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This began as an attempt to isolate parts differences between the SCR274N receivers, primarily the capacitors, coils, and resistors. The objective was to identify common parts which were interchangeable, as well as those which were not. Once done, it was natural to expand the listing to the corresponding Navy Model ARA and the AN/ARC5 receivers. The lists were developed using the parts list in each manual, with only occasional reference to the schematics due to time limitations. The results are presented below, along with a few of my own observations.
System  0.190.55 Mhz  36 Mhz  69 Mhz  0.521.5 Mhz 
SCR274N  BC453  BC454  BC455  BC946 
ARA  46129  46105  46106  46145 
AN/ARC5  R23  R26  R27  R24 
As you can see, the column sequence above was a result of the nomenclature sequence in the SCR274N series. That is the layout used for each of the lists below. I did not include the 1.53 Mc receivers due to lack of a corresponding receiver in the SCR274N series and page space limitations. Although the SCR274N design derived from the earlier Navy Model ARA, the Air Corps systems were my primary focus so I placed them first.
Component tolerance, resistor power ratings, capacitor voltage ratings, etc. have NOT been addressed! (Any volunteers?)
In the SCR274N list, I've shown and highlighted in my comments the differences between individual receivers. In the ARA and ARC5 lists, the comments highlight differences between ARC5 units and the corresponding ARA and SCR274N sets. Judicious use of a "Hilighter" pen should lead to lists with parts marked which can then be used for a detailed analysis of differences between schematics. Again: Any volunteers?
If you find mistakes, I'd appreciate it if you'd info me so I can correct my list (as
I'm certain you'll correct your own). If
someone wants to use these lists as the starting point for an article addressing receiver
differences in these systems, I would "love" to read the result!
SCR274N Receiver Parts CrossReference
1. Capacitors:  
Symbol  BC453A  BC454A  BC455A  BC946B 
C1  11 pf  11 pf  8.5 pf  11 pf 
C2  15 pf  15 pf  15 pf  15 pf 
C3  100 pf  100 pf  100 pf  100 pf 
C4 A/B/C  346 pf  147 pf  62 pf  346 pf 
C4 D/E  Not Stated  Not Stated  Not Stated  Not Stated 
C4 F/G  Not Stated  Not Stated  Not Stated  Not Stated 
C5  3 uf  3 uf  3 uf  3 uf 
C6 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C7 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C8  200 pf  200 pf  200 pf  200 pf 
C9  40 pf  40 pf  40 pf  40 pf 
C10  N/A  365 pf  240 pf  N/A 
C10 A/B  690 pf (total)  N/A  N/A  670 pf (total) 
C11  3 pf  3 pf  3 pf  3 pf 
C12  180 pf  180 pf  180 pf  180 pf 
C13  17 pf  17 pf  17 pf  17 pf 
C14  180 pf  180 pf  180 pf  180 pf 
C15 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C16 A/B/C  .22/.22/.22  .22/.22/.22  .22/.22/.22  .22/.22/.22 
C17  180 pf  180 pf  180 pf  180 pf 
C18  17 pf  17 pf  17 pf  17 pf 
C19  180 pf  180 pf  180 pf  180 pf 
C20 A/B/C  .05/.01/.05  .05/.01/.05  .05/.01/.05  .05/.01/.05 
C21  17 pf  17 pf  17 pf  17 pf 
C22  180 pf  180 pf  180 pf  180 pf 
C23  180 pf  180 pf  180 pf  180 pf 
C24  200 pf  200 pf  200 pf  200 pf 
C25  .001 uf  .001 uf  .001 uf  .001 uf 
C26  200 pf  200 pf  200 pf  200 pf 
C27  345 pf  345 pf  345 pf  345 pf 
C28  34 pf  34 pf  34 pf  34 pf 
C29  .006 uf  .006 uf  .006 uf  .006 uf 
C30  15 uf  15 uf  15 uf  15 uf 
C31  .001 uf  .001 uf  .001 uf  .001 uf 
C32  5 uf  5 uf  5 uf  5 uf 
C33  3 pf  *  *  * 
C34  N/A  N/A  N/A  N/A 
C35  750 pf  750 pf  750 pf  750 pf 
C36  17 pf  17 pf  N/A  17 pf 
C37  17 pf  17 pf  N/A  17 pf 
C38  17 pf  N/A  N/A  17 pf 
C39  120 pf  N/A  N/A  N/A 
*  Wiring capacitance; less than 2 pf. Comments: a.) C1 for the BC455A is 8.5 pf; the rest are all 11 pf. b.) As expected, C4 A, C4 B, and C4 C vary with tuning range. Unfortunately, the trimmer caps (C4 D,E,F,G) were not specified. c.) I've shown C10 on two lines, to differentiate between the singlecapacitor and dualcapacitor installations. d.) C26 is 200 pf in the BC453A; the rest are 100 pf. e.) C27 is different for each receiver. f.) C33 is 3 pf in the BC453A; the rest use the wiring capacitance (less than 2 pf) instead of an actual capacitor. g.) C36, C37, and C38 are not used in the BC455A. h.) C39 is used in the BC453A across the primary of the RF Amp plate coil; it is not used in the others. 
2. Inductors:  
Symbol  BC453A  BC454A  BC455A  BC946B 
L1  Not Stated  Not Stated  Not Stated  Not Stated 
L2/L3  Not Stated  Not Stated  Not Stated  Not Stated 
L4/L5  Not Stated  Not Stated  Not Stated  Not Stated 
L6/L7  Not Stated  Not Stated  Not Stated  Not Stated 
L8/L9  Not Stated  Not Stated  Not Stated  Not Stated 
L10/L11  Not Stated  Not Stated  Not Stated  Not Stated 
L12/L13  Not Stated  Not Stated  Not Stated  Not Stated 
L14  112 uH  112 uH  112 uH  112 uH 
L15  3 H  3 H  3 H  3 H 
Comments: Same as ARA and AN/ARC5 units. 
3. Resistors:  
Symbol  BC453A  BC454A  BC455A  BC946B 
R1  620  620  620  620 
R2  2 M  2 M  2 M  2 M 
R3  51 K  51 K  51 K  51 K 
R4  620  620  620  620 
R5  150 K  150 K  150 K  150 K 
R6  510 K  200 K  150 K  300 K 
R7  200  200  200  200 
R8  200  200  200  200 
R9  620  620  620  620 
R10  360 K  360 K  360 K  360 K 
R11  100 K  100 K  100 K  100 K 
R12  510  510  510  510 
R13  200  200  200  200 
R14  51 K  100 K  100 K  100 K 
R15  20 K  5.1 K  5.1 K  20 K 
R16  150 K  51 K  51 K  100 K 
R17  150 K  51 K  51 K  100 K 
R18  510 K  510 K  510 K  510 K 
R19  100 K  100 K  100 K  100 K 
R20  2 M  2 M  2 M  2 M 
R21  1.5 K  1.5 K  1.5 K  1.5 K 
R22  7 K  7 K  7 K  7 K 
R23  7 K  7 K  7 K  7 K 
R24  N/A  N/A  N/A  N/A 
R25  N/A  N/A  N/A  N/A 
R26  N/A  N/A  N/A  N/A 
R27  N/A  N/A  N/A  N/A 
R28  N/A  N/A  N/A  51 K 
(Across RF Amp plate coil in broadcast receiver. This
conflicts with use of "R28" as 50K potentiometer in FT260) Comments: a.) R6, R15, R16, and R17 vary with frequency range. b.) R14 is 51K in the BC453A and 100K in the others. c.) R28 is only present in the BC946A. BCxxxA: T1 (output transformer) is high
impedance only. 
Navy Model ARA Receiver Parts CrossReference
1. Capacitors:  
Symbol  46129  46105  46106  46145 
C1  11 pf  11 pf  8.5 pf  11 pf 
C2  15 pf  15 pf  15 pf  15 pf 
C3  100 pf  100 pf  100 pf  100 pf 
C4 A/B/C  346 pf  147 pf  62 pf  346 pf 
C4 D/E  Not Stated  Not Stated  Not Stated  Not Stated 
C4 F/G  Not Stated  Not Stated  Not Stated  Not Stated 
C5  3 uf  3 uf  3 uf  3 uf 
C6 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C7 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C8  200 pf  200 pf  200 pf  200 pf 
C9  40 pf  40 pf  40 pf  40 pf 
C10  N/A  365 pf  240 pf  N/A 
C10 A/B  690 pf (total)  N/A  N/A  670 pf (total) 
C11  3 pf  3 pf  3 pf  3 pf 
C12  180 pf  180 pf  180 pf  180 pf 
C13  17 pf  17 pf  17 pf  17 pf 
C14  180 pf  180 pf  180 pf  180 pf 
C15 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C16 A/B/C  .22/.22/.22  .22/.22/.22  .22/.22/.22  .22/.22/.22 
C17  180 pf  180 pf  180 pf  180 pf 
C18  17 pf  17 pf  17 pf  17 pf 
C19  180 pf  180 pf  180 pf  180 pf 
C20 A/B/C  .05/.01/.05  .05/.01/.05  .05/.01/.05  .05/.01/.05 
C21  17 pf  17 pf  17 pf  17 pf 
C22  180 pf  180 pf  180 pf  180 pf 
C23  180 pf  180 pf  180 pf  180 pf 
C24  200 pf  200 pf  200 pf  200 pf 
C25  .001 uf  .001 uf  .001 uf  .001 uf 
C26  200 pf  100 pf  100 pf  100 pf 
C27  345 pf  180 pf  180 pf  335 pf 
C28  34 pf  34 pf  34 pf  34 pf 
C29  .006 uf  .006 uf  .006 uf  .006 uf 
C30  15 uf  15 uf  15 uf  15 uf 
C31  .001 uf  .001 uf  .001 uf  .001 uf 
C32  5 uf  5 uf  5 uf  5 uf 
C33  3 pf  *  *  * 
C34  N/A  N/A  N/A  N/A 
C35  N/A  N/A  N/A  N/A 
C36  17 pf  17 pf  N/A  17 pf 
C37  17 pf  17 pf  N/A  17 pf 
C38  17 pf  17 pf  N/A  17 pf 
C39  120 pf  N/A  N/A  N/A 
*  Wiring capacitance; less than 2 pf. C27 is across output winding of CW OSC (inside the can). Comments: a.) C27 is 180 pf in the 69 Mc receiver in ARA, where the SCR274N uses 185 pf in the BC455. b.) C35 is not present in ARA receivers; it is 750 pf in all SCR274N receivers. 
2. Inductors:  
Symbol  46129  46105  46106  46145 
L1  Not Stated  Not Stated  Not Stated  Not Stated 
L2/L3  Not Stated  Not Stated  Not Stated  Not Stated 
L4/L5  Not Stated  Not Stated  Not Stated  Not Stated 
L6/L7  Not Stated  Not Stated  Not Stated  Not Stated 
L8/L9  Not Stated  Not Stated  Not Stated  Not Stated 
L10/L11  Not Stated  Not Stated  Not Stated  Not Stated 
L12/L13  Not Stated  Not Stated  Not Stated  Not Stated 
L14  112 uH  112 uH  112 uH  112 uH 
L15  3 H  3 H  3 H  3 H 
Comments: Same as SCR274N and AN/ARC5 units. 
3. Resistors:  
Symbol  46129  46105  46106  46145 
R1  620  620  620  620 
R2  2 M  2 M  2 M  2 M 
R3  51 K  51 K  51 K  51 K 
R4  620  620  620  620 
R5  150 K  150 K  150 K  150 K 
R6  510 K  200 K  150 K  300 K 
R7  200  200  200  200 
R8  200  200  200  200 
R9  620  620  620  620 
R10  360 K  360 K  360 K  360 K 
R11  100 K  100 K  100 K  100 K 
R12  510  510  510  510 
R13  200  200  200  200 
R14  51 K  100 K  100 K  100 K 
R15  20 K  5.1 K  5.1 K  20 K 
R16  150 K  51 K  51 K  100 K 
R17  150 K  51 K  51 K  100 K 
R18  510 K  510 K  510 K  510 K 
R19  100 K  100 K  100 K  100 K 
R20  2 M  2 M  2 M  2 M 
R21  1.5 K  1.5 K  1.5 K  1.5 K 
R22  7 K  7 K  7 K  7 K 
R23  7 K  7 K  7 K  7 K 
R24  N/A  N/A  N/A  N/A 
R25  N/A  N/A  N/A  N/A 
R26  N/A  N/A  N/A  N/A 
R27  N/A  N/A  N/A  N/A 
R28  N/A  N/A  N/A  51 K 
(Across RF Amp plate coil in broadcast receiver. This
conflicts with use of "R28" as 50K potentiometer in FT260) Comments: a.) R6, R15, R16, and R17 vary with frequency range. b.) R14 is 51K in the BC453A and 100K in the others. c.) R28 is only present in the BC946A. 
AN/ARC5 Receiver Parts CrossReference
1. Capacitors:  
Symbol  R23  R26  R27  R24 
C1  11 pf  11 pf  8.5 pf  11 pf 
C2  15 pf  15 pf  15 pf  15 pf 
C3  100 pf  100 pf  100 pf  100 pf 
C4 A/B/C  346 pf  147 pf  62 pf  346 pf 
C4 D/E  Not Stated  Not Stated  Not Stated  Not Stated 
C4 F/G  Not Stated  Not Stated  Not Stated  Not Stated 
C5  3 uf  3 uf  3 uf  3 uf 
C6 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C7 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C8  200 pf  200 pf  200 pf  200 pf 
C9  40 pf  40 pf  40 pf  40 pf 
C10  N/A  365 pf  240 pf  N/A 
C10 A/B  690 pf (total)  N/A  N/A  670 pf (total) 
C11  3 pf  3 pf  3 pf  3 pf 
C12  180 pf  180 pf  180 pf  60 pf 
C13  17 pf  17 pf  17 pf  17 pf 
C14  180 pf  180 pf  180 pf  180 pf 
C15 A/B/C  .05/.05/.05  .05/.05/.05  .05/.05/.05  .05/.05/.05 
C16 A/B/C  .22/.22/.22  .22/.22/.22  .22/.22/.22  .22/.22/.22 
C17  180 pf  180 pf  180 pf  180 pf 
C18  17 pf  17 pf  17 pf  17 pf 
C19  180 pf  180 pf  180 pf  180 pf 
C20 A/B/C  .05/.01/.05  .05/.01/.05  .05/.01/.05  .05/.01/.05 
C21  17 pf  17 pf  17 pf  17 pf 
C22  180 pf  180 pf  180 pf  180 pf 
C23  180 pf  180 pf  180 pf  180 pf 
C24  200 pf  200 pf  200 pf  200 pf 
C25  .001 uf  .001 uf  .001 uf  .001 uf 
C26  200 pf  100 pf  100 pf  100 pf 
C27  345 pf  180 pf  180 pf  335 pf 
C28  34 pf  34 pf  34 pf  34 pf 
C29  .006 uf  .006 uf  .006 uf  .006 uf 
C30  15 uf  15 uf  15 uf  15 uf 
C31  .001 uf  .001 uf  .001 uf  .001 uf 
C32  5 uf  5 uf  5 uf  5 uf 
C33  *  *  *  * 
C34  N/A  N/A  N/A  N/A 
C35  100 pf  100 pf  100 pf  100 pf 
C36  17 pf  17 pf  N/A  17 pf 
C37  17 pf  17 pf  N/A  17 pf 
C38  17 pf  17 pf  N/A  17 pf 
C39  N/A  N/A  N/A  120 pf 
C40  100 pf  100 pf  100 pf  100 pf 
C41  100 pf  100 pf  100 pf  100 pf 
C42  N/A  3 pf  2 pf  120 pf 
*  Wiring capacitance; less than 2 pf. C27 is across output winding of CW OSC (inside the can). Comments: a.) C10 (single or dual) went from mica to ceramic capacitors in January of 1945. b.) C12 is 60 pf in the R24; all other systems used 180 pf. c.) C26 is 200 pf in the R24, but 100 pf in the other systems. d.) C27 is 180 pf in the R24 and 46106, but 185 pf in the BC455. e.) C33 uses wiring capacitance in the R23 where real caps are used in the BC453 and 46129. f.) C35 is 100 pf in the ARC5 receivers, omitted in ARA, and 750 pf in the SCR274N receivers. g.) C39 is omitted in the R23 (present in 46129 and BC453) and inserted in the R24 (omitted in 46145 and BC946). h.) C40, C41, and C43 are all present in the ARC5, but not in ARA or SCR274N. 
2. Inductors:  
Symbol  R23  R26  R27  R24 
L1  Not Stated  Not Stated  Not Stated  Not Stated 
L2/L3  Not Stated  Not Stated  Not Stated  Not Stated 
L4/L5  Not Stated  Not Stated  Not Stated  Not Stated 
L6/L7  Not Stated  Not Stated  Not Stated  Not Stated 
L8/L9  Not Stated  Not Stated  Not Stated  Not Stated 
L10/L11  Not Stated  Not Stated  Not Stated  Not Stated 
L12/L13  Not Stated  Not Stated  Not Stated  Not Stated 
L14  112 uH  112 uH  112 uH  112 uH 
L15  3 H  3 H  3 H  3 H 
Comments: Same as SCR274N and AN/ARC5 units. 
3. Resistors:  
Symbol  R23  R26  R27  R24 
R1  1 K  620  620  620 
R2  2 M  2 M  2 M  2 M 
R3  51 K  51 K  51 K  51 K 
R4  620  620  620  620 
R5  510 K  510 K  510 K  510 K 
R6  510 K  200 K  150 K  300 K 
R7  200  200  200  200 
R8  200  200  200  200 
R9  1 K  620  620  620 
R10  360 K  360 K  360 K  360 K 
R11  510 K  10 K  10 K  510 K 
R12  390  390  390  390 
R13  2 M  510 K  510 K  510 K 
R14  100 K  100 K  100 K  100 K 
R15  20 K  5.1 K  5.1 K  20 K 
R16  300 K  51 K  51 K  300 K 
R17  N/A  51 K  51 K  100 K 
R18  510 K  510 K  510 K  510 K 
R19  150 K  100 K  100 K  150 K 
R20  2 M  2 M  2 M  2 M 
R21  1.5 K  1.5 K  1.5 K  1.5 K 
R22  7 K  7 K  7 K  7 K 
R23  7 K  7 K  7 K  7 K 
R24  3 K  3 K  3 K  3 K 
R25  N/A  N/A  N/A  N/A 
R26  150 K  N/A  N/A  150 K 
R27  100 K  N/A  N/A  100 K 
R28  1 K*  N/A  N/A  1 K* 
R29  N/A  2.4 K  2.4 K  N/A 
R30  N/A  100 K  100 K  N/A 
R31  N/A  100 K  100 K  N/A 
R32, R33, R34  N/A  N/A  N/A  N/A 
R35  N/A  N/A  N/A  51 K 
R36  N/A  N/A  N/A  N/A 
R37  200  200  200  200 
*  R28 in early production units only. Comments: a.) R1 is 1K in the R23, but 620 ohms in 46129 and BC453. b.) R5 is 510K in ARC5, but 150K in ARA and SCR274N. c.) R9 is 1K in R23, but 620 ohms in 46129 and BC453. d.) R11, R12, and R13 are radically different in ARC5. e.) R14 is 100K in R23, but 51K in 46129 and BC453. f.) R16 is 300K in R23, but 150K in 46129 and BC453. g.) R17 is omitted (?) in R23 but present in 46129 and BC453. h.) R19 is 150K in R23, but 100K in 46129 and BC453. i.) R24 is 3K in ARC5, but omitted in ARA and SCR274N. j.) R26 and R27 are only present in ARC5 receivers. k.) R28 is 51K in ARA and SCR274N broadcast receivers, but appears as 100K in R23 and R24 early production units only. l.) R29, R30, R31, R35, and R37 are found only in ARC5 units. 
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