| The complete setup
using the SE-1387/SE-1834 Combo
would have SE-143 RF Tuner operating with three
stages of broadly-tuned RF Amplification, a
grid-leak detector with the SE-1387 providing a CW heterodyne oscillator (manually
tuned on-frequency heterodyne oscillator) and
then two stages of transformer-coupled Audio Amplification. By turning
off the SE-1387, the SE-143 operates as a standard TRF receiver and can
demodulate signals from spark transmitters or Radiophone signals.
Fellow LW enthusiast, Dave Samson, gave me this SE-1387/SE-1834 Combo
about six years ago, in August 2020. Dave shipped it from his QTH in
Western New York out to Nevada along with a FTC/Mackay RC-123. When I
inspected the unit, the first thing I noticed was that it used WE 215-A
tubes and all seven tubes were gone. I didn't have any WE 215-A tubes
left. I had sold most of my collector tubes,...to a tube collector,...and
the WE215-A tubes were part of the sale. I did a visual inspection through the two top
lids but never took the two units out of the cabinet. That resulted in
an assumption that the SE-1387 and SE-1834 were some type of RF
amplifier. Not quite six years went by and I then acquired the SE-143
receiver. In some way, I knew that the SE-1387 and SE-1834 required an
RF Tuner like the SE-143. That piqued my interest enough to disassemble
the unit and see exactly what it was supposed to do.
The Interconnection and Operation
- The SE-143 RF Tuner was directly connected to the SE-1834's three
stage, RF transformer-coupled RF amplifier by connecting the
SE-143 RA and RE terminals to the RECEIVER terminals on the SE-1387. It
was mentioned in the SE-143 manual that since the RA wire is a "grid
connection" it had to be isolated, as much as possible, from other wires
("not bunched with the other wires" was the terminology used.) However,
note that the SE-1387 terminals does provide a grounded SHIELD terminal
implying that the RA/RE SE-143 connection should use a shielded cable.
Internally, the RECEIVER terminals connect directly to the
AMPLIFIER-GRID terminals and are "strapped" to the GRID INPUT of the
SE-1834. This allowed the SE-143 a direct connection via its RA terminal to the
first RF amplifier grid. The SE-143 Secondary LC ground-return is routed
through the pick-up coil in the SE-1387 to allow the heterodyne
oscillator to modulate the incoming signal to the SE-1834 RF amplifier
grid (if the SE-1387 is powered-up.) Since the heterodyne is
modulating the ground-return, there is a wire-wound resistance that's
adjustable to "stabilize" the actual heterodyne versus signal ratio.
The actual practicality of this connection relies on the oscillator
coupling coil having a low enough impedance and that the oscillator has
enough pk-pk voltage output to overcome the losses of this type of
hook-up. As mentioned, this hook-up is implied by the location of the
terminals and, without any documentation, an actual functioning
interconnection has to be determined by experimentation using
operational equipment. Testing has shown that this hook-up works
quite well.
The RF amplifiers were broadly tuned via
three RF transformers that provided four broadly-tuned ranges. This is
essentially also where the incoming tuned radio signal was heterodyned
with the SE-1387's variable-coupled oscillator output to allow detecting CW
signals from VT,
Arc or Alternator transmitters. The output of the 3rd RF amplifier stage was then
routed to the detector stage. The output of the detector was
routed to a two-stage, transformer-coupled audio amplifier.
The audio output was routed to the TEL. terminals. Total gain was
controlled by the filament voltage control and by the STABILIZER
control. The purpose of the switch
RADIO-AUDIO/AUDIO is to allow all filaments to operate in the
RADIO/AUDIO position and turns off the filaments to the Detector tube
and the two AF amplifier tubes in the AUDIO position allowing just the
three RF amplifier tubes to operate (although this seems opposite of
the expected function, measuring the continuity confirmed that the
detector and audio tube filaments are turned off in the AUDIO
position. However, the nomenclature might imply using only the SE-1837 RF amplifiers ahead of the receiver's regenerative detector and audio
stages.) The STABILIZER control is
a wire wound resistance of the SE-143 RE connection terminal (secondary
tuned LC ground return) to the B- line. The FILAMEOSTAT adjusts the
filament voltage on the WECO 215-A tubes (set to 1vdc fil voltage.) For use of the SE-1387/SE1834 combo, the TICKLER
terminals have the strap installed and the AMPLIFIER-GRID INPUT straps
are also installed. If just the SE-1834 was used with an SE-143 RF
Tuner, it would be possible to remove the TICKLER strap and use the
TICKLER connections on the receiver for a regenerative detector. The
RA-RE connections on the SE-143 would then be connected to the SE-1834 GRID INPUT
directly. Again, these are implied connections. An actual functioning
hook-up has to be determined by experimenting with operational
equipment.
There was an SE-1834A version that eliminated
the filament voltage meter (shown in two of the vintage B&W photos further
below.) The Western Electric Co. 215-A tube
- WECO 215-A tubes, also known as VT-5 or D-80039, are very similar
internally to the WD-11 tube. However it's quite probable that the internal design of the later WD-11
that was used in Westinghouse-RCA battery operated Broadcast consumer radios from
1922 up to 1925 was actually based on the 215-A since Westinghouse and
AT&T (Western Electric) were cross-licensed in the GE-RCA "Radio
Group." The
215-A tube envelope and base are significantly smaller than the WD-11.
The tube socket is
unique and only fits the 215-A. Filament specs are 1.0vdc at .25A (WD-11
is 1.1vdc at .25A.) If the filament structure is like the
WD-11/WD-12, then the 215-A uses an iridium-platinum ribbon that's
oxide-coated. The 215-A behaves like a WD-11 in that filament emission
takes place at a very low temperature and low current level (much
lower than the .25A spec.) Most of the time, the 215-A filament isn't
really incandescent at all but the emission is at specifications. In a
day when a typical UV-201 tube required 5vdc at 1amp and the pure tungsten
filament incandesced like a 5 watt lamp, the 215-A and the WD-11 behaved
quite differently with many users unnecessarily increasing the filament
current up to the point of filament incandescent visibility with disastrous results. Plate voltage maximum is +100vdc though usually
the tubes are operated at +40vdc to +60vdc. The amplification factor is
typically about 5 but could go up to 7 or 8 at higher plate voltages
and if the tube has good emission. The 215-A tube was only used for a
short time and was commonly found in the Western Electric Broadcast
Monitoring Superheterodyne Receivers, like the 3-series and 4-series,
also other WE BC monitors and apparently in a hearing testing device. Its common use was in the
period of 1921 up to about 1928 although there are some indications that
the Signal Corps had some use for VT-5/215-A tubes as late as the
early-1940s. Although the WD-11, WD-12, WE239A and, the more
modern replacement, the RCA 864 all have almost identical specs as far
as the tube elements and function, the physical structure of these
electrically-similar tubes is completely different. For initial testing,
since I sold my collector tubes years ago that had included five good
215-A tubes, I'm going to have to buy seven of them,...ouch! The WE215-A
is relatively inexpensive but the
WE239-A is astronomically priced (WE tube dealers,...and for an anemic
triode with an amplification factor of 5???) WD-11/WD-12 tubes
seem to be somewhat fragile because most of the ones I've found had open
filaments. I'm going to use the 864 tube for initial testing. It's a
little more stoutly built and seems to function okay as a substitute.
It's a moderately priced tube but I have several of them that didn't get
included in the collector tube sale. I only used the 864
until I actually had a WE 215-A tube to use.
|
SE-1387 -
Circuit Analysis, Testing, Restoration
There are no schematics available for the
SE-1387 or the SE-1834. In fact, there's no documentation available, at
all. I've had to trace the wiring to see what the
circuits were intended to do when interconnected to an RF tuner like the
SE-143. The circuit is a grid-leak oscillator with tightly coupled grid and plate
coils. The grid coils connect to the variable condenser to allow the LC
to function as a frequency adjustment. The range switch is
double-function and selects both the correct grid coils and the correct plate coils
simultaneously for a specific tuning range. The oscillator output is
coupled by an adjustable "pick-up" coil (COUPLING) that is shielded with
non-ferrous metal to allow magnetic pick-up only. The "pick up" coil
connects in series between the SE-143 secondary LC ground return (lower
Receiver terminal) and the lower Amplifier terminal. My
analysis that the tuned oscillator is to provide an on-frequency
heterodyne for CW reception is based on the increasing use of CW in
place of Spark transmissions at the time and how later "Tracking BFO" TRF receivers were
designed. Vintage photos helped to actually see how these devices were
connected to the SE-143 in particular. However, the final analysis will
be to confirm the SE-1387 does
function as I think it should. This will require a functional WE 215-A tube.
That
should provide functionality for the SE-1387 and, with an oscilloscope and a
LF-MW receiver, I would be able to see and hear the oscillator output.
I've tested all of the coils in the SE-1387 and they all show
continuity, so the testing will begin as soon as a good WE215-A is
purchased and delivered. I did find a broken solder joint that was on
the B+ buss to the plate coils (standard soldering technique of the
1920s using buss wire and "tack soldering" is very prone to breakage,...especially after 100
years on the Planet.) Testing has shown that the implied Filament
voltage at the supply was 2.5vdc however, 2vdc is shown on the front
panel. This level allows the INCREASE pot to
provide +1.0vdc to a .25A load at the tube filaments with the adjustment
at about mid-scale (although the 215-A tube has sufficient emission
well-below the +1.0vdc specification.) Also, A+ is connected to B- and both terminals are
connected to the shield-chassis front panel ground. For initial testing
(before I actually had a 215-A tube,) I used an RCA 864 tube that
I connected into the circuit with clip-test leads. Amazingly, this did
function exactly as expected but the final testing will have to wait for
the 215-A tube to arrive. |
|
The test set-up showing SE-1387
producing a 500kc (600 meters) waveform |
The Test Set Up
- I used an adjustable Lambda power supply with a voltage range
of 0 up to +30vdc at 2.5A. I set the output voltage to +2.5vdc
with the wires connecting to - and + FIL BAT terminals. The B+
power supply is an RCA dual bench supply with a range of 0 to +20vdc
from each supply. I connected the two supplies in series to have +40vdc
B+ with the wires connected to PLATE BAT + and - terminals. The
SE-1387 monitoring was provided by the FNIRSI DPOS350P. This is
a small, tablet-size, modern piece of multi-function test
equipment that runs on a rechargeable battery. I'm using the
oscilloscope to monitor waveforms. Also provided by the DPOS350P
is the waveform frequency and the P-P voltage and a lot of other
parameters of the waveform. Accuracy of the SE-1387 dial is good
with 500kc showing slightly off from 600M. The 2.008mHz waveform
showed 150M on the SE-1387 dial,...not bad for an oscillator
that's over 100 years old. |
Looking over the top of
the SE-1387 showing
the WE215-A tube installed, the 150K grid resistor, the non-ferrous metal
shielded pickup coil and the grid-plate coils |
|
Waveform on Range
A at 150
meters or 2.008mHz
VP/P=230mv |
215-A in
SE-1387 - UPDATE: I've run into this problem many
times, especially on 1920s tubes. When the 215-A tube arrived,
it looked NOS in the original box, but testing the filament
continuity showed it was open. Visual examination with
magnification revealed that the filament was intact. I re-flowed
the solder on the base pins and checked again. This time I had
continuity. I did the same re-flowing technique on the grid and
plate pins. When the 215-A was installed, at first it didn't
oscillate. I increased the filament supply up to +2.5vdc with
the INCREASE control about mid-point for about +1vdc on the
filament. The 215-A started to oscillate. I checked ranges A and
B with no problems in operation. Subsequent testing confirmed
operation on all five ranges. The filament of the 215-A is
oxide-coated so as
the tube is used it should continue to improve emission. Attaining
full
emission usually takes about 30 minutes of operation if the
oxide is thorium-based. From then on, the tube will function correctly
at a somewhat lower filament voltage (unless it's left inoperative for another 100 years.) |
Waveform on Range B at 600 meters or 500kc
VP/P=149mv |
|
SE-1834
Circuit Analysis, Testing, Restoration
Testing the functionality of SE-1834 is much more involved in
that six WE215-A tubes are required for full operation.
Point-to-point DCR testing has shown that both audio interstage
transformers have good primary and secondary windings which is very
helpful (and, yes, I do use that Triplett VOM for continuity testing
as shown in the background of "The Test Set-up" photo above.) The 3rd RF
transformer tests good for all four grid windings and for all four plate
windings (it appears to be a vintage replacement.) The 2nd RF
transformer has all four grid windings showing continuity but two of the
plate windings are open (Band 1 and 4.) The 1st RF transformer
has all four grid winding showing continuity but three of the plate
windings show open (Bands 1, 2 and 3.) All
grid windings in the three RF transformers are good (that's 12 grid
windings total.) Of the twelve plate windings, five are open and
will need to be repaired. Due to the failures in the plate
windings involving all four bands, a bypassing of RF1 and RF2 would only
leave RF3 in operation,...maybe okay for testing but RF1 and RF2 will
have to be repaired for full operation.
Due to the "iron core" type of RF transformers and the method
of construction, any repairs to the windings will be
difficult (but hopefully not impossible.)
All other components of SE-1834 test okay as far as DCR continuity. One
broken solder joint was found. It was a buss wire that connected F+ from
the STABILIZER adjustable resistor to the 3rd RF transformer grid buss
connections.
There are four spring-clip type holders that seem to be for
glass type cartridges for capacitors or resistors. Two are for the Audio
tubes and are from the plate
to B- which would imply they are small value capacitors. One other
spring-clip is connected from the detector grid to the secondary of the
3rd RF transformer. Since there isn't any connection to the detector
grid except through this plug-in cartridge it must be the grid-leak (an
RC component.) The last spring-clip
connects to the TICKLER terminal and to B- indicating this must be
another small value capacitor to bypass any RF to B-. I found two, loose
in the cabinet, glass capacitors that looked similar to large grid-leak
resistors but were marked ".002uf" on the inside. These weren't
installed but were wrapped in plastic and had been placed inside the
cabinet. These are certainly for the small value capacitors needed. I'm
missing a third glass cartridge for the last small value capacitor and a
grid-leak resistor although there should be an associated small value
capacitor which isn't in the circuitry so it must have been part of the
plug-in cartridge. It is possible for the detector to function with just
a capacitor however it will perform better with a high value resistor to
B- (the resistor can be connected in parallel with the capacitor and
"leak" through the secondary winding of the 3rd RF transformer to B-.) It appears that dismounting the tube socket chassis allows
access to most of the components. To ease the process of disassembly and
reassembly, a wiring assembly drawing (not a schematic) had
to be made. Also, close-up photos using a Smart Phone really helps
because the photos can be "super-enlarged" on the computer.
| RF Transformer Coil Rebuild
- Actually, with very little disassembly, the RF transformer coil assemblies can be
removed only requiring unsoldering three connections and removing five
screws and nuts (straps with threaded holes for the transformer
mounting.) I decided to
remove and rebuild one RF coil assembly at a time since that will
require the least amount of disassembly. With the other coil
assemblies remaining in the circuit, I would have a reference for reassembly. The RF Transformer Coils are iron core with about .375" thickness
of laminations. Unfortunately, the four coils appear to all share the same
laminations. The coils themselves look like the typical audio
transformer core only not nearly as wide and with a larger hole in the
center of the core. Just to make taking the RF Coil assembly
apart even more difficult, where the wires exit the wooden frame, those cavities
are filled with sealing wax. It appears that the sealing wax is just in
the cavities where the wires exit and not through-out the coils and
laminations. Once the sealing wax is melted out, then the RF
coil/transformer assembly should come completely apart.
The 1st RF Transformer assembly has three out of the four
Plate-to-B+ windings that are open and one Plate-to-B+ winding
is okay. All Grid-to-A+/B- windings are okay. I tried a
heat-gun to melt out the sealing wax but it isn't a narrow
enough application of heat. A small soldering iron works better
and is able to apply the heat directly where it's needed. Also,
the soldering iron can heat just the individual wires to allow
pulling them out of the sealing wax. Once the sealing wax is
mostly removed and the wires are not being held by the sealing
wax residue, the wooden frame can be removed. This exposes one
side of the RF transformer assembly. The same wax melting
procedure has to be performed to remove the opposite side wooden
frame so that the entire laminations and the four RF cores are
accessible. |
SE-1834 First RF
Transformer Assembly - This is the B+ buss and the A+/B- buss
side that's exposed. The other side is the Grid and Plate
connections that go to the 4-position Band switch. The removed
wooden frame is in the background. |
|
With both wooden frames removed, one can see
that the individual coils can slide out of the laminations.
Inside the center of each coil is a small iron lamination that's
retained using shellac as a gluing agent. This small lamination
provides the complete encirclement of each coil with iron
laminations but also allows for easy extraction of an individual
coil for repair (or replacement back in the 1920s.) The
laminations don't have to have physical contact to provide a
magnetic flux for proper operation.
Although the RF Transformer coils look similar
to audio interstage transformer cores, they aren't the same
internally. The photo to the right shows the difference. The
primary and secondary windings are spaced about .190" apart but
are both wound on the same layer. Each layer builds from the center
outward with just a few to several turns for each layer and for
both the primary and the secondary. This continues building
outward until the correct inductance is reached. Then the
hook-up wires are soldered and the finishing wraps put on the
coil. Primary winding wires exit on one side and the secondary
winding wires exit on the opposite side. That's why when looking
at the RF transformer coil, it looked like the wires were
exiting from the center and outer edge rather than how audio
transformer wires all exit from different layers from center to the
outer layer. Winding these RF transformers is easy in one
regard, each layer only has a minimal number of turns. On the
other hand, one has to do two coils at the same time requiring
two spools of magnet wire.
In testing the DCR of the coils and it appears that
the turns ratio is probably about 1:1. The only good coil in the
1st RF transformer is the LF coil and the primary and secondary
both measure 4400 ohms. If the 1:1 ratio holds true for the
other three coils then the next coil DCR is 2200 ohms, then the
next coil is 750 ohms DCR and the high frequency coil is 350
ohms DCR. I double-checked these DCR reading by measuring the
two remaining RF transformers and the DCR values were consistent
at 4400, 2200, 750 and 350 ohms. After a thorough
inspection, I think the easiest and best method of repair
is to wind entirely new coils. Since both coils are
wrapped the same on each layer, that is why the DCR is
the same for both the primary and the secondary.
However, there are some questions about the DCR
involved,... |
SE-1834 high
frequency 1st RF transformer core removed from the
laminations. It's easy to see how the Primary and
Secondary windings are on the same layer and that the
coils are built from the center of the core out. Also
note the size difference with the LF coil being the
largest. |
|
Questions and a little Math reveals the Impossible - The resistance per foot of 38
gauge magnet wire is .66 ohms. To measure 4400 ohms, the
length of wire necessary would be 6,666 feet and since
there is a primary and secondary winding that would
double to 13,330 feet. The weight of 13,330 feet of 38
gauge copper magnet wire would be around .6 pounds. It's
physically IMPOSSIBLE for that much wire to be placed in the
core of the largest of the cores and that core itself
doesn't weigh even close to half-a-pound. 1922 Federal
T&T plug-in RF
Transformers were wound with resistance
wire that allowed a typical number of turns to the windings
to have a much greater DC resistance than
expected. I scraped off the enamel coating on the RF
transformer core's wire and it was silver color. I measured
approximately 2.0 ohms for a 1" length and that would
equal 12 ohms per foot. For 38 gauge resistance wire
this meets the description of 38 gauge Ni-Chrome wire.
This makes the amount of wire necessary much more
believable. 4400 ohms DCR would take 366 ft of wire and
that's for the largest coil (732 feet for both the
primary and secondary total.) For the highest
frequency coil (smallest) that would take just 29 feet
of wire or 58 feet total for the primary and secondary.
The MAJOR problem is virtually no Ni-Chrome wire is
available with an enamel-type (Foamvar now) of insulated coating.
Insulated Ni-Chrome is a specialty type of resistance
wire and priced well-into the stratosphere (how about
$750 for 100 feet! That would be $4000 for the amount I
need! It must be the cost of Foamvar.) I did find a cheap
source of 38 gauge insulated Ni-Chrome wire but it was
in the Ukraine and on eBay. The bargain-priced Ukrainian
Ni-Chrome is $25 for 25 meters and I need 175 meters
total (575 feet) and that prices out at about $175 and
that includes shipping but
Customs duty or tariffs are an unknown let alone
what the delivery time would be. Also, I have to contact the seller to see
if he can actually supply 175 meters (7x of what he's
selling.) Not the
Best Solution, but a Working Solution -
Essentially, the need for insulated Ni-Chrome for the RF
coils and its "specialty" status means another,
hopefully temporary, solution
is necessary. Luckily, the 3rd RF transformer is
completely intact and can be used. I can disconnect the
grid input wire from the 1st RF Amplifier tube and
disconnect the 3rd RF Amplifier grid wire (that is
coming from the 2nd RF Amplifier.) Then the grid
wire that had been connected to the 1st RF Amp tube can
be routed to the 3rd RF Amp tube. This would allow the
SE-1834 to be used as a broadband four position single RF Amplifier stage,
detector, heterodyne oscillator and two stage Audio
Amplifier. This would end up with the SE-143 operating
as a five-tube TRF receiver including the Heterodyne Oscillator
(which is better than not operating at all.)
If the bargain-priced 38 gauge
insulated-coated Ni-Chrome wire works out then I can then
go ahead and restore the 1st and 2nd RF transformer
assemblies. Incidentally, I've come up with a method
that would only require rewinding the open plate (primary)
windings. The core could actually be bisected down the
middle, separating the primary from the secondary. Then
a new primary wound with the Ni-Chrome wire and that
primary could be "grafted" back onto the secondary part
of the core. This method also divides the amount of
Ni-Chrome wire needed in half, that is, compared to if the core was
entirely rewound (both primary and secondary windings.) The requirement of 575 feet (175
meters) of wire is based on using this solution. |
|
Implementing the SE-1834 Circuit Changes
- All of the circuit changes implemented are easily
reversible. I reassembled the 1st RF Transformer but didn't bother connecting
up each of the cores. They are present, except for the highest frequency
core, inside the assembly. All four of the cores will be
available for rebuilding when the correct type of
Ni-Chrome wire is found. I then reinstalled the 1st RF
transformer assembly back into the chassis of SE-1834. I
didn't bother with fixing the band switch contact arms
for RF1 and RF2 since they aren't going to be
operational anyway. I did realign the contact arms for
RF3 so they make proper contact with operation of the
band switch. Since RF1 was disconnected internally, I
removed the B+ going the RF1. RF2 wasn't taken apart so
I left the B+ connected there. I removed the flexible
wire from RF3 grid and the flexible wire from RF1 grid.
I taped the end of the RF1 grid wire. I installed a 2"
flexible wire extension to the grid wire that comes from
the RA input and soldered that wire to RF3 grid. That
will have the RF tuned signal from the SE-143 connected
to RF3 grid. This completed the circuit changes
necessary for operation.
Testing - I hooked up +2vdc to FIL+
and FIL- at which point the meter indicated FS +2vdc
regardless of the filament adjustment pot (no tubes,
no load.) I checked that I had +2vdc at all
of the tube socket filament contacts. Next, I connected
+40vdc to the B+ and B- and tested the tube socket plate
contacts. The detector plate didn't have B+. The problem
was caused by the very dirty and partially oxidized
TICKLER terminals and the shorting strap. I cleaned all
the metal parts with a brass bristle brush. When
reassembled, I had detector plate voltage at the tube
socket. I installed two 215-A tubes in the AF1 and AF2
amplifier positions. I connected a set of Baldwin Type C
'phones to the TEL terminals. I connected an audio
signal generator set to 400hz to the plate of the
detector tube socket (no detector tube installed.) This
connection placed the audio signal going through the
primary of the first AF interstage transformer. With
+2vdc FIL and +40vdc B+ applied, I heard the 400hz
signal coming through the Baldwin 'phones. This test
showed that the audio section is working correctly.
To test the detector and RF amplifier requires a
modulated RF signal. I first needed to make up a
grid-leak and a small value capacitor for the two clip
connections for the detector "plug-ins." I
installed two more 215-A tubes in the Detector socket
and in the 3rd RF Amplifier socket. I used the HP606B to
apply a 500kc (600M) RF signal modulated with 400hz to
the Grid input terminal of the SE-1834. Voltage was
applied and with the SE-1834 set on the 250M to 750M
band, I heard the HP606B coming through the Baldwin
'phones. I tried the other three ranges and adjusted the
HP606B as needed. All four bands worked.
I moved the SE-1834 and the power supplies to the ham
shack where the SE-143 was set up. I connected the
SE-143 RA to top INPUT terminal on the SE-1387 and SE-143 RE to
the SE-1384
bottom INPUT terminal. I shorted the SE-143 TICKLER
terminals and placed the TICKLER COUPLING at MIN. I had
the SE-143 set to 630kc (KPLY-Reno) so I set the
SE-1834 band switch to 250M-750M and applied voltage.
KPLY came in so strong, the signal was somewhat
distorted. I made a few adjustments to both the SE-143
and the SE-1834 and that got the signal strong without
distortion. I tried a few other daytime AM-BC stations
and all were received easily. Next, I removed the jumper
from the SE-143 TICKLER terminals and the shorting strap
from the TICKLER terminals on the SE-1834. I used two
wires to interconnect the TICKLER coil to the setup.
Although there was an increase in signal, I couldn't get
the detector to oscillate. The connection of RE from the
SE-143 is to B-/A+ through the SE-1387 Coupling Coil and
the SE-1834 STABILIZER variable
resistance. I had the SE-143 connected RE to B-/A+ in my
first setup and I couldn't get the UX-201A tube to
oscillate either. Only when I connect RE directly to the A-
terminal will the SE-143 detector oscillate. There's no
way to make that connection using the terminals as
marked on the SE-1834 BUT if I
hook-up the SE-1387 Heterodyne Oscillator, I should be
able to have a tunable heterodyne available. The gain of
this setup with just one RF amplifier is certainly less
than what it was originally (less selectivity also.)
Still, it will drive a horn speaker to room volume on
AM-BC stations and is quite LOUD on 'phones. In fact, the AM-BC
stations are too loud for 'phones so I had to set up the
WE 10-D horn speaker.
|
|
Using
the SE-143 RF Tuner Receiver with the SE-1387 Heterodyne
Oscillator and the SE-1834 RF Amplifier-Detector-2 stage
Audio Amplifier
The key to getting the SE-1387 and SE-1834 combo
working with the SE-143 is experimentation. Since
there's absolutely no documentation on the SE-1387 or
the SE-1834, I've had to
rely on my circuit analysis, the implied connections
from the arrangement of the terminals and one vintage photograph to
theorize how the entire setup would interconnect and function. Then
experimentation was necessary to see if theory could
actually result in a complete working apparatus. Luckily, it did. |
|
Performance of the
SE-143 with the
SE-1387/SE1834 "Combo" - The SE-1387
RF Driver provides a very strong heterodyne signal that
requires reducing the SE-1387 COUPLING. Using the
letters on the scale will provide the strongest response
from the oscillator which is usually "over-powering."
Reducing the COUPLING will slightly detune the
oscillator frequency which will reduce the pk-pk output
level and then, of course, the tuning dial can be used
to place the heterodyne as desired. Reducing the SE-143
INDUCTIVE COUPLING will also help in reducing the signal
level if necessary and this will also increase
selectivity. TESTING
- To simulate an LF CW signal, I connected the HP606B to
a 50' wire laying on the floor. I set the frequency to 300kc or 1000M with
the amplitude set to 0.3vrms. The SE-143 was picking up
this signal using the outdoor 250' end-fed wire antenna. Audio
output was to the WE 10-D horn speaker. The carrier plus
heterodyne was easily found and tuned for maximum. I
keyed the output of the HP606B to see how true CW would
have sounded and it was pretty nice. Stability of the
heterodyne note is pretty good with maybe a few hz
variance every so often. The heterodyne note quality was
very good. Copying a true CW signal would have been
easy. Also tested reception over the air of Loran-E
100kc and WWVB 60kc. This required changing ranges on
the SE-1387/SE1834 and the SE-143. Heterodyne tuning on
Loran-E and WWVB along with over the air reception
demonstrated that the combination was working on all
tuning ranges. Although all of the signals mentioned
were audible through the WE-10-D horn, it was much better
copy on signals below 500kc when using 'phones. The
WE215-A tubes seem to work best at about 75% of
specified filament voltage, about 0.75vdc results in
good performance.
OPERATIONAL NOTES:
The photo to the right shows the SE-143 and the "Combo" tuned to
and actually receiving WWVB 60kc or 5000M. The filament
supply is set to +2.5vdc and, with the Filament
adjustments on the "Combo," the five WE215-A tubes are
drawing about 900mA (at their rated .25A each the
total current would be 1.25A.) The FILAMENT meter on
the SE-1834 reads +0.72vdc. The Plate supply meters each
show FS at +20vdc for a total of +40vdc plate voltage.
Note that Antenna lead wire is connected to the PRI LOAD
COIL terminal and the ANT is jumped to GR. This connects the Primary LC
for parallel
tuning that allows actually tuning the Primary LC to resonance for
tremendous signal strength. Antenna is the 250'
End-Fed wire and the 'phones are Baldwin Navy Type-C.
Performance of the SE-1834 as a Regenerative
Detector with RF Amplifier and two stages of Audio
Amplification - The TICKLER connection just using the
SE-1834 would require a somewhat different hook-up to
function with the SE-143. The SE-143 RE terminal needs to be
connected directly to the A- on the power supply. I
think that if the setup desired (back in the 1920s)
was for a regenerative detector, then this slight
deviation from the implied "hook-up" would be necessary.
If there was a manual, maybe it did cover this hook-up
when using the SE-143 and the SE-1834 as an RF
Amplifier-Regenerative Detector type setup. Since this
hook-up doesn't use the SE-1387, the COUPLING coil
isn't in the RE wiring so connecting the SE-143 RE directly to A-
won't be a problem. SE-143 TICKLER terminals are
connected to the SE-1834 TICKLER terminals after the
strap is removed. The two straps between the SE-1387 and
SE-1834 terminals also have to be removed. The SE-143 RA
terminal is connected directly to the SE-1834 GRID
terminal. Like any regenerative detector, the SE-1834's
WE 215-A tube ability to oscillate depends on the plate
voltage and the filament voltage plus the position of
the SE-143 TICKLER coil. All of these settings will
interact along with the INDUCTIVE COUPLING setting, the
tuned frequency and the type of antenna used. When
everything is adjusted correctly, the received gain and
sensitivity is incredible. Well, after all, it's a
regenerative detector with an RF amplifier ahead of it
and two stages of audio amplification behind it. |
The SE-143 with
SE-1387/SE1834 "Combo" on top. Receiving WWVB
60kc - 5000M
Antenna lead is connected to PRI LOAD
COIL and ANT jumped to GR for parallel Primary LC Tuning |
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Wireless Specialty
Apparatus version of the SE-1420, probably from a 1920 contract. Tunes
from 300 meters to 7500 meters. Serial
Number: 270R
