RCA-Victor-Co-Inc-BT-42 电路原理图.pdf

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1、MANUAL OF 1940 MOST POPULAR SERVICE DIAGRAMS MODEL BT-42 Alignment Procedure Output Meter Alignment. If this method is used, connect the meter across the voice coil, and, turn the receiver volume control to maximum. Test-oscillator.For all alignment operations, keep the output as low as possible to

2、avoid a-v-e action. Pre-setting Dial.With the gang condenser fully out of mesh, the indicator should point to the extreme right (high frequency) mark on the dial scale. Precautionary Lead Dress. 1. All filament (brown) and B-f- (red) leads must be dressed away from unshielded I.F. coil. 2. Green gri

3、d lead of 1A7G tube to be twisted around antenna (blue) lead for capacity coupling. 3. Red and brown battery cable leads to be dressed and held against front apron with tape. CAUTION.When ready to install or replace batteries or tubes or to make any repairs or changes, be sure to turn off power swit

4、ch. Steps Connect the high side of test-* oscillator to Tune test-osc. to Turn Radio Dial to- Adjust the fol lowing for max. peak output 1 1A7G lst-Det. .grid cap, in series with .01 mfd. 455 kc Quiet point at 550 kc End of Dial C8, C9, CIO. Cll (1st and 2nd I-P transformers) 2 Antenna lead (blue) i

5、n series with 100 mmfd. 1,500 kc 1,500 kc C5 (oscillator) S 600 kc 600 kc Ll (antenna)* 4 1,500 kc L_ 1,500 kc C) (antenna) * When adjusting LI (antenna), trimmer C3 should be in a minimum capacity position (unscrewed). battery cable plug COMPILED BY M. N. BEITMAN, SUPREME PUBLICATIONS 收音机爱 好者资料库 Ra

6、dioFans.CN PAGE 460-0 MODELS BK -42 and BT -42 Chassis No. RC -408C RC -408A Four -Tube, Single -Band, Battery -Operated Superheterodyne Receivers Model BK -42 (RC -408C). Electrical and Mechanical Specifications I.,1 II e ;-1D.1,720 kc 455 kc Intcir,u-,li:,te Ft e,intair RCA. TUBE (OM P LE M E N T

7、ll) R(.A-1:17-(; lst-Bet.-nsc. (2) l2(: -1N5-(; I -F Amplifier (:) RCA -1115-G 2nd-Det., A- F, and A.V.C. (41 RCA -1Q5 -G Output BATTERIES REQUIRED (t UT) EN T CONSEAtPTION -A, D.24 antlrc_-11. lD POWER nITPIT Undistorted Maximum No. 748 or equivalent). milliamperes. LOUDSPEAKER BT -42 0.15 watt 0.2

8、5 watt Type 5 -inch permanent -magnet dynamic Voice -coil Impedance 3.3 ohms at 400 cycles MODEL BK -42, Technical Information and Service Data: Refer to Service Data on Model BT -42 and the following parts: Stock No. 12635 Capacitor -1,000 mmfd. (C16) SPEAKER ASSEMBLY, BK -42 (84649-2) 6 -in. P. M.

9、 34507 Cone-Speaker cone and voice coil 34508 Transformer-Output transformer: MODELS BK -42, BT -42 Oscillator Grid Resistor: In some production, the oscillator grid re- sistor (R1) is changed from 220,000 ohms to 150,000 ohms (Stock No. 14020). Did Drive Slippage, or Cord Breakage: In cases where a

10、bnormal slippage or break- age of the dial cord is experienced, the follow- ing corrective measures are suggested: SLIPPAGE: Slippage may be due to one or more of the following conditions: (a) Chassis mounted too far into cabinet caus- ing dial pointer to rub against cabinet. (h) A bent cord drum to

11、uching chassis. (c) Dial cord rubbing against parts in chassis. (d) Tuning condenser bearing too stiff. Precautionary Lead Dress. - 1. All filament (brown) and B+ (red) leads must be dressed away from unshielded I.F. coil. 2. Green grid lead of 1A7G tube to be twisted around antenna (blue) lead for

12、capacity coupling. 3. Red and brown battery cable leads to be dressed and held against front apron with tape. BREAKAGE: Breakage of dial cord may be caused by any one of the following or a com- bination thereof: (a) The machined surface at the drive pulley being rough. (b) Surface of guide rivets be

13、ing trough. (e) Dial cord rubbing against head of guide pin rivets due to poor alignment between rivets and dial cord drum. (d) Guide pin rivets should be flush with mounting plate and tightly riveted at right angle to the plate, so as to avoid the possi- bility of a crack between rivet shoulder and

14、 dial plate, permitting dial cord to enter ami resulting in a premature failure of cord. A revised replacement shaft Stock No. 34124 is available for correcting slippage. Pull out tuning shaft after first removing the slotted spring washer used for folding tuning shaft in place. Insert replacement s

15、haft and lock in place with spring washer after first having ap- plied a drop of oil to the shaft bearing. Install new dial cord, placing 31 turns around the tuning shalt pulley REPLACEMENT SHAFT t7:=7.cce ORIGINAL SHAFT Replacement Dial, Pulley, and Shaft: A complete Dial Assembly (Stock No. 38781)

16、 consisting of dial plate, dial scale, pul- leys, drive drum, drive cord and spring, shaft, lamp bracket, and terminal strip is available for replacement on the Model BT -42 receiver. IIowever, the original assembly may be brought up to date by replacing the studs and shalt as follows: File off the

17、two old studs on the dial plate. lin, with solder, the surface (between dial and plate) around the stud holes, and insert the new pulley studs with the heads against the plate. Solder the studs so their heads are flat against the plate and the shanks are at right angles to the plate. The pulleys can

18、 now he slipped over the studs with the bearing surface toward the plate. Apply a drop of oil on each stud. Thread the drive cord as shown in the ing. Stock No. Description 38781 Dial -assembly complete (New type, including Stock No. 38783 and 34124) 38783 Pulley (2 pulleys, 2 studs) 34124 Shaft (Sh

19、aft and spring washer) draw - unit List Price 2.50 .25 .35 MODEL BT -42 Replacement Loudspeaker Cones: Three types of loudspeakers have been em- ployed in Model BT -42. Replacement cones are identified and available as follows: Speaker Marking Cone Stock No. 84650-1 33458 84650-2 35483 84650-5 35127

20、 The speaker marked 84650-5 uses output transformer Stock No. 35128. RCA VICTOR DIVISION OF RADIO CORPORATION OF AMERICA, CAMDEN N. J., U. S. A. 收音机爱 好者资料库 RadioFans.CN BOTTOM VIFVI Oc T )pa e.00KETS RI / 220,Ooo- ANT. ADJ 1A7( IST DET NET DYNAMIC SPEAKER / . DPST SWITCH ON VOLUME CONTROL BATTERY CA

21、BLE PLUG YEL, -RED Ory BROWN VIEW LOOKING AT PRONGS Sfeps Connect the high side of test- oscillator to- Tune test-osc. to- Turn Radio Dial to- Adjust the fol- lowing for max, peak output- 1 1A7G 1st-Det. grid cap, in series with .01 mfd. 455 kc Quiet point at 550 kc End of Dial C8, C9, C10, C11 (1st

22、 and 2nd I -F transformers) 2 Antenna lead (blue) in series with 100 mmfd. 1,500 kc 1,500 kc C5 (oscillator) 3 600 kc 600 kc L1 (antenna)* 4 1,500 kc 1,500 kc C3 (antenna) * When adjusting Ll (antenna), trimmer C3 should be in a minimum rapacity position (unscrewed). Replacement Parts Insist on genu

23、ine factory -tested parts, which are readily identified and may be purchased horn authorized dealers. STOCK No. DESCRIPTION STOCK Nc. DESCRIPTION 13057 12720 30433 33584 32787 4839 33952 34126 32150 32573 34121 32634 34125 33453 34123 34256 34122 30550 3708 12412 13715 12264 13730 CHASSIS ASSEMBLY C

24、apacitor -60 mmfd (C6, C13) Capacitor -100 mmfd (C12) Capacitor -400 mmfd (C16) Capacitor-.005 mfd (C14, C17) Capacitor-.05 mfd (C7) Capacitor -0.1 mfd (C1, C19, C20) Capacitor -8 mfd (C18) Clip-Dial lamp clip Coil-Antenna coil Coil-Oscillator coil Condenser -2 gang variable tuning Cord-Indicator dr

25、ive cord Dial-Dial scale Drum-Indicator drive cord drum Indicator-Dial scale pointer Lamp-Blinker lamp Plate-Metal support plate and bushing for dial Plug -4 contact male plug for battery cable Resistor -620 ohms, I watt (R9) Resistor -47,000 ohms, 3 watt (R4) Resistor -68,000 ohms, watt (R2) Resist

26、or -220,000 ohms, watt (Rl) Resistor -1 megohm I watt (R7) 12679 13167 13601 34124 32595 32537 31615 33296 34118 34119 34120 33458 33459 34127 31659 33312 31646 Resistor -2.2 megohm watt (R8) Resistor -3.9 megohm watt (R10, R11) . , Resistor -10. megohm I watt (R3, R6) Shaft-Tuning knob shaft Shield

27、-Tube shield Socket-Tube socket Spring-Drive cord tension spring Spring-Retaining spring for drum Transformer-First I -F transformer Transformer-Second I -F transformer Volume Control and switch SPEAKER ASSEMBLY 84650-1 Cone-Speaker cone and voice coil Transformer-Output_ transformer MISCELLANEOUS ASSEMBLY Escutcheon-Dial escutcheon Knob-Tuning or volume control knob Nut-Speed nut for tuning condenser support plate Spring-Retaining spring for knob 收音机爱 好者资料库 RadioFans.CN