One of the Major problems in building a W6TC HBR receiver in the 21st century is acquiring parts. High on the parts priority list are the IF coils which are the basic gain and selectivity blocks for any receiver. Sources for IF coils have literally disappeared and they are no longer available from distributors so this leaves the new builder with only a couple of resource choices:
      a. eBay, either find a HBR receiver to rebuild or possible find the actual IF coils in NOS condition , but be prepared for high inflated prices.

      b. Hamfest flea markets, you might luck out an acquire a HBR part receiver to rebuild and hopefully the IF coils have not been tuned to death by the builder. That's what hams do is tune, and retune, and peak.
One of the advantages of the BC-453 IF coils is that they are not tuned by slugs but by variable capacitors and the variable caps do not wear out or break easily.


           I have never paid more than $10 for a BC-453 parts set that had the coils.

      c. You might try joining some of the Internet lists such as the HBR Receiver List and
Boatanchors List , you can query the list members for assistance.

      The builder might get lucky and find the actual IF coils that were used in the HBR series but the odds are against you. So you have two choices either spend years trying to find the original coils or substitute with other coils or wind your own.

     My best recommendation for the beginners is to utilized Command Set BC-453 IF coils or ARC-5 R-23 coils that are removed from low frequency receivers that have been gutted. Do not destroy a restorable receiver.

   Some advantages of using the BC-453 IF coils are:

       a. They are cheap.
       b. They are fairly easy to acquire at hamfests and eBay.
       c. The coils are rugged and are tuned by internal variable capacitors and do not utilized iron core slugs which often break when tuned. The new builder is going to tune and tune and retune the IF's because that is what hams do and sooner or later the slugs break. With reasonable care the BC-453 IF coil tuning capacitors should last forever.
       d. Each coil has two internal coils that are coupled on a shaft , this spacing between the
coils can be adjusted by an external rod and the spacing varied to each builder individual requirements to increase or decrease selectivity. NO OTHER coils in the HBR series have this advantage.
        e. Both the input and output coils in each assembly can be tuned and peaked from the top of the chassis so you do not have to turn the chassis over to tune the bottom coil.
        f. Remarks d and e lend themselves to easy stagger tuning of the IF's!

    Some disavanges of the BC-453 IF coils are:
       a. They are fairly large in size.
       b. They utilize a 85 Kc center frequency and the original HBR utilized a 75 Kcs IF but this is easy to work around and we will discuss this minor problem else where in these pages.
       c. Mounting can be a small problem but the details will be covered on this page.
       d. You have to find a BC-453 parts set, you certainly do not want to destroy a restorable
radio. Thousands of these sets were highly modified and many were used as "Q5 ers) The sets were simple connected to the 455 Kc IF of smaller 5 tube receivers and then the BC-453 was tuned to 455 Kcs and with its excellent IF enhanced the receiver selectivity etc.
                              

                                      
                                                  The IF coil housing has mounting ears and is easily mounted
                                  using 4-40 hardware. The black cap can be removed for access for tuning.

                                                        
                                                             BC-453 complete schematic.

                                                

                                                     
                                                Another view of the numbering system.

                                                           
                                              Coil spacing adjust rod is in the middle, the two access holes for the
variable caps on on each side. The rod is made out of paper based phenolic and is fairly rugged but
can break off at the top of the can. .

                                                             OUT
                   Note the tuning rod extended slightly and the spacing between the coils has increased.There is a detent for the rod but it also can be operated outside the detent for variable spacing to suit the builder. Total vertical movement is approximately 1/4 inch.

                       Study the two photos above and note that you can't do this variable spacing between coil with Millen IF coils.

                Note:   Speaking of changing IF frequencies, the original HBR had a first IF of 1600 Kcs,  In my area a local broadcast station is on 1600 Kcs so I used a Ist IF of 1.615 to prevent picking up that station. Using the BC-453 IF coils on 85 Kcs requires an crystal injection frequency of 1.700 to reach the IF frequency of 1.615 Kcs.   Sticking with the original IF of 1.600 Kcs you will need a crystal on 1.685 when using the BC-453 coils. 

Before selecting your crystal check for local AM stations in your area because the extended AM broadcast band changed its frequency allocation and moved the upper limit of the AM band plan from 1610 to 1700 kHz. This occurred in 1993.             

                                                          
                                             A test jig for the BC-453 IF coils.
           1. First thing to check is the resistance of each coil. Resistance of the input and output coils should be approximately 130 ohms for Z1(4698) and 35 ohms for Z2(7267) and Z3(4677).
            2. Checking the tuning of the coils guarantees a working coil and also gives you a feel
for the tuning of the coil variable capacitors and you can leave them set centered on 85 Kcs which will help when testing the receiver as the IF will all ready be close.

            3. This photo has the tuning jig in a configuration for injection a 85 Kcs with modulation into the terminal strip on the right. On the left connected to the output is a 1N34 diode detector for feeding a audio amplifier. Just feed in a "modulated" 85 Kcs signal and tune variable caps for max signal on your output.

                                                         
           One of my favorite pieces of test equipment is a Radio Shack amplifiers is a radio shack 277-1008, has its own 9 volt batter and 1 mV sensitivity. See my article in August 2005 issue Electric Radio on its use to as a "Quick and Easy Audio Monitor"

                           
        When tuning the IF coils there is a pointer on the end of each rotor shaft which tells you when the capacitor is at MAX capacitance (IN)  min   capacitance (OUT)   Note: When checking bandwidth of your coils note capacitor location in relation to the very small arrow on top of each rotor. 

                     While testing checking for a peak on the BC-453 coils check for peak at max or highest frequency ( Arrow OUT) and minimum frequency (Arrow IN)The difference should be around 3 Kcs between the two peaks. Due to age of the circuit components and construction of the variables the 85 Kc peak may not be exactly at the mid point of capacitor rotation(arrow sideways) During your actual receiver alignment you may find that you get a better overall response at a frequency other than 85 Kcs such as 86.5 Kcs etc.

                                                           
                     Also take a look (yellow)at the detents for the fiber rod which controls the coil spacing..   

                               
                                 Selectivity Curve using a signal generator and S meter readings.
                                 IF coil rods extended for wide spacing of the two coil windings.