GE-801-Rider-TV1电路原理图.pdf

TV PAGE 1-28 GE MODEL 801 Early, Late GENERAL ELECTRIC CO. ELECTRICAL RATING: Frequency Voltage Wattage ( Radio I Wattage (Television! 50 60 cps 105 125 v. 85 215 60 cps 105 125 v. 85 215 R-F FREQUENCY RANGE: Selector Switch Position Radio No. 1 No. 2 No. 3 . 4 . 5 . No. No. No. 6 . . . No. 7 . . . No. 8 . No. 9 . No. 10 . No. 11 . . No. 12 . No. 13 . Freq. Range .540 1600 kc . 44 - 50 me 60 me 66 me 72 me 82 me 88 me 180 me 186 me 192 me 198 me 204 me 210 me 216 me Picture Carrier 54- . 60 . 66 . 76 . 82- .174- .180- . 186- 192 - .198- .204 .210 45.25 55.25 61.25 67.25 77.25 83.25 175.25 181.25 187.25 193.25 199.25 205.25 211.25 INTERMEDIATE FREQUENCIES: Television Video (carrier freq. equivalent). . . Television Audio Radio AUDIO POWER OUTPUT: Undistorted Maximum P/CTURE SIZE: Height Width ANTENNA REQUIREMENTS: Type Impedance Sound Carrier 49.75 59.75 65.75 71.75 81.75 87.75 179.75 185.75 191.75 197.75 203.75 209.75 215.75 . 26.4 me 21.9 me . 455 kc 3 watts .4.5 watts . 6 inches . 8 inches .Folded Dipole 300 ohms TUBES: (24 Including rectifiers) Symbol Purpose (V 1) Television R-F Amplifier (V 2) Television Converter-Oscillator . (V 3) 1st Video I-F Amplifier (V 4) 2nd Video I-F Amplifier (V 5) 3rd Video I-F Amplifier (V 6) Video DetectorBias Rectifier . . . (V 7) Video Amplifier (V 8) Picture Tube (V 9) Clipper-Horizontal Sync. Ampli 6SN7GT (V10) Horizontal Discr.D-C Amplifier 6SL7GT (Vll) Horizontal Multivibrator (V12) Horizontal Output (V13) High Voltage Rectifier (V14) Horizontal Damping (V15) Horiz. Discrim.Vert. Sync. Amplifier (V16) Vertical Multivibrator (VI7) Vertical Output (V18) Radio Converter (V19) 1st Audio I-F Amplifier (V20) 2nd Audio I-F Amplifier (V21) Audio Discrim.Audio Amplifier (V22) Audio Output (V23) Low Voltage Rectifier (V24) Low Voltage Rectifier * Changed to a Type 5Y3GT in late production receivers, at approximately serial No. 2000. Type 6AU6 7F8 6AC7 6AC7 6AC7 6H6 6AC7 10BP4 6SN7GT 807 8016 6AS7G 6SL7GT 6SN7GT 6V6GT 6SA7 6SG7 6SV7 6AQ7GT 6V6GT 5V4G* 5U4G Model 801 LATE PRODUCTION The Model 801 receivers above Serial No. 550 (approximate) are known as late pro- duction receivers. These receivers differ electrically from the early production re- ceivers, as follows; (NOTE - Some early production receivers below Serial No. 550 may incorporate some of these changes.) (1) Tube V12 changed from a Type 807 to a Type 6BG6G. This Improved the horizontal size at low line voltage conditions. The 6BG6G tube is very similar to the Type 807 except for the basing. (2) The r-f head-end unit was changed to provide better detail, as follows: The r-f coils were more heavily loaded by reducing the r-f plate resistor. The converter grid coils on Channels #3 through #5 were loaded with resistance. A 10 mmf. capacitor, C110, was connected from converter plate to ground in conjunction with 1st i-f trans- former change to permit better frequency characteristics after alignment of head-end unit. The heavier loading of r-f and converter coils reduces the available sensitivity somewhat. ( . 3 ) The 1st video i-f transformer, Tl, was changed so that the primary is induc- tively tuned instead of by capacity, as in the early production. This permits the con- verter grid circuit to work at a higher input impedance which is not affected by plate tuning, as in early production transformer. The 27.9* me wave trap also changes from an absorption shunt trap, to a series tuned trap in the late production transformer. (4-) The video amplifier tube (V?) plate chokes L3 and L4- were increased in value to improve detail. John F. Rider RadioFans.CN GE TV PAGE 1-29. GENERAL ELECTRIC CO. MODEL 801 VIDEO AMPLI AUDIO I-F AUDIO DETECTOR - OUTPUT ;, 1. Block Diagram 3. 4. 5. 6. 7. 8. 9. DESCRIPTIONTELEVISION CIRCUITS The television receiver circuits are divided into the follow- ing sections:, 1. R-f amplifier, converter and oscillator 2. Video and audio i-f amplifier Video detector and amplifier Sync pulse clipper-amplifier Horizontal multivibrator and AFC sync. Horizontal sweep output Vertical multivibrator and sweep output High voltage power supply (H.V. supply) Low voltage power supply (L.V. supply) A brief description of the operation of each section is de- scribed in the following paragraphs. This is supplemented by a comprehensive television training course in the publica- tion, RSM-4-TV. A block diagram of the complete receiver is shown in Figure 1 to assist in signal tracing and to better visualize the operation of the receiver as a whole. I. R-F AMPLIflCR, CONVERTER A OSCILLATOR ($ figun 2) The r-f amplifier makes use of a Type 6AU6 tube connected as a triode grounded-grid amplifier. The antenna is connected into the cathode circuit so as to provide a substantially constant input impedance of 300 ohms to the antenna at all frequencies. With a 300-ohm antenna and transmission line system, this coupling arrangement permits optimum transfer of signal from antenna to r-f amplifier for all 13 channels. R101 is the normal bias resistor. A choke, LK, is placed in series with this cathode resistor to prevent the input im- pedance from being lowered by the shunting effect of the total stray capacity to ground of the cathode of the tube. The choke value is changed with frequency. The r-f amplifier is coupled to the converter tube by a wide band transformer consisting of windings Lp and L. R F ,., ,-ir.A CONV. CI03CI04 VIDEO I-F AMPLI. INDICATES SWITCHING POINT The windings are self-tuned by the distributed and tube capacities to provide optimum gain. On channels No. 1 and No. 2 the transformer is triple tuned to prevent the image frequencies of the 88-108 me FM band frm interfering with these two channels. The triode converter is one section of a Type 7F8 dual triode, V2A. Bias for this tube is provided by the oscillator voltage appearing in the grid of V2A causing grid rectification charging the grid resistor- condenser combination, R104 and C104. The oscillator makes use of the remaining half of the Type 7F8 tube, V2B, and is inductively coupled to the converter grid by locating the oscillator grid coil, T22, on the same coil form as the converter grid coil, L. The oscillator is a modified Colpits oscillator, oscillation being produced by the cathode-to-grid, Cg, and cathode-to-plate, Ck, interelectrode capacities of the oscillator tube. The choke Lf provides a d-c ground to the cathode of the oscillator but maintains the cathode off-ground at the r-f-frequencies. The oscillator operates on the high frequency side of the r-f signal on all bands. The r-f amplifier, converter and oscillator is constructed as a complete unit sub-assembly which can readily be de- mounted from the main chassis. 7. VIDEO AND AUDIO I-F AMPLIFIERS (S Flgun 3)The video i-f amplifier makes use of a three-stage band-pass amplifier using three Type 6AC7 tubes. The transformers, Tl, T2, T3, and T4, are overcoupled and then loaded with resistance, RL, to give an adequate (approx. 4 me) band-pass frequency characteristic. A third winding is added to each video transformer and tuned to trap out the adjacent audio and associated audio interference. The trap on Tl is tuned to 27.9 me to provide rejection of the adjacent channel audio i-f, while the traps at T2, T3, and T4 are tuned to 21.9 me to provide rejection of the same channel audio. Tl Fig. 2. I-f AmplHUr, Converter * Oidllator Fig. 21.9 MC 3. Vld.o A Audio I-f Amplifier John F. Rider RadioFans.CN TV PAGE 1-30 GE MODEL 801 GENERAL ELECTRIC CO. me audio i-f frequency is developed by taking the 21.9 me signal from across the trap on T2 and applying it to the grid of the audio i-f amplifier tube V19. The ground return side of the trap is effectively connected to ground at 21.9 me through the low impedance circuit offered by the capacitors C74 and C42. Since the audio channel of the television is frequency-modulated, the transformer T6 functions with the diode sections of V21 as the discriminator. Bias voltage, derivedby rectifying 6.3 volts a-c through the diode V6B, is applied to the grid circuits of the video i-f amplifier tubes, V3 and V4. A variable potentiometer con- trast control, permits this voltage to be changed so as to vary the gain of the i-f amplifier. 3. VIDEO DETECTOR AND AMPLIFIER (See figure 4)The video i-f amplifier output is applied to a diode rectifier, V6, and the diode load, R14, is connected so as to develop a negative- going signal voltage at this point. The signal is amplified by tube V7 and then applied directly to the cathode of the pic- ture tube, V8. This provides direct coupling so that d-c re- insertion is unnecessary. The chokes L5 and L3 are series peaking chokes, while L4 is a shunt peaking choke. These are used to obtain good high frequency response. L5 also pre- vents harmonics of the i-f frequency from being passed through the video amplifier. R16 is the V7 tube plate load resistor. T4 V8 Fig. 4. Video Detector the response curve on the scope should increase in size proportionally. Set Contrast Control to half-advanced position. The response curve of the amplifier at the grid return of V20 should appear as in Figure 8A. For discriminator alignment the secondary trimmer, C78, of T6 is aligned by using a tone modulated 21.9 me signal and listening to the tone at the loudspeaker. The trimmer is adjusted for minimum tone signal output. I-f the sweep is used for the secondary trimmer alignment, the cross-over should be symmetrical about a 21.9 me marker and should be a straight line between the alternate peaks, as shown in Figure 8B. Reconnect oscilloscope across the top of the volume control. Fig. 8. T-V Audio I-F Curves 21 9 MC MARKER John F. Rider For test patterns see back of Manual RadioFans.CN TV PAGE 1-32 GE MOL/l, 801 GENERAL ELECTRIC CO. 2S4M.C 23 CMC 23 0 M.C Fig. 9. Video I-F Alignment Curves ,-2MC. 25.65M.Q. 26.4 M.C. With the same sweep input as in step 1, adjust the primary trimmer, C84, of T6 for maximum peak-to-peak amplitude of the positive and negative peaks as shown in Figure 8B. 5. Video I-F AlignmentThe video i-f amplifier uses trans- formers which are coupled and loaded to give the proper band-pass characteristic. Before attempting alignment of the video i-f, the sound i-f traps should be aligned as in ( 3 i , then do not touch these trimmers when making the video i-f alignment. Stage-by-stage alignment should be performed so as to duplicate the curves, as shown in Figures 9A, B, C, and D. The markers are used to establish the correct bandwidth and frequency limits. The trap formed by L20 and C89 in the cathode of V4 is used to reduce the overshoot of the 21.9 me traps. Adjust the spacing of turns comprising L20 by either pushing them to- gether or separating them so as to give a minimum amplitude to the overshoot. Connect the sweep generator to the tube grid preceding the transformer to be aligned. Adjust the sweep width for a minimum of 10 me about the. center frequency of the video i-f. The marker frequencies are supplied by a signal generator and sufficient marker signal may be supplied in most cases by merely connecting the high side of the signal generator to the television chassis. The primary of the transformer preceding the grid where the signal is applied will act as a trap putting a hole in the alignment curves as viewed on the scope unless it is short circuited or detuned. It may be detuned readily by connect- ing a 100 to 200 mmf capacitor across the primary trimmer or place a temporary short circuit across the primary trimmer. Be sure to remove this capacitor after the stage is aligned. Keep the input of the sweep generator low so as not to overload the video i-f amplifier. The response curves shown are obtained on an oscilloscope at the junction of L4 and R16. Use a 10,000 resistor in series with the input lead to the oscilloscope. The contrast control should be advanced approximately to its half-advanced position. The Selector Switch should-be turned to radio position and a temporary jumper put across filament switch wafer so as to keep the television tube filaments lit while in this radio position. If a television position is used, the i-f curve will be affected by the interaction from the r-f coil in the converter tube grid. NOTE When jumper is used, remove B+ from r-f assembly by disconnecting external lead to terminal ( 2 ) of r-f assembly, see Fig. 12. 6. Oscillator Adjustment-The oscillator coil must be ad- justed so that the Television Tuning Condenser, C112, will tune the sound carrier of the television signal at the middle of its range. Set the condenser, C112, to mid-position. Then adjust oscillator coil for channels No. 1 through No. 6 by spreading turns to raise frequency or compressing turns to lower frequency. For channels No. 7 through No. 13, the oscillator coil consists of a single turn. Adjust these coils by spreading the gap to lower frequency or closing the gap to raise frequency in the leads of the coil which run to the terminals. Apply the signal generator with tone, modulation to the antenna input terminals and set the generator to the sound carrier frequency for the channel under alignment. The signal generator must be very accurately calibrated. This can be done by beating its output against a known channel carrier or use a station operating on the channel and tune in the sound. For output indication, advance the volume control about to mid-position so that the tone modulation or audio modula- tion on the channel station may be heard through the loud- speaker. The oscillator coil is located on the coil form or assembly nearest to the front of the switch assembly and is wound of heavier wire than the other coils. This is shown in Figure 10. 7. R-F Coil AlignmentThe r-f coil assembly is designed for stable, band-pass operation and under normal conditions will seldom require adjustment. In cases where it is definitely known that alignment is necessary (such as when the present coil is damaged and has been changed), do not attempt the adjustment unless suitable equipment is available. When tubes VI or V2 are changed, alignment of r-f and oscillator may be necessary. The minimum requirements for correct r-f alignment is to provide the correct band width, and for the response curve to be centered within the limit frequencies shown for each of the individual bands, as shown in Figure 11. It is also necessary that the curve be adjusted for maximum amplitude consistent with correct band width. To provide these mini- mum requirements, the r-f coils are overcoupled in a very similar manner to the video i-f transformers. However, instead of adjusting capacity to tune the coils, the inductance is varied by moving a few turns. Coupling is also adjustable by moving the entire coil either away from or toward the adjacent coil on the form. The physical assembly of the coils in the band switch locates the r-f amplifier plate coil at the rear of the switch and the oscillator coil towards the front end. Two types