or Band 2, antenna terminal A2 is not
connected to anything that provides continuity except for some possible
stray coupling. The manual for my S-40B shows the same circuit but with
Bands 1 and 2 as they should be.
The alignment instructions for the S-40B specify connection of A2 to G
using the supplied link, so they are ok. The operating instruction,
though, specify removal of the link when a doublet antenna with a
balanced feedline is used without pointing out that this would lead to a
connection of one side of the transmission line to A1 and the other
side, connected to A2, open.
If the S-85 manual is similar, it might be important to take into
account the disconnect of terminal A2 on Bands 1 and 2, depending on how
you are using the receiver or feeding it signals for adjustment.
73,
Maynard
W6PAP
On 2/9/25 13:46, don Root wrote:
Emanuele, no need to reply to this, it is more for others that have an
S-85. I don’t blame you for being fed-up with this radio, and giving up;
we all have had that feeling, ?but for the benefit of others we wonder
if ?yours is wired as per the schematic, or is it actually wired like I
suggested it should be. You seem to be very good at tackling all this
stuff, so if the wiring is apparently wrong at R65, you no doubt changed
it and tried it again, I would think but I saw no comment on that point.
I don’t have an S-85, but, for any others with an S-85: does it have the
same alignment problem?, and poor sensitivity below 1Mc? ….and is it
wired as per the schematic? as I highlighted before? ?I don’t believe
they BUILD them using a schematic, instead they use a more practical
physical wiring drawing; so it is hard to believe that they went out the
door wired, and working incorrectly, but I have seen worse cases when I
was in industrial electronics manufacturing, so impossible things do
happen, then I had to find and fix the impossible out in the field. The
big boss says “ship it anyhow”, and QA succumbs.
Emanuele mentioned the S-99 is an exact copy in *some detailed
respects*, so I looked and found that the S-99 eliminates all capacitors
for the 1^st RF tanks and the slugs for bands 3,4.? ?It is interesting
that? they still list C3 with L3, but C3 itself has vanished..
???typical copy and paste draughting [drafting if you’re in USA]
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Emanuele Girlando
via groups.io
*Sent:* Sunday, February 9, 2025 12:56 PM
*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!
Guys,
one of the reasons I wants to give up with this one is the poor design
in the ANT RF circuitry.
I noticed the schematic diagram anomalies, both the 1&2 bands wiring
error and the fancy S1A-REAR layout, at the same time as Don did. I was
shocked and disappointed by that.
Days ago, while approaching the refurbishing project of my S-85, I did
read that the SX-99 is a S-85 plus IF-XTAL and S-Meter. So I download
the SX-99 schematic diagram to compare with but I discovered:
1.the 1&2 bands wiring error and the fancy S1A-REAR layout are? exactly
the same in SX-99 as in S-85; that was shocking and disappointing for
the second time (!!).
2.the ANT RF circuitry design has been completely reviewed in SX-99
eliminating TRIMCAPs and introducing a more useful antenna trimmer you
can adjust while switching between? bands and/or connecting different
antenna types input socket.
My conclusion was that the S-85 ANT circuit doesn't worth any additional
effort to be understood or further analyzed: The Hallicrafters it self
changed its design in successive projects..
Furthermore, IMHO, there is no point in having a ANT tuned circuit
inside the radio when, in everyday use, you would have to retune it
every time you change bands or the type of antenna connected to the
radio. Consequently? I got the conclusion that leaving it as "wide" as
possible sounds like a good choice.
In the hope of modifying my S-85 by reproducing the solution found in
the SX-99, I also checked if the coils part numbers were the same but,
unfortunately, they are not.
The only remaining test I want to do on this one is to align ANT and MIX
RF stages with the chassis inside the cabinet.
In other words I want to check if the service manual statement:
should be read as: "RF alignment *_MUST_* be made with chassis in the
cabinet. ...".
Thank you all once again.
--
Emanuele (IU1KNR).
<>
< <>
< <>
<> <>
< <>
< <>
< <>
<> <>
< <>
< <>
< <>
<> <>
< <>
<> <>
<> <>
<> <>
--
don??? va3drl
|
