RCA-Victor-Co-Inc-68R4 电路原理图.pdf

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1、MANUAL OF 1948 MOST-OFTEN-NEEDED RADIO DIAGRAMS FM I.F. R.F.AIignment* Range Switch in FM Position rca Victor nr=im- IVV/i* mr A A M w* Connect the the Tune Radio n IJA Dr_AAfl hiah tide of around teat- dial T Chassis No. RC-608 MODELS 68R1, 68R2, 68R3, 68R4 Circuit diagram next page. Tube and Trimm

2、er Locations Top View) FM Ratio Detector Alignment Range Switch in FM Position Same as in Step 2. Same aa in Step 2. Approx. .25 Volt output T6 top core for min. audio output.! 5 Reconnect VottOhmyst as in Step 1, omitting 680 ohm resistor. 6 Repeat Step 2._-_ 7 Remove ALL connections. 1 Approximate

3、ly 14.5 volts. tNear the correct core position the aero point is approached rapidly an continued adjustment causes the indicated polarity to reverse. Aslow approach to the zero point is an indication of severe detuning, and the bottom core should be turned in the opposite direction. IThe zero d-c ba

4、lance and the minimum a-f outputshould oocuratthe same 1 point. If such is not the case, the two cores should be adjusted occur with no further adjustment of either core. It may be advantageous to adjust both cores simultaneously, watching the VoltOhmyst. and the output meter, hooked across the voic

5、e coil, for the poult at which both zero d-c and minimum a-f output occur. Note*_Two or more points may be fouud which will satisfy the condition reauired in Step 4. T6 top core should be correctly adjuster when approxi mately M inch of threads extend above the can, therefore, esrcable to .tart adiu

6、stment with the top core In its furthest in _ position and turn out, while adjusting the bottom core, uutil the first point of minimum a-f and zero d-c is reached. 146 Connect Connect the the high aide of ground the teat- side of osc. to the test- Connect the d-c probe of a VoltOhmyst to the negativ

7、e lead of the 5 mfd. electrolytic condenser, 08, and the common lead of the meter to chassis ground. 10.7 me. tT3, bottom core 30% Maximum for maximum d-c mod. at capacity, across C 18. Load 400 (Fully the plate winding of cycles, meshed) T3 with a 680 ohm (AM) resistor.! To one terminal of the FM a

8、ntenna in series with .01 mfd. Same as 2. ? T3, top core for maximum d-c across C 18. Load the grid winding of T3 with the 680 ohm resistor used in Step 2. Same as 2. Tl, bottom core for maximum d-c across C 18. Load the plate winding of Tl with the 680 ohm resistor. Same as 2. Tl, top core for maxi

9、mum d-c across C 18. Load the grid winding of Tl with the 680 ohm resistor. To the To one other terminal of terminal the FM of the antenna in antenna series with in series a 120 ohm with a resistor. 120 ohm resistor. 106 me. 106 mc.$ Condensers C33 and C31 for maximum d-c output across Cl8. Same Sam

10、e 90 me. 90 me. Coils L2 and L3 for maximum d-c output across C18. Repeat steps 6 A 7 until further adjustment no longer improves calibration. Correct alignment of the 455 kc. I.F. requires that the 10.7 me. FM I.F. be aligned previously. tThis method is known as alternate loading which involves the

11、 use of a 680 ohm resistor to load the plate winding while the grid winding of the same transformer is peaked. Then the grid winding is loaded with the resistor while the plate winding is peaked. tWhen the windings are loaded it may be necessary to increase the 10.7 me input since the gain will decr

12、ease resulting in a small or no reading across C18. This reading should be maintained at 2-4 volts, by adjusting the input, as each transformer is aligned. Completely mesh the gang and see that the pointer goes to mechanical maximum calibration point at low end of band. (Reference mark on dial back

13、plate). “A” Band Alignment* Range Switch ia BC Position Connect the high side of the test osc. to Tune Turn the test osc. radio dinl to to Adjust for max. peak output. AM converter grid, pin 1, 6BE6 ia series with .01 mfd. “A” Band 455 kc. Quiet point at high freq. end. tT4Top core T4Bottom core T2B

14、ottom core T2Top core Antenna lead in series with 200 mmf. 1400 kc. “A” Band 1400 kc calibration pt 600 kc. A” Band 600 kc calibration pt. C37Osc. C34Ant. (Loop) L7Osc. Rock in. Repeat steps 3 and 4 until aligned When chassis Is installed, readjust C34 on the loop for max. output at 1400 kc. Dial-In

15、dicator and Drive Mechanism Correct alignment of the 455 kc. I.F. requires that the 10.7 me. FM I.F. be aligned previously. tAlign T4 and T2 by means of alternate loading. Use a 47,000 ohm resistor instead of a 680 ohm resistor. Alternate loading is explained in FM l.F.-R.F. Alignment._ 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 RadioFans.CN