Philco-Radio-and-Television-Corp-RT-300 电路原理图.pdf

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1、VOLUME R-20, MOST-OFTEN-NEEDED 1960 RADIO SERVICING INFORMATION PHILCO AM/FM TUNERMODEL RT-300 (Continued on page 110, over) This tuner is equipped with a front panel and mounting board and is intended for quick installation in the space pro vided in the H” line Philco Hi-Fidelity Phonographs* AM AL

2、IGNMENT PROCEDURE The AM alignment should be completed before the FM alignment is performed. Before beginning the alignment, allow the receiver and test equipment to warm up for fifteen minutes. Djal PointerWith the gang fully closed, adjust the pointer to coincide with the first small index mark to

3、 the left of the 54 (540 kc) on the scale. Tuner ControlsSet the function switch to the AM position and the AM tuning control as indicated. Output IndicatorConnect a scope to output jack, Jl. Signal GeneratorUse an AM r-f signal generator with 30% modulation. 1. Connect generator, through a .05 A*fd

4、 condenser, to the signal grid, pin 7 of the AM converter, S6 (6BE6). Con nect the ground lead to chassis. 2. Set generator to 455 kc. Fully open tuning gang. Ad just, in order given, top of T7 bottom of T6, bottom of T7, and top of T6 for maximum output. Repeat until no further gain is indicated. 3

5、- Connect generator to radiating loop. Set generator to 1600 kc. Set receiver to 1600 kc as indicated by pointer Adjust VC6A (osc. trimmer) for maximum output. 4. Set generator to 1400 kc. Tune receiver to signal and adjust VC5A (antenna trimmer) for maximum output. FM ALIGNMENT PROCEDURE The AM ali

6、gnment should be completed before the FM alignment is performed. 1. With the gang fully closed, adjust the pointer to coincide with the first small index mark to the left of the 88” (88 me) on the scale. 2. Set the function switch to the FM position and the FM tuning control as indicated. 3- Connect

7、 an oscilloscope, through a 100,000 ohm isolat ing resistor, to junction of R8 and C20. Connect the oscilloscope ground lead to the chassis. 4. Connect the signal generator to the cathode of the FM, RF amplifier, pin 8 of Si. Connect the ground lead to the chassis. 5. Inject a 10.7 MC marker signal

8、and a 10.7 MC sweep signal, approximately 150 KC total deviation (do not over sweep). Adjust cores in top and bottom of T3, T2 and T1 for maximum-amplitude, symmetrical curve with the 10.7 MC marker at the top of the curve. Adjust input signal to maintain output, as indicated on scope, below 2 volts

9、 peak during alignment. Repeat this step until no further gain is obtained. 6. Change scope connections to the output connector Jl. Inject a 10.7 MC, 30% AM modulated signal to the grid of the 6AU6, pin 1 of S4. Adjust top of T4 for minimum indication between peaks. Inject 10.7 MC sweep signal, appr

10、oximately 150 KC total deviation, to pin 1 of S4 and adjust bottom of T4 for maximum- amplitude, symmetrical output. Adjust input signal to maintain output, as indicated on scope, below 5 volts peak during alignment. (See NOTE below.) 7. Open tuning capacitor. Insert a 6-mil, non-metallic shim betwe

11、en stator and rotor of the FM gang and then close the capacitor against the shim. Inject 108.5 MC sweep signal (approx. 150 KC total deviation), through an antenna matching network, to the receiver antenna terminals. Adjust VC3 for maximum output. 8. Close (mesh) the tuning capacitor. Inject 87.75 M

12、C sweep signal (approx. 150 KC total deviation) through an antenna matching network, to the receiver antenna terminals, and adjust X3 for maximum output (see NOTE below). 9. Set pointer to 91 MC and inject a 91 MC sweep signal. Adjust X2 for maximum output. (See NOTE below). 10. VC4 is the oscillato

13、r bridge capacitor used to minimize oscillator radiation. This is a factory adjustment and should not require further adjustment in the field. NOTI: The signal input must be as low as possible in erder to obtain a sharp indication. In some cases it may be necessary to set the signal generator to the

14、 first sub harmonic. FM LIMITER 3RD FM IF IF AMP T1 1ST FMIF FM OSC FM OSC BRIDGE FM OSC FM ANT FM RF 109 Top ViewShowing Alignment Points, Tube Locations, Tie Lugs and Components 收音机爱 好者资料库 RadioFans.CN VOLUME R-20, MOST-OFTEN-NEEDED 1960 RADIO SERVICING INFORMATION PHILCO MODEL RT-300 _,u ,sr C-I!

15、j ,gUf Ms. IL14 (Continued) _-I *gvl q,I iNjIOZ:; I I55711 * I Wlif X MICA I, 10% -IC7= :t0 i VC3 , IS UUf | 5 / -3 3 UUf / ! VC2 Si / -J r r2 7 n / Uuf / -005 uf _u_ CI3* -*-f too uuf JAM, j 95V -It 1.2V 2 |MEG R2? STANDARD WIRING s i in ps *220 R6 2.211 J/ Jc20 R0 ,rl“7 77 17 UUf rpciz+A JM Ei5! s

16、: kl L 6V LAMPS /TI1 .XI - ,r. xi_ UTS 1 L V 22 1RI0 C23 -J50MF a c BQ EW NOTES 4- VOLTAGES MEASURED WITH A VTVM AT l|7V, 60U LINE UNDER NO SIGNAL CONDITION * INDICATES VOLTAGES READ IN EM . INDICATES A RESISTANCE OF LESS THAN 1A. COIL RESISTANCES READ WITH COIL IN CIRCUIT SWITCH POSITIONS CCW AM, C

17、WFM. POINTERS 28-9739-11 CORD V *55 1/4* SPRING 28-9490 CORD A or A EN0 2 f END1 - /M 1 SPRINGS- 9 56-2617 1.4s 9-1 SW1 REAR VIEW, IN AM POSITION (CCWI. CORD B -*14 19/32 10 7/32 ENOl NOTE* ILLUSTRATED WITH BOTH GANGS CLOSED. CORDIT 3 1/2 TURNS 110 Drive Cord Installation Details 收音机爱 好者资料库 RadioFans.CN