GN-45 Modified for BC-474 Power                   




     The BC-474 transmitter section was "designed" to be powered by the hand cranked GN-44 with the receiver option of being powered by the GN-44 via the FL-10 filter or by a battery similar to the BA-48. The GN-44 generator set is fairly rare but the GN-45 used with the SCRX-284/BC-654 can be found and easily modified to power the BC-474. (Modification is reversible)





       Using the GN-45 is not technically correct but it does make a nice "working" display during Military Rallies and Events. Visitors enjoy cranking the generator.


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       In order to provide proper bias to the receiver audio section the HV section of the power supply B - (B minus) must be above ground. The GN-44 hand crank generator diagram shown above demonstrates the B- (B minus) wiring. The GN-44 is fairly rare but the GN-45 can be used as a substitute and a suggestion for a modification is shown below.
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      The GN-45 High Voltage B minus is at ground potential. When using the GN-45 generator to provide voltages to both receiver and transmitter on the BC-474 the B- (B minus) terminal of the generator must be above ground.
                       NOTE: When using the GN-44 or the GN-45 to power the BC-474 receiver the FL-10 filter box must be utilized to provide proper filament voltage and B plus voltages to the receiver.

                 More information on the FL-10 filter and different BC-474 power options can be found in another section.
                            Link to BC-474 power options is at the bottom.


                      The basic mod is to isolate the ground return (B -) of the generator terminals and lift the minus side of the 4 uF filter capacitor from ground. Most generators have a leaky 4 MFD capacitor and it may need replacement. Connect the lifted end of the capacitor (5.C.1) direct to the B- terminal of the generator. Connect the B- of the generator to the main 8 pin connector 5.K.1 pin 3 via a terminal on the relay. Note: The relay is not used or powered for BC-474 operation the terminal is used as a convenient tie point.  Add a jumper on relay 5.E.2 to bypass the relay and provide the High Voltage (500V) to pin 8 of the connector.




        Shown above on the right is the High Voltage minus (B -)terminal with new wiring. One wire goes to the filter capacitor and the other wire to pin 8 of the main connector.


NO OUTPUT ?         Be sure and clean the communicator on the low voltage side as the windings may not be getting enough excitation. Any dirt or residue can prevent proper excitation. I usually use one of those 3M green pads for cleaning.


          Shown above the "Leaky" filter capacitor (bottom) has been replaced and a modern cap cable tied in place. A white/blk wire connects the capacitor to the minus terminal of the generator. The relay shown above (upper right) is not used or powered for BC-474 operation. The brown wire connects the minus terminal of the generator to the relay terminal which is used as a tie point to pin 8 of the main connector. The voltage regulator shown in the center is still used and is not disturbed.

                   A small interface box was used to connect the 4 pin BC-474 cable to the the GN-45 using a fabricated cable and connector. A 5 K resistor was used to lower the B plus. A 6.3 volt light was wired to the 6 volt output. Remember to provide proper voltages to the receiver filaments and plates you must use a FL-10 filter.     Link for info on the FL-10 and other BC-474 power options is at the bottom.

                        A connector was fabricated from phenolic and brass tubing.

          The  small package allows more options for your GN-45/BC-474.  The generator 8 pin male connector is not rare and can be purchased from the usual suppliers. The 4 pin connector for the BC-474 power cable is home brew.       

                                  Ready for the Rally

                     BC-474 FL-10 filter and power options

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