General-Electric-Co-218H 电路原理图.pdf

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1、收音机爱 好者资料库 RadioFans.CN MANUAL OF I9S0 MOST-OFTEN-NEEDED RADIO DIAGRAMS GENERAL ELECTRIC MODEL 218 ALIGNMENT EQUIPMENT NECESSARY FOR METER ALIGNMENT 1. Signal generator G-E YGS-3, or equivalent. 2. 20,000 ohm-per-volt meter. 3. Output meter. 4. .01 mfd. capacitor. 5. Four-turn, six-inch diameter loo

2、p of bell wire for AM, r-f and oscillator alignment. 6. Isolation transformer. NOTES FOR MBTER ALIGNMENT 1. Connect a 20,000 ohm-per-volt meter from junction of C29 and R18 to chassis. Use a ten-volt scale for steps 3, 4 and 5. 2. Connect a 20,000 ohm-per-volt meter from the grid of the limiter (pin

3、 1 of V4) to cathode of limiter (pins 2 or 7 of V4) in series with a 200,000-ohm resistor. The resistor must be con nected directly to the grid pin to minimize capacity loading and to isolate the i-f signal voltage from the meter. Keep signal gen erator down so that the meter does not indicate more

4、than one volt at the grid (5 microamps through 200,000 ohms). 3. Connect a standard output meter across the speaker voice coil. Turn volume control full on. Keep signal generator output low so that output meter indicates not more than Y2 watt during alignment. 4. Align the AM oscillator trimmer (Cl3

5、) and the AM r-f trimmer (C9) by coupling the signal to the loop antenna induc tively. Connect a four-turn, six-inch diameter loop of bell wire across the signal generator output terminals, and locate the loop about one foot from the radio loop antenna. The position of the loop in respect to the rad

6、io loop antenna should not be changed during any one set of adjustments to prevent possible errors in the peak readings. 5. Disconnect the copper strap from the band switch to pin 7 of the 12BE6 to align the 1st FM i-f transformer. Unsolder the strap from the tube pin connection. Resolder the strap

7、after Tl is aligned to 10.7 me as in step 8. 6. The AM r-f alignment should be made before the FM r-f alignment. With the gang condenser fully closed, the pointer should point to the dot on the dial scale after the letters “FM” on the left end of the dial scale. 7. The termination impedance of the s

8、ignal generator should be 300 ohms for FM r-f alignment. MODEL 218 H VERSION It is the same as the Model 218 except that the local oscillator is designed to operate on the high side of the incoming signal on FM reception. This change reduces the possibility of local oscillator radiation interfering

9、with television reception. METER ALIGNMENT CHART Step Signal ; Generator Frequency Signal Input Point Band Switch Setting 1 Dial Setting Adjust See Note AM I-F ALIGNMENT 1 455 kc Secondary and primary slugs of T5 for maxi- modulated 12BE6 grid (pin AM 550 kc mum. 3 2 with 400 7 of V2) thru Secondary

10、 and primary slugs of T2 for maxi- cps .01 mfd. i mum. FM DISCRIMINATOR AND I-F ALIGNMENT 3 10.7 un modulated Adjust T6 secondary for zero. Apply 1 volt signal input. 4 See adjust col. 12BA6 grid (pin 1 of V3) thru FM Detune signal generator to point of maximum meter reading. 1 5 Same freq. as in st

11、ep 4 0.1 mfd. Adjust T6 primary for maximum meter read ing. 6 _ Adjust slug of T4 for maximum. 7 10.7 me 12BA6 grid (pin 1 of VI) thru .01 mfd. Adjust secondary and primary slugs of T3 for maximum. 2 8 unmodu lated 12BE6 grid (pin 7 of V2) thru .01 mfd. and 4700 ohms. See note 5. Adjust secondary an

12、d primary slugs of Tl for maximum. 2.5 AM R-F ALIGNMENT 9 1500 kc Inductively coupled. See note 4. Adjust C13 for maximum. 10 AM mod ulated with 400 cps AM ; 1500 kc Adjust C9 for maximum while rocking dial. 3, 4, 6. FM R-F ALIGNMENT 108 me un modulated 98 me un modulated Dipole terminals 108 me Adjust 08 for maximum. 11 12 FM For max. output Adjust Cll for maximum while rocking dial. 2, 6, 7. 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 RadioFans.CN