PRC-6 Battery Box

               Revised 10/31-2010

Note: You have enough time to get your PRC-6 powered up in order to be at the Military Radio Collector Association Meet next September at Gilbert.

                                Link to MCRA

MISSION: To power up that PRC-6 and get it to the military meet or hamfest. Remember anyone can take and operate a PRC-68 sissy radio at a meet or hamfest but it takes a man to operate and haul this thing around all day.  .   . And just think you can leave the PRC-6 on your seat as you drive through Philadelphia to ward off car jackers.

WARNING: I have had several reports of Energizer batteries overheating when used in parallel. Please make sure that the batteries that you use are fresh, same date code etc. I suggest testing them for equal voltages under load before using them in the battery pack. I would not mix different brands of cells. Some of the overheat reports resulted when the Energizer C cells was used. During periods when your PRC-6 is not used I would remove the pack from the radio.

UPDATE: May 2006, I have also experienced the same with C cells in a PRC-6 but they were not the Energizer brand but were cheaper batteries. One cell shorted out internally and drew the other batteries down which created a lot of heat.

Please read Energizer's Product Safety sheet at: http://data.energizer.com/PDFs/carbonzinc_psds.pdf

    Overview: The PRC-6 requires two high voltages:   90 volts and 45 volts.    In addition it requires a filament voltage of 1.5 volts. A bias voltage of 4.5 volts is also needed for the frequency control and audio circuits. Off the shelf batteries will be used in a unique two tiered battery box that is easy to construct, service, and is robust in construction. Four (4) C cells
are wired in parallel for the 1.5 volts. Three(3) AAA cells are
                                         used for the bias supply of 4.5 volts.

 

 

Update: October 2010. I've included an addtional page containing Gene Smar's AD3F battery pack which uses simpler construction .Look over the entire section before your decide which type of pack you are going to construct. Link at the end.

   The idea for double decking of the batteries was originally published by Dave Storm. You might want to check his article on the Army Radios Sales site in the UK and look at his ideas. Look for his "Power UP" article under "Your Articles" in the index. Link at the end.

                       

                   

 

   Basically the box is in two tray sections, high voltage on the top and low voltages on the bottom. The upper "straddle tray" holds the 9 volts batteries can be removed for service. The "straddle tray" straddles and fits on top of the C cells below. Simple spade type connectors are are used between the trays..
                                              


    WARNING:
Even though we are dealing with those harmless 9 volt batteries , when they are wired in series the voltage is over 90 volts and you can shock the xiss out of your self if you forget or get careless. Do not test the 90 volt battery string with your tongue.

:   The bottom sections holds 4 "C" cells wired in parallel and the 4.5 volt bias pack consisting of 3 AAA batteries. Don't worry about the small size of the AAA batteries, they will hold up as the bias circuit draws less then 10 microamps. A standard 7 pin vacuum tube*  socket is used for the pack connector.

                                  * That hollow thing that lights up.

   The "Main Tray"consist of a long tray with attached sides. This view is of the bottom of the main tray showing the bottom over lapping edges of the sides.
Comparison of the original battery to the "main tray" assembly. Arrows point to tie points for providing strain relief for the wiring. The fabricated sides are shown but are not attached yet.
 
  Shown are the dimensions for the main tray, the idea is to make the tray as large as possible and fill up the radio, this leaves more room for the batteries. So make this tray as wide and as long as possible. Fabricate all of the sections from .025 aluminum sheet available from your local home supply store. If you don't have a sheet metal brake see my "BC-611 battery box" for bending techniques using a bench vice.
                                               BC-611 CLICK HERE
    

    Sides for the "Main Tray", You might want to round the top corners after bending.
  
    The "Straddle Tray" will fit down inside the "Main Tray". Notch out the front of the tray to allow room for the wiring.
    

    The U shaped "9 volt tray" holds 10 of the 9 volt batteries and is attached to the top of the "Straddle Tray".
   

    The "9 volt tray" attaches to the top of the "Straddle Tray".
   The upper straddle tray assembly will slide into the lower assembly. The rear cover for the radio keeps everything in place.
  A standard 7 pin socket is used for the connector. Notice the "Stop Nuts" used for the assembly. A hot air gun will be used on the heat shrink to shrink it.
The connector is mounted in the top of the main tray. There is room beside the C cell holders for a distribution board and the AAA bias battery holder.

 

  If you don't have a "Unibit" to drill holes you might try and find one,it makes a nice neat hole and you just keep drilling until the socket fits. If you drill too far you wind up with a very big hole but it will still be neat.

   When you fabricate the "9 volt tray" you want a tight fit so that the 9 volt batteries (total of 10) will remain in place. You will not need any 9 volt battery holders. Don't forget to put the connector on the 9 volt batteries when doing your trial fitting. The rear cover for the radio will cover the top of the tray and keep the batteries in place.
  This is the top of the "straddle tray" , the cut out section allows for wire connections to pass through the tray to the bottom distribution board. The top U shaped "9 volt tray" has a small end piece configured to keep the 9 volt batteries from from sliding forward out of the tray during maneuvers at the hamfest such as dropping the radio while in the hamburger line.
   The "9 volt" tray also has a small piece of aluminum fabricated as a end piece at the bottom of the tray for the same reasons as given before but you can include the hot-dog line.
   There is space between the ends of the 1.5 volt battery holders and the sides of the main tray but I would insulate the rivets on the side of the battery holders anyway.
   I fabricated a distribution board for the wiring. The Dremel Tool comes in handy for creating wiring pads to organize your wiring.
  I provided extra pads on the board for future expansion. What expansion?    How about a tone board for 150 cycles.
  There is plenty of room at the top of the tray for the main 7 pin connector and the connector wiring.
Looking at the "bottom" of the tube socket, the pin numbers are shown.



                               Actual wiring diagram taken from the manual
 The 9 volt wiring harness with the connectors in series. Notice the tap for 45 volts on the string of connectors. An additional lead was soldered on each end for the spade connectors and it was covered and reinforced with heat shrink.

  Install a tap for the 45 volts. Insulate connections with heat shrink**

                                                            

                                         ** Therapist for heat.

      Their are many styles of 9 volt battery connectors , I prefer the more rugged type, buy em at the hamfest or its Rad Shack part number 270-324(package contains 5 connectors ), very nice rugged connector.

  Common spade connectors are used for connections between the 9 volt battery removable tray and the distribution board. If you don't have a real crimper tool, get one while you are Rad Shack.

 



    The spade lugs help you disconnect the 9 volt tray for service. Or if you don't want to bother then just use long leads.
  Cover the "distribution board" with a piece of cardboard and lay the AAA Bias pack on top. Hide the emergency hamfest money under the card board.
  

                          Spade lugs are covered with clear insulation.
   I love the smell of  zink chromate  in the morning.
  Finish the project with a coat of Olive Drab.
  The upper tray slides into the lower tray to straddle the C cell packs.
   The spade connectors with clear insulated sleeves stow in the sides between the "9 volt tray" and the main tray.
When you put on the rear cover it will hold the entire assembly in place and the 9 volt batteries will not go any where.
  

   Here is a nice shot of the interior with the cover on, as you can see the entire battery assembly fits perfectly.
   A Secret placard was placed into the radio under the battery box on top of the radio battery card.  Contains vital information for the radio and the distribution board. (Right click on the chart picture and print)
                               

                                             Tray ready for insertion.

  Note that there is plenty of room for the main tray 7 pin connector and you can hide a P-38* in there if you want.

                                    * Used to open the Lima Beans in C rations.

 

                                

 

Nice fit and plenty of room. Ready for the MRCA Military Radio Meet or the "Cold War Net" at Dayton.

                    Note New Link to AD3F's battery pack.   

   Page 2, Gene Smar's AD3F battery pack construction. Simple and elegant!

           

                                 Army Radio Sales UK                                                       

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