previous <<==>> next

TELEGRAPHY
Have a look at the WESTON ELECTRIC TELEGRAPH TEST UNIT ...

TG-5-B
WWII  U.S. ARMY / NAVY  FIELD  TELEGRAPH  SET
RESTORATION



This SKETCH is from the TG-5-B Manual ...



The WIRING DIAGRAM is in the Lid ...



There are Slots for ...
The  LINE BATTERY  (  3_3/8"  x  2_1/2"  x  1_15/16" )   of   22.5 Volt
and the  LOCAL BATTERY  made of   2  x  1.5 Volt  »D«-Cells

Because the original-sized battery is no longer available,
I made my LINE BATTERY-PACK out of a "dead" laptop Li-Ion-Battery ...



5  x  3.7 Volt  =  18.5 Volt  Battery with a polarized connector-pair works well.

The Picture of the closed Steel Box:  W = 6_3/4"  x  D = 4"  x  H = 4_7/8"



and its PLAQUE ...



The RECEIVER RELAY was disassembled and not working:



... The missing SPRING had to be replaced & put in an Insulation Pipe ...



... It holds the MIDDLE CONTACT in place & "in force" by the SENSOR-ADJUSTER.



... To center the Middle Contact, the HOLDERS had to be bent !!!

After solderings, correcting wrong connections, cleaning contacts ...
The TG-5-B works now with the BELL - but not with the "INTERRUPTER"!

Disassembling the "INTERRUPTER" showed...
Left Half is an EARPHONE - Right Half is a MICROPHONE.
Repairing the Broken Wire in the Earphone was a strait foreward job ...



... ( see below ) - TEST with MUSIC was successful !

But the MICROPHONE ( right ) needs further attention:
Opened ( with a metal sheet ) the Microphone's Diaphragm-Ring ...



... Added CARBON PARTICLES (from another microphon) & COTTON   ...   ! ATTENTION !
The AMOUNT of both and the TENSION of the DIAPHRAGM-RING
are VERY CRITICAL PARAMETERS !!!

A DIAGRAM of a MORSE TRAINER ( W.W.Diefenbach »Morselehrgang« 1956 ) left ...

 

... USED AS THE TEST CIRCUIT   ...   and the re-assembled "INTERRUPTER" Unit right.
After TRIAL & ERROR ... Now the »TG-5-B« works again - "YAHOO!"

PS.:   Sometimes the "INTERRUPTER" needs a "Wake-Up!" KNOCK

Authentic WWII HEADPHONES were found in a Flea Market in Berlin ...



... and its missing "ARCH"
is home-made
from WIRE-HANGERS!

My "Morse Trainer"
from the '50s
will become the
PARTNER STATION ...
   



But not as simple as thought: The loop current is under 10 mA !
A  3-mA-RECEIVER  is made out of ...



... a "Polarized Relay",  SIEMENS  T.rls.63a

HOW  A  POLARIZED  RELAY  WORKS ?
( Adapted from SIEMENS / 1961 "Einf.i.d.Fernsprechtechnik", p.100 )



The MAGNETIC ACTUATOR is embedded in a PERMANENT MAGNET.
Without current, the actuator rests either left or right.
A POSITIVE current through the spool enhances the magnetic field of the
permanent magnet on its LEFT side and weakens it on the right side.
A NEGATIVE current enhances the magnetic field on the RIGHT side
and weakens it on the left side - and therefore
the ACTUATOR FLIPS to the OPPOSITE POLARITY and RESTS THERE.
( Polarized relays may have more spools for special control patterns )

HOW  TO  MAKE  A  RECEIVER  RELAY  OUT  OF  IT ?
(1st) Set its contacts asymmetrically to get a definite rest-position
(2nd) Connect all ( if ) windings in a row to have the maximal sensitivity
(3rd) A POSITIVE CURRENT flips the actuator, the CONTACT will be closed,
and now the receiver relay can be used in the rhythm of the Morse Code.

The  WIRE  DIAGRAM  of  the   P A R T N E R    S T A T I O N
for  the  » TG-5-B «  ( see top )  WWII   TELEGRAPH  SET ...



... with a "Graetz Bridge" because the polarized relay is (+/-) sensitive!

Ready to entertain neighbor's kids with a "Real Telegraph Line"

HOW TO USE THE »TG-5-B« AS A MORSE-TRAINER ...
                  Back to the Telegraph Main Page ...
impressum:
***************************************************************************
© C.HAMANN        http://public.beuth-hochschule.de/~hamann        04/09/13