This began as an attempt to isolate parts differences between the SCR-274-N 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/ARC-5 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 |
0.19-0.55 Mhz |
3-6 Mhz |
6-9 Mhz |
0.52-1.5 Mhz |

SCR-274-N | BC-453 | BC-454 | BC-455 | BC-946 |

ARA | 46129 | 46105 | 46106 | 46145 |

AN/ARC-5 | R-23 | R-26 | R-27 | R-24 |

As you can see, the column sequence above was a result of the nomenclature sequence in the SCR-274-N series. That is the layout used for each of the lists below. I did not include the 1.5-3 Mc receivers due to lack of a corresponding receiver in the SCR-274-N series and page space limitations. Although the SCR-274-N 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 SCR-274-N list, I've shown and highlighted in my comments the differences between individual receivers. In the ARA and ARC-5 lists, the comments highlight differences between ARC-5 units and the corresponding ARA and SCR-274-N sets. Judicious use of a "Hi-lighter" 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!

SCR-274-N Receiver Parts Cross-Reference

1. Capacitors: |
||||

Symbol |
BC-453-A |
BC-454-A |
BC-455-A |
BC-946-B |

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 BC-455-A 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 single-capacitor and dual-capacitor installations. d.) C26 is 200 pf in the BC-453-A; the rest are 100 pf. e.) C27 is different for each receiver. f.) C33 is 3 pf in the BC-453-A; 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 BC-455-A. h.) C39 is used in the BC-453-A across the primary of the RF Amp plate coil; it is not used in the others. |

2. Inductors: |
||||

Symbol |
BC-453-A |
BC-454-A |
BC-455-A |
BC-946-B |

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/ARC-5 units. |

3. Resistors: |
||||

Symbol |
BC-453-A |
BC-454-A |
BC-455-A |
BC-946-B |

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 FT-260)Comments:a.) R6, R15, R16, and R17 vary with frequency range. b.) R14 is 51K in the BC-453-A and 100K in the others. c.) R28 is only present in the BC-946-A. BC-xxx-A: T1 (output transformer) is high
impedance only. |

Navy Model ARA Receiver Parts Cross-Reference

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 6-9 Mc receiver in ARA, where the SCR-274-N uses 185 pf in the BC-455. b.) C35 is not present in ARA receivers; it is 750 pf in all SCR-274-N 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 SCR-274-N and AN/ARC-5 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 FT-260)Comments:a.) R6, R15, R16, and R17 vary with frequency range. b.) R14 is 51K in the BC-453-A and 100K in the others. c.) R28 is only present in the BC-946-A. |

AN/ARC-5 Receiver Parts Cross-Reference

1. Capacitors: |
||||

Symbol |
R-23 |
R-26 |
R-27 |
R-24 |

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 R-24; all other systems used 180 pf. c.) C26 is 200 pf in the R-24, but 100 pf in the other systems. d.) C27 is 180 pf in the R-24 and 46106, but 185 pf in the BC-455. e.) C33 uses wiring capacitance in the R-23 where real caps are used in the BC-453 and 46129. f.) C35 is 100 pf in the ARC-5 receivers, omitted in ARA, and 750 pf in the SCR-274-N receivers. g.) C39 is omitted in the R-23 (present in 46129 and BC-453) and inserted in the R-24 (omitted in 46145 and BC-946). h.) C40, C41, and C43 are all present in the ARC-5, but not in ARA or SCR-274-N. |

2. Inductors: |
||||

Symbol |
R-23 |
R-26 |
R-27 |
R-24 |

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 SCR-274-N and AN/ARC-5 units. |

3. Resistors: |
||||

Symbol |
R-23 |
R-26 |
R-27 |
R-24 |

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 R-23, but 620 ohms in 46129 and BC-453. b.) R5 is 510K in ARC-5, but 150K in ARA and SCR-274-N. c.) R9 is 1K in R-23, but 620 ohms in 46129 and BC-453. d.) R11, R12, and R13 are radically different in ARC-5. e.) R14 is 100K in R-23, but 51K in 46129 and BC-453. f.) R16 is 300K in R-23, but 150K in 46129 and BC-453. g.) R17 is omitted (?) in R-23 but present in 46129 and BC-453. h.) R19 is 150K in R-23, but 100K in 46129 and BC-453. i.) R24 is 3K in ARC-5, but omitted in ARA and SCR-274-N. j.) R26 and R27 are only present in ARC-5 receivers. k.) R28 is 51K in ARA and SCR-274-N broadcast receivers, but appears as 100K in R-23 and R-24 early production units only. l.) R29, R30, R31, R35, and R37 are found only in ARC-5 units. |

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