Army Radio Sales Co. :: Command Sets, List of Differences

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. BC-xxx-B: T1 has both high and low impedance taps; set at factory for high-z. BC-xxx-C: ?? (unknown differences). BC-xxx-D: ?? (unknown differences). BC-xxx-E: T1 has high/low taps; set at factory for low-z.

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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