Fault Insertion: Remove the shorting shunt from pin 1 & 2 and place it between 2 &
3 of jumper J42
Symptoms: Picture & sound OK but not getting OSD.
Fault Section: System control Section.
Procedure:
• Check the vertical Blanking pulse at TP46 ,if it is OK then
• Check the Horizontal Blanking pulse at TP45, if it is not present then
• The components are faulty and no continuity of track for horizontal blanking pulses.
• Remove the shorting shunt between 2 & 3connect it between 1 & 2 of jumper J42
Result: Now there should be OSD.
Experiment 24 Objective:
Study of detail circuit description of Switched Mode Power Supply (SMPS) section The trainer has SMPS Power Supply. It outputs are +110V and +22V mainly. AC mains supply is fed to input of line filter L1210 through ‘On-Off’ switch. The main function of line filter is to prevent the spikes present in 50 Hz AC supply for the purpose of safety of trainer kit. Output of line filter is connected with degaussing coil through PTC R802 is connected around the picture tube. When switching ON the TV trainer the degaussing coil gets the supply and demagnetize the picture tube. Bridge rectifier (D806, D807, D808, D809 all are IN4007) is connected with output of line filter. A filter capacitor C815 (100µf. 450V) is connected between positive and negative terminal of bridge which rectifies the DC properly. Negative end of bridge is connected with ground by a resistance R805 (2.2Ω/1W) is called floating ground.
This floating ground is connected with main chassis ground by a resistance R829 (10M/0.5W). There is 150 VDC on floating ground with respect to main ground. In the same way there is approximately 300 VDC at positive point of bridge with respect to floating ground. Due to this there is 450 VDC voltage at positive of bridge with respect to chassis ground. So while testing SMPS section we have to always connect negative of multi-meter with floating ground and for testing of other circuits main ground is used.
Note: Never short floating ground with main chassis ground, it may damage the circuit.
The Power Supply section uses 4 transistors in the circuit Transistor Q801 (C1815) - Error Detector Transistor Q802 (2SA1015) - Error Driver - 1 Transistor Q803 (C1815Y) - Error Driver - 2 Transistor Q804 (BD508AF) - Switching Transistor
Q802 and Q803 are used to control the duty cycle of Q804. Both these transistors are working as complimentary transistors and get the required supply from pin no. 8 of SMPS transformer for functioning. According to output voltage at secondary of SMPS transformer Q801 is used to change the duty cycle. Zener diode D811 (8.2V) is
• Pin no. 1 of IC TDA2611 is connected with it by a resistance R601 (6.1Ω/1W).
• Input of IC102 (LM7805) is connected with it by, a resistance R980 (150Ω/1 W).
• Relay (+12V) gets this supply by a resistance R610 A (68Ω/1W).
• When we switch ON the power switch +22V supply is produced without using the power switch of remote. Pulses produced at pin no. 3 & 4 of SM transformer are connected with R610 (1Ω/1W) and R610 B (100K) R610B is grounded and other end is connected with N/O (Normally open end) of +12V relay. When we switch ON the power, relays pole is connected with no terminal and pulses are then rectified by D602 (BY159) and filtered by C810 A (100µf/160V) +110V output voltage is obtained. This +110V is used in other circuitry part in following manner.
• At +110V line a resistance, RA02 (15K) is, connected its other end is connected with DA13 (Z33V) zener diode. This +33V supply is filtered by CA04 (1µf/63V). It is used for TV terminal at tuner.
• +110V is supplied to primary of T401 of horizontal driver transformer by R416A (2K2).
• It is connected with pin no 3 of EHT transformer by a resistance R224 (1Ω/
1W).
• Horizontal hold resistance gets this supply by a resistance R451 (10K). Also base biasing is given to horizontal driver transistor Q402 by resistance R408 (1.8K), R411 (33Ω).
• Pin no. 33 of IC501 (CP7698) (Horizontal Oscillator Section) gets +110V supply by a resistance R416 (6K8 5W).
General Details for Servicing Set Dead, AC Fuse F1210 Blows ‘Off’:
Mains wire, ‘On-Off’ switch, C811 (100KpF), line filter LI 210, degaussing coil D806-D809 (4 x 1N4007) C811A-C812-C812A-C813-C813A (4 x 4K7pF) C815 (100MFd/400V), Q804 (BU508AF) & related parts, check entire power supply section.
Set Dead, No Output From Power Supply:
Mains wire, ‘On-Off’ switch, F1210 (3.15A), L1210, R826 (4.7Ω/10W), D806-D809 (4x 1N4007), C815 (100MFd/400V), R804-803 (220K), R816 (3.3Ω/2W), R805 (3.3Ω) 0804 (BU508AF), R815 (27Ω/2W), C808 (0.lMFd), D803A-D804 (BY159), C807 (100MFd), R824 (12Ω/1W), Q803 (C1815), Q802 (2SA1015), D803 (BY159), C806 (10MFd), Q801 (C1815) & related parts T801 (rare), check secondary side of T801 & check for Stand by.
Switching Transistor Q804 (BU508AF) Overheats or Blows ‘Off’:
Q804 (BU508AF) & its mica C810 (IKpF),C803 (1KpF),C815 (100MFd/400V), D606-O809 (1N4007), C807 (100MFd), 0804-D803A (BY159),C808 (0.lMFd),Q803 (C1815),Q802 (2SA1015),D802 (9.lV-zener) D801 (8.W-zener), D803 (BY159), C806 (10MFd),Q801 (C1815) & related parts,T801 (rare), check secondary side of T801, check horizontal output section.
No Variation m Power Supply Output:
VR801 (1K),R819 (3K3) R818 (6K8) 0803 (BY159), C806 (10MFd), R821 (1K8), R820 (8K2), D801 (8.lV-zener), Q801 (C1815), R822 (10K) R823 (6K8), D802 (9.1V-zener) C804 (330Ω),R811 (0.22MFd),Q802 (2SA1015) R826A (4K7) Q803 (C1815),R824 (12Ω/1W) R815 (27Ω), C808 (0.lMFd) D803A.D804 (BY159), C807 (100MFd) Q804 (BU506AF) & related parts.
Only +110V Supply is Missing From SNIPS:
Winding between pin no 3-4 of T801 is open or def R610 (1.2Ω/1W). Relay RL1 def.
or set is in Standby (check as given in fault of Standby), D602 (BY159), C610A (100MFd/160V) L601, R610B (120V-zener), check +110V supply line for short.
Only Low Voltage Supply is missing From SMPS:
Winding between pin no 2-4 of T801 is open or def D810 (BY159). C816 (1000MFd/35V) check low voltage supply line for short.
Picture (Raster) Shaking Horizontally:
Less AC mains, C815 (100MFd/400V), C610A (100MFd/160V), check bridge rectifier circuit, no variation in power supply output voltage or it is low.
Set is in standby i.e. No Power-ON:
Low voltage supply from SMPS is missing, R832A (270Ω), C943 (3.3MFd), IC102 (L7805), C942A & C942B (22 MFd), X10 (10 MHz), Q910 (BC558B), R973A (IK),
R973 (390Q), D911 (3.6V-zener), no output from pin no 42 of IC01 IC01 (CTV222S) def, R998 (IK) R1003 (2K2) R1004 (2K4), R1001 (10K) Q911A (BC547B), R1002 (100Ω), Q912 (BC547B) R610A (68Ω), C803A (100MFd) D811 (BY159), relay RL1 defective.
Reset Problem:
Many a times TV comes in Standby after switching it on by mains ‘On / Off’ switch due to falling the Reset voltage to zero. Therefore check Reset voltage & connected (BC558B) CA13 (2.2MFd), tuner IC01 (CTV222S-PRC1) defective.
Only UHF Band is Not Switching:
C921 (100pF) R934 (100K), Q905 (BC547B), R936 (10K), RA05 (22K), QA04 (BC558B), CA14 (10MFd), tuner,IC01 (CTV222S-PRC1) defective.
Tuning is not possible:
FT+/FT- keys def check key matrix circuit related with pin no 13 to 20 of IC01, no output from pin no 1 of IC01 IC01 (CTV222S-PRC1) def R908 (1K) C905 (100pF), R907 (5K6) C904 (100pF) R906 (1K5) Q901 (2N2222A), R904 (220Ω) R905 (33K) RA02 (12K/2W) DA13 (33V-zener) CA03 (10KpF) CA04 (lMFd/63V), R903 (15K) C902 (0.1MFd) R902 (10K) C952 (0.1MF), R901 (33K), C901 (0.1MFd), tuner def.
Auto Search is Not Possible or Indefinite, Auto-Search I.e. in Auto-Search Mode Tuning Does Not Stop When Any Station is Received:
AUTO key is def check key matrix circuit related with pin no. 13 to 20 of IC01 check IDENT at pin no. 34 of IC01, R34 (3K), C951 (820pF) C950 (1KpF) R979 (6K8),
(BY159), C806 (10MFd), D802 (9.1V-zener), R823 (6KB), P822 (10K), R821 (1KB), R820 (8K2) D801 (8.1V-zener) R818 (6K8) R819 (3K3), VR801 (1K) Q801 (C1815).T801 (rare) R6106 (120V-zener) check secondary side of T801.
No EHT, Power Supply OK:
R444 (1Ω/2W) L406,Q404 (BU508D),C463 (390pF) horizontal driver tralo T401,R416 (2K/3W), C416 (270pF), Q402 (C2229),R411 (33Ω) R408 (1KB) L407,C410 (1KBpF),R416A (6K8/2W) R30C (180Ω),DlA (1N4148) C409 (10KpF) C408 (10MFD/50V),C405 (0.003MFd) R406 (150K),R410 (15K),VR4S1 (10K) IC501 (DBL2003/TA7698AP)
No EHT, Power Supply Output Drops:
Q404 (BU5060) & its mica, C440 (0 0068MFd) C444 (560pF) horizontal deflection coil, C442 (0.47MFd) D406 (BY159) D408 (BY159) C821 (33MFd) check diodes &
capacitors related with EHT winding or + 110V supply line for short or leaky, EHT T461.
Horizontal Output Tr. O404 (BU508D) Overheats or Blows ‘Off’:
Excess output from power supply Q404 (BU508D) & its mica C440 (0.0068MFd), C444 (560pF), horizontal, deflection coil, C442 (0.47MFd) D408-O406 (BY159), C821 (33MFd), EHT T46V over oscillation in horizontal oscillator, check entire horizontal section & power supply section
Vertical Line, Sound Normal:
Horizontal deflection coil 01 its wire, C442 (0.47MFd), L411 Width Problem (Width Less or Excess):
Less or abnormal output from power supply C442 (0.47MFD/400V), L411 R455 (1K), horizontal deflection coil, C440 (00068MFd) C444 (560pF), Q404 (BU508D), D408-D406 (BY159), C821 (33MFd), EHT T461 check entire horizontal section.
Bright White Vertical Strip like Ringing at One Side of the Screen:
Check R455 (1K/1W) for open Color Patches on the Screen:
Strong magnetic field near picture tube, PTC R802, degaussing con, demagnetize the picture tube with the help of an external degaussing coil, picture tube defective.
Memory Problem:
Check + 5V at pin no 1&6 of IC104 R988 (100Ω). R988A (100Ω), R985 (3K3), R966 (3K3), R987 (10K), IC104 (PCF8582), IC01 (CTV222S-PRC1)
No Operation Through Remote Control Handset While Handset is OK & Front Panel Keyboard is Working Normally:
+5V supply to Remote Eye (Sensor) is missing. No output from Remote Eye Sensor) or it is defective R984 (47K), R983 (470K), R982 (1K), IC01 (CTV222S-PRC1) defective
No Operation through Front Panel Keyboard While Remote Control Operation Is OK:
Any key in the Front Panel Push Button Keyboard is faulty Keypad dusty or rusty, check key matrix circuit related with pin no 13 to 20 of IC01 R947 to R954 (1K x 8), C924 to C930 & C934 (100pF x 8), 0905-0906 (1N4148) check connection between Main Board & Front Panel Push Button Keyboard, crystal X10 (10 MHz) IC01 (CTV222S-PRC1) defective
Volume Up/Dn is Not Functioning:
VOL+/VOL- key def check key matrix circuit as given in above fault, no output from pin no 2 of IC01 IC CTV222S-PRC1 def R916 (1K) R915 (15K) R914 (470Ω) R913 (8K2), 0901 (1N4148) Q903 (BC547B) R912 (2K2) C907 (10MFd) R908A (68K) R910 (47K), R909 (22OK) R901 (220K), Q902 (BCS47B) C906 (47MFd) R614 (3K) C603A ,(1MF), IC DBL2002/TA7CTOAP (rare).
Brightness Up/Dn is Not Functioning:
Check MENU & VOL+VOL- keys, check key matrix circuit, no output from pin no 3 of IC01. IC01 (CTV222S-PRC1) del, R917 (IK) C909 (100RF) R916 (IK) C910 (0.01MFd) C911 (10MFd) R919 (39K) R920 (39K), C207 (22MFd), R212 (10K) R214 (1K5) R352 (5K) R209 (36K), IC DBL2003/TA7698AP (rare).
Contrast Up/Dn Is Not Functioning:
Check MENU & VOL+/VOL- keys, check key matrix circuit, no output from pin no 5 of ICOI IC CTV222S-PRC1 def R921 (1K3, C913 (100pF) R922 (100K) C915 (0.1MFd) IC103 (LM358N) & its supply, R923-R924 (100K) R925 (10K) R926 (1K), C919 (10MFd) R213 (68K), IC DBL2003/TA7696AP (rare).
Colour Up/Dn is Not Functioning:
Check MENU & VOL+/VOL- keys, check key matrix circuit, no output from pin no 4 of IC01, IC01 (CTV222S-PRCf) del R927 (1K) C942 (100pF) R928 (100K), C914 (0.1MFd) IC103 (LM358N) & its supply, R931-R929 (100K) R930 (10K) R932 (IK), C916 (10MFd) C506 (10KpF), R505 (27K), IC DBL2003/TA7698AP (rare)
EHT & Sound OK, No Light or Low Light or Dark Picture or Brightness Problem:
Adjust screen control, check CRT filament supply, R920 (1.8Ω), C901 (2K2pF).
check + 12V supply R448 (6.2Ω) D408 (BY159), C449A (1000MFd), L410, C446 (1000MF), C527 (10MF) C523 (47KpF) check Bright A Contrast control circuits at System Control section R203 (1K5), W201 R210 (1K5) C204 (0.47MF), R209 (36K) R212 (10K) R214 (1K5) R352 (5K) D241 (1N4148), D1 (BY159), D504 (1N4148), R241 (100K), C240 (2.2MFd) D242 (1N4007) R441 (1K) C445 (0.022MFD), R270 (100Ω) D244 (1N4148) R217 (330Ω) D243 (1N60), R242 (56Ω) R219 (220Ω) Q202 (A1015) check pin no 1 2 3 4 23 39 40, 41 and 42 of IC501 IC501 (DBL2003/TA7898AP) def CRT base loose or faulty, check CRT earthling, CRT del.
Retrace (White) Lines, Sound Normal:
Adjust screen control D406 (BY159), C447 (10MFd), Q202 (AT 015) & related parts IC DBL2003/TA7898AP A related parts, CRT base loose/faulty CRT defective.
Retrace Lines With Picture In Full Screen or Only at Top Portion. Sound Normal.
Screen control mistimed, R321 (1K) D310 (8.2V-zener) R326 (10K), D202-D203-D204 (1N4148), R217 (330Ω), Q202 (2SA1015) & related parts, also check as given in above fault.
Raster & Sound OK, No Picture or Weak Picture or Poor Contrast/Contrast Problem:
L105, R201 (330Ω) L201 & 2201 C210 (68pF), R204 (820Ω), C202 (150pF), R207 (330Ω), W201 R203 (1K5), R210 (1K5), C204 (0.47MF), R209 (36K) C445 (0.022MF) R441 (1K), C240 (2.2MF), D242 (1N4007) R241 (100K), D504 (1N4148) R240 (100K) check Contrast & Brightness Control circuits at System Control section.
Q202 (2SA1015) & related parts check pin no 1, 2 3 4 23, 39 40 41 & 42 of IC501 IC DBL2003/TA7698AP def, check Video IF & AGC.
Total Sync Loss, Sound Normal:
R301 (750Ω), R302 (560K), C301 (1MFd) D301 (1N4148), C302 (0.01MFd) R307 (56K) C3O3 (560pF), R303 (2M2), IC DBL2003/TA7698AP
Horizontal Rolling, Sound Normal:
Adjust & check VR451 (10K) R410 (15K), R406 (150K) C405 (0.003MFd), R405 (36K) R404 (3K3), C407 (1MFd), C406 (1MFd), C403 (5K6pF) R403 (3K3), C402 (0.47MFd), R402 (27K) R401 C401 (10KpF) ICDBL2003/TA7698AP.
Vertical Rolling, Sound Normal:
Adjust & check R351 (220K) R34A (220K), R308 (39K), C306 (0.22MFd) R330 (3K) C321 (0.033MFd) R305 (2K4) C305 (0.015MFd) R310 (10M) C310 (47MFd).
IC DBL2003/TA7698AP.
No Colour or Abnormal Colour, Black & White Picture & Sound Normal:
Antenna and its wire, balun/adapter, adjust the fine tuning R501 (820Ω), C501 (l5pF) L502,C502 (10pF), R504 (330K), C504 (1MFd) R505 (27K),C506 (10KpF) check (4,7MFd) R520 (1K2), R518-R519 (22K), R552 (5K) C519-C520 (0.022MFd) C319 (0.47MFd) R319 (2K7) D311 (BY159) R322 (1K), R329 (1K), R512 (100K),C524 (CTV222S-PRC1) def. check circuits related with pin no, 22, 23 24 & 25 of IC01.
Only Red Colour OSD is missing:
No output from pin no. 22 of IC01 IC CTV222S def R955 (1K), C931A (100pF).R2 (1000Ω).R3 (390Ω).T2 (C1815), R4 (220Ω) 4 related parts
Only Green Colour OSD is missing:
No output from pin no 23 of IC01 IC CTV222S def R956 (1K), C931B (100pF), R5 (100Ω), R6 (270Ω).T1 (C1815).R6 (220Ω) 4 related parts.
Only Blue Colour OSD is missing:
No output from pin no 24 of IC01, IC CTV222S def R957 (1K) C831 (100pF) R8 (100Ω) R9 (390Ω), T3 (C1815), R7 (220Ω) A related parts.
On-Screen-Display Blanking Problem:
No output from pin no 25 of IC01, IC01 (CTV222S-PRC1) def, R958 (1K), R999 (4K7), Q908 (BC547B), R960-R961 (680Ω).R956 (10K).C832 (100pF).Q909 (BC558B), R965 (330Ω) C933 (220pF).R963 (1K) R964 (330Ω), D910 (1N4148),
No Picture, No Sound, No Snow, Raster OK:
L106.C107 (100MFd),CA08 (220MFd),Q161 (C388A) & related pads, SAW-Filter Z101,L102.R101 (820Ω),C101 (10KpF),C102 (1KpF), R108 (3K9).L151,L105, check AGC,C601 (0.22MFd),R107 (820K),R151 (5K),R105 (330Ω),IC101 (DBL2002/TA7680AP), tuner defective.
No Picture, No Sound, Only Snow or Picture With Snow:
Antenna & its wire, ballun/adaptor, adjust fine tuning, check Band Switching &
Tuning Voltage circuits, +12V to tuner MB is missing.L161,R161 (100Ω),C161 -(10KpF);R162 (1K),R163 (5K6),R164 (220Ω).C162 (10KpF).L162,R165 (470Ω), R166 (33Ω),Q161 (C388A),C163 (10KpF),Z101,L102,R101 (820Ω),C101 (10KpF),C102 (1KpF),L151,C601 (0.22MFd),R107 (820K),R151 (5K),C103-C104 (10KpF),R105 (330Ω),R104 (68K).R106 (100K),CA09-CA10 (4.7MFd),IC DBL2003/TA7680AP, tuner defective.
Tuning Drifts Automatically/AFT Problem:
L152,C174 (15pF),C175-C176 (2.2pF),C172 (1KpF),IC DBL2002/TA7680AP,C178 (1KpF),R171 (1K2),C171 (10KpF),R1 (100K),R2 (56K),R3 (47K),tuner.
Horizontal Line, Sound Normal:
R327 (10Ω),D302 (BY159),C311 (470MFd),R355(27Ω),R356 (24Ω), C313 (47MFd), R317-R316 (680Ω) C312 (10MFd), Q306 (C2073), Q307 (A940), R325 (330Ω),Q303(C2229),D303 (5.6V-zener),R332 (4.7Ω), R333 (1Ω), D304 (1N4148);
C316 (470MFd), vertical def coil & its wire, R323 (1.8Ω), C317 (4.7MFd), C318 (3K3pF), R312 (24K), R313 (15K), R314 (20K), R316 (9K) R30 (3K3), R255 (50K), R311 (24K), C308 (2.2MFd), 0312 (5V-zener), R320 (1K), C306 (0.22MFd), R308 (39K), R34A (220K), & 351 (220K), IC DBL2003/TA7698AP.
Height Less or Cinemascope Picture &/or Vertical Non Linearity &/or Vertical Fold-Over Problem, Sound Normal:
Adjust & check R255 (50K), less or abnormal supply to vertical section, R327 (10Ω), D302 (BY159), C311 (470MFd), R355 (27Ω), R356 (24Ω), C313 (47MFd),
Only Red Colour With Retrace Lines, Sound OK:
CRT red cathode voltage will decrease. R591 (15K/2W), Q507 (C2229) & related parts, VR257 (10K), fault In circuit between pin no 21 of IC501 & CRT red cathode, IC DBL2003/TA7898AP, CRT red cathode def, CRT base.
Only Green Colour with Retrace Lines, Sound Normal:
CRT green cathode voltage will decrease R902/ (15K), Q508 (C2229) & related parts, VR258 (10K), VR253 (200Ω), fault in circuit between pin no 20 of IC501 & CRT green cathode, IC DBL2003/TA7698AP, X^RT green cathode def, CRT base.
Only Blue Colour With Retrace Lines, Sound OK:
CRT blue cathode voltage will decrease R593 (15K), Q509 (C2229) & related parts, VR259 (10K), VR252 (200Ω), fault in circuit between pin no 22 of IC501 & CRT blue cathode, IC DBL2003/TA7698AP, CRT blue cathode def, CRT base.
Only Secondary Colour Cyan (Red Colour Missing), Sound Normal:
CRT red cathode voltage will increase. R901 (4K7), Q507 (P2229), VR257 (10K), C531 (1KpF), R540 (150Ω), R265 (120Ω), C534 (180pF), R527 (560Ω).D502 (1N4148), R522 (2K7), fault in circuit between pin no. 21 of IC501 & CRT red cathode, IC DBL2003/TA7698, CRT red cathode def, CRT base.
Only Secondary Colour Magenta (Green Colour Missing), Sound Normal:
CRT green cathode voltage will increase. R902 (4K7), Q508 (C2229), VR258 (10K), C543 (1KpF); C582 (1KpF), R541 (150Ω), VR253 (200Ω) R525 (560Ω), D501 (1N4148), R524 (2K7) Fault in circuit between IC501 pin no 20 & CRT green cathode, CRT green cathode def, IC DBL2003/TA7698, CRT base.
Only Secondary Colour Yellow (Blue Colour Missing), Sound Normal:
CRT blue cathode voltage will increase.R903 (4K7), Q509 (C2229) VR259 (10K).
C533 (1KpF), R542 (1503), VR252 (200Ω) C536 (180pF), R526 (560Ω), D503 (1N4148), R522A (2K7), fault in circuit between pin no 22 of IC501 & CRT blue cathode, IC DBL2003/TA7698, CRT blue cathode def, CRT base.
Less & /or Distorted Sound, Picture OK:
Less or abnormal supply to Sound Section, R601 (6.2Ω), C602 (470MFd), speaker paper cone torn or hard, C601 (470MFd), R602A (6.2Ω), C607 (0.1MFd), C608A (47MFd), IC601 (TOA2611), C605 (0.1MFd), C606 (2K2pF), R605A (56K), R102B (2K2), Q601 (A1015), R622 (2K2), R624 (39K), R623 (1K5), R102A ?2K2), RS1 (10K), CS1 (6800pF), C608 (10MFd), R618 (160K), R617 (4K7), C618 (22MFd),
Present Layout Diagram
Figure 30
Actual Shorting Shunt Position of Jumpers
Glossary ACC: Automatic colour control.
Aperture Mask: A metal plate with framed holes, placed closely behind the phosphor dot coated screen in a colour T.V. picture tube. Its function is to ensure that each of the three electron beams strikes only the desired colour phosphor dot associated with the beam. This is also known as shadow beam.
Aspect Ratio: Ratio of the width to height of picture frame.
Active Lines: The television image lines actually visible on screen of picture are 625.
Out of these 585 are active, the remaining occur during the vertical retrace period, when the viewing tube is blanked out.
Aquadag Coating: It is the conductive graphite coating on inside glass wall of the picture tube funnel or bell, that extends from face plate or screen to about halfway into the narrow neck. This coating acts as final anode.
AFT: Automatic fine tuning - an arrangement used in colour T.V. receivers to automatically check and correct the frequency of the local oscillator in the tuner. This ensures that the video IF remains at the correct value and eliminates the need of frequent adjustment of the manual fine tuning control.
AGC: A circuit arrangement, which adjusts the gain of the receiver and keeps the output relatively constant, in spite of variation in strength of input at aerial.
Balun: An impedance matching device for antennas used between transmissions.
Bar Generator: A generator for producing pulses equally separated in time that are synchronized so they produce a stationary bar pattern on a television screen for test purpose.
Blanking: The process of applying negative voltage to the control grid of CRT to cut off the electron beam during the retrace or fly back period.
Boost Supply: A high voltage D.C. supply produced in a horizontal output section.
This boosted +B supply voltage is commonly used for horizontal output tube, vertical oscillator and first anode of picture tube.
Blooming: Increase in picture size due to over sweeping because of reduced high voltage to final anode of CRT.
Beam: The stream of electrons passing from the cathode to the fluorescent screen of a cathode ray tube.
Burst Gate: 8 to 10 cycles of the sub carrier are transmitted in the back porch of the horizontal sync signals. The signals are used for synchronizing the regenerated sub carrier and for obtaining the identifying signal for phase reversed V lines as well to separate these signals a part of the CVD signal is given to the burst gate. The burst gate which is controlled by the line sync pulses allows the signal to pass only during the burst period. Thus it separates the burst signal.
Corona: A point at high potential can ionize the surroundings air to produce a visible corona effect, which is light blue in colour. This causes loss to power.
Cascode Amplifier: An amplifier circuit using twin triode tube to provide better gain and less noise.
Clamping: Keeping one amplitude at constant level, e.g. the blanking level can be clamped at grid cut off voltage for picture tube. The clamping function is really the same as DC insertion or DC restoration.
Chrominance: A colour term defining the hue and saturation of a colour.
Chrominance Signal: The U and V sidebands of the modulated colour sub - carrier.
These carry information pertaining to the hue and saturation of the colour but no information regarding the brightness.
Choke Coil: It limits the flow of alternating current while allowing direct current to pass.
Colour Burst: A synchronizing signal consisting of about 10 cycles of colour sub-carrier oscillator in the transmitter. It is transmitted during the back porch of the line sync signals and is used to synchronize the colour sub carrier oscillator in the colour TV receiver.
Colour Edging: Extraneous colours appearing at the edges of coloured objects and differing from the true colours in the object.
CCVS: Composite colour video signal or composite video signal in colour TV receivers. This includes the luminance signals, coded chroma signals, sync signals and the colour sub carrier burst. .
Complementary Colour: A colour formed by subtracting a sample colour from white light. For example if red is subtracted leaving green and blue the complementary colour is cyan.
Convergence: The cross over of the three electron beams of the three gun tricolour picture tube. This occurs at the plane of the aperture mask.
Chroma Delay Line Decoder: The U & V signals are transmitted on a single sub carrier. This is known as quadrature modulation. The function of chroma delay line decoder is to separate the modulated U & V components from the quadrate modulated
Delay Line: A time delay device consisting of an actual or artificial transmission line, its purpose in colour TV receivers is to ensure the coincidence of the luminance(Y) and the chrominance (U and V) signals.
Deflection Yoke: An assembly of one or more electromagnets to produce deflections from one or more electron beams.
Detection: Stage in which demodulation or detection takes place.
Dropping Resistance: A resistor used to decrease the voltage in a circuit.
Damper Diode: Damper diode conducts immediately after horizontal retrace to damp the oscillation in horizontal scanning current, which would otherwise produce thin white vertical lines in raster. Also damper action produces boost supply for anode of horizontal amplifier tube. Finally the damper current provides horizontal scanning for the left side of raster that is why damper diode is also called efficiency diode.
Efficiency Diode: Damper diode is also called efficiency diode, because when it is conducting it provides horizontal scanning from extreme left to one third of the length.
Equalising Pulses: In television signals the two pulse trains of 6 pulses each which occur just before and just after a vertical synchronizing pulse. Equalizing pulses are short duration pulses. Interval between two adjacent pulses corresponds to horizontal scanning cycle. This is meant to keep horizontal deflection oscillator ready for reversal of direction of current.
Fly Back: Retrace, or return time the period during which an electron beam that has concluded one scanning sequence returns to the starting point.
Frame: The complete picture or scene to be scanned is called frame it consists of 625 horizontal scanning lines.
Gray Scale: In a test pattern a scale that illustrates uniform changes in signal amplitude from white, progressing through Gray values in equal steps to black.
Hum: A low audio frequency, having the same frequency as that of the power supply or a harmonic there of introduced, into the signal paths by inductions, leakage or insufficient filtering and heard in the back ground or a received radio programmer or appearing across a television image in the form of one or two horizontal bars.
Hue: The dominant wavelength of light representing the colour of an object. It is the redness, blueness or greenness of an object.
Hybrid Receiver: In this type, the deflection circuits generally use power tubes, while the signal circuit use transistors and ICs. These receivers usually have filaments connected in series chain.
Hold Control: A TV receiver has vertical hold control. The vertical hold control adjust the frequency of the vertical oscillator close enough to 50 Hz so that it is locked by incoming sync pulses.
Ignition Interference: Interference produced by auto ignition sparks or other ignition discharges.
Image: A reproduction of a person, object or scene such as that produced by a television receiver.
Impregnate: To treat component so as to make it moisture resistance by filling the excess space in its container with a material such as a wax or pitch.
Infra Black Region: The portion of the video signal above the black level. It contains the synchronizing pulses.
Inter carrier Sound: The RF sound carrier is 5.5 MHz above the picture carrier. All
Inter carrier Sound: The RF sound carrier is 5.5 MHz above the picture carrier. All