[Hallicrafters] S-36A HF reciever (stuck)

[John Schmitz]

Doug,
Hey, that's my S-36A at schmitzhouse.com.

Anyway, looking at your further descriptions and some of the other guys
comments it definitely looks like you have an RBK. The different models and
versions were puzzling to me as well when I first got started on this guy.
The RBK's had the Anti-Radiation (AR) tube and the Panadapter PL-239 which
mine does not have, that's why my RF assembly doesn't like yours. Sounds
like if you can figure out where that broken wire goes you'll be in
business.

I did struggle for a long time with the RF section. Completely tore it down
and rebuilt it twice. Tuning it is a real challenge. Not sure about your RF
assy but mine had long lengths of what appeared to be excess wire off the RF
Assy coils. It turns out that that's how you can change the inductance of
the coils if you really want to get down to tuning to precision. Depending
on where you solder down on that length of excess wire changes the
inductance, so if you have what appears to be excess lengths of wire off
your coils don't cut it off.

Another thing I found was different tubes in the RF section will change
things drastically. I had ordered a set of acorn tubes from Fair Radio
Sales. Once I got the RF assy all tuned up I was still not quite happy with
the sensitivity though it wasn't bad. I ordered another set of acorns from a
different dealer and WOW what a difference those tubes made!

I can't say that Fair Radio had crappy tubes though. I did quite a bit of
work on UHF communications equipment in the Navy and one of the things I
discovered pretty fast was different tubes, due to slightly different
inter-electrode capacitance, performed differently. I soon had a whole
drawer full of tubes and I would swap tubes as part of tuning and alignment
to get best performance.

Another problem I had was getting the RF assy to track the dial. That took a
lot of patience. But I did finally get it to track. First thing I did was
get the Local Osc to track. Then I worked on getting the Mixer and RF Amp
stages to track. I did the L.O. by using a Spectrum Analyzer. I put an
O'Scope probe on the Spec An and just laid the probe near the L.O. to
minimize loading the stage. Then I went back and forth between the High end
and low end alternately adjusting the inductance and trimmers. I was able to
achieve some fine tuning by bending the capacitor plates on the main tuning
cap, another trick I learned working on Navy UHF equipment. But it took a
LOT of fiddling to finally getting it. Then I went onto the Mixer, RF stages
doing the same thing. I did NOT go back and change the L.O. settings. Once I
got the L.O. set I worked on getting the other stages to track the L.O.

It was all fun though, can't do all that fiddling and tweaking with the new
stuff.

John



John R. Schmitz

-----Original Message-----
From: hallicrafters-admin at mailman.qth.net
[mailto:hallicrafters-admin at mailman.qth.net]On Behalf Of DA
Sent: Thursday, January 08, 2004 1:00 PM
To: hallicrafters at mailman.qth.net
Subject: [Hallicrafters] S-36A HF reciever (stuck)

Let me start this one over. My name is Douglas Aiken
and this Hallicrafters "thing" started when I was
10-12 with my dads S-38 which he got when he was 13.
So, now I've started to acquire a few additions in the
hopes of building a late 1940's ham shack. So far the
equipment consists of an ART-13A, a BC-348P, S-20R,
S-38, S-36A and a PM-23 and a HF6V antenna to top it
off.

Now for the specifics...
This receiver seems to have been used in the Navy as
it has USN stamped in several places on the interior.

With the RF section cover removed, the tuning dial
does indeed move the variable capacitor which I had
neglected to mention. What I failed to notice is a
white covered wire that comes off of the 6th disk
(towards the back) of the band selector just below the
last acorn tube is disconnected. This wire is what I
believe is my problem, with just cause. Now I just
have to figure out where it goes.

I have a manual for the receiver which I downloaded
from BAMA, which BTW is of excellent quality.

I have been to
http://www.schmitzhouse.com/Johns_Electronics_11.htm
for some reference, but my interior looks like the one
in the manual not the one he's worked on.

I've referred to the schematics to try to located "the
wire", but considering I'm neophyte with this stuff
it's a challenge. And I've got it into my head to
build a power supply for my ART-13. Everything in
time, need to finish studying for my ticket to.

Anybody in Southern California have one I could look
at?

Thanks,

DA

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