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TECHNICAL UPDATES - TOSHIBA (1992 ONWARDS)

TV UPDATES

2100TBT
(1) FAULT SYMPTOM - Intermittent display of AV symbol on the screen.
CAUSE - Dry joint on red lead located on the component side of the PCB, between point C and point C.
CURE - Resolder.
(2) FAULT SYMPTOM - HT low, power supply pulsating, +300v rail measures normal.
CAUSE - C820 120mfd capacitor open circuit.
CURE - Replace C820 Part No.24086871

2500TBT
(1) FAULT SYMPTOM - Diagonal black lines on colour (or coloured lines) that vary with colour control setting.
CAUSE - C515 22mfd open circuit, can show rust type contamination.
CURE - Replace with 50v electrolytic capacitor.

2112DBT
(1) FAULT SYMPTOM - No colour at switch on comes on after a few minutes not affected by heating or freezing.
CAUSE - Q546 open circuit base-emitter (when cold).
CURE - Replace Q546 BC547A Part No.23114689.
(2) FAULT SYMPTOM - Intermittent turn off (line oscillator circuit shuts down).
CAUSE - On this model, video colour and deflection IC (IC501) TA8783N pin 52 senses sudden increase in beam current and disables line oscillator drive.
CURE - Remove R844 1meg ohm resistor and fit 330k ohm resistor in parallel with C543 capacitor. This prevents spurious operation of this circuit.

259D9B
(1) FAULT SYMPTOM - Crackling on Nicam sound.
CAUSE - R111 10 ohm resistor open circuit, located on rear terminal PCB.
CURE - Replace R111.

TECHNICAL NOTE - The circuit references for CG60/RG34 and CG48/RG30 C/R networks are reversed in the Nicam circuit. Please correct your circuit diagram.

1400TBT
(1) FAULT SYMPTOM - Intermittent frame collapse. (HT line fluctuates when warm).
CAUSE - Q803 2SC3245 Transistor faulty.
CURE - Replace Transistor part no: A6361601
(2) FAULT SYMPTOM - Low HT volts or stuck in standby.
CAUSE - Q803 2SC3425 Transistor faulty.
CURE - Replace Transistor part no: A6361601.

145R7B
(1) FAULT SYMPTOM - Repeat failure of Diode D808 in power supply.
CAUSE - Faulty capacitor C813 47mfd 50volt.
CURE - Replace capacitor part no: 24797470.

1510RB
(1) FAULT SYMPTOM - Set dead and making buzzing noise.
CAUSE - Transistor Q803 2SC3425 faulty.
CURE - Replace Transistor part no. A6361601.

155R9B, 155T9B
(1) FAULT SYMPTOM - Line shift fault, black band down right hand side of screen.
CAUSE - D403 6.2 volt Zener diode faulty.
CURE - Replace Zener diode part no: 23115604. Also replace Resistor R402
12kohm part no: 243661123.

1721TB
(1) FAULT SYMPTOM - Stuck in standby.
CAUSE - Transistors Q803 2SC2023 and Q804 2SA1321 faulty.
CURE - Replace Transistors part no's: 23314246 and A6547303.

2100RBT, 2100TBT
(1) FAULT SYMPTOM - Hum on Chroma (varies with colour control setting).
CAUSE - C515 22mfd 50volt capacitor faulty.
CURE - Replace capacitor part no: 24636220.
(2) FAULT SYMPTOM - Set dead, Q802 Transistor fails repeatedly at switch on.
CAUSE - Resistor R810 330k either open circuit or high value.
CURE - Replace resistor.

210T6B
(1) FAULT SYMPTOM - No luminance.
CAUSE - Diode D213 faulty causing incorrect DC level at IC501 pin 3.
CURE - Replace D213 ISS104 part no: A7150041.
(2) FAULT SYMPTOM - No video.
CAUSE - Capacitor CV03 0.01mfd faulty.
CURE - Replace capacitor part no: 24232103.

2112DB, 2512DB, 2812DB
(1) FAULT SYMPTOM - Frame jitter and picture breathing.
CAUSE - Transistor Q833 S1854 faulty.
CURE - Replace Transistor part no: A6907751.
(2) FAULT SYMPTOM - Will not go into standby.
CAUSE - Transistor Q845 2SC2023 S/C.
CURE - Replace transistor part no: 23314246.

2505DB, 2805DB
(1) FAULT SYMPTOM - Will not come out of standby.
CAUSE - At power on set immediately reverts back to standby. Logic signal from micro. Pin 37, drops low to start then reverts back to 5v.
CURE - Replace ICA07 memory IC part no: 23319016.

2527DB, 2927DB, 3327DB
(1) FAULT SYMPTOM - Crackle on Nicam, FM and external audio.
CAUSE - IC ICG07 TA8776N. Audio processor on back terminal PCB faulty.
CURE - Replace IC part no: B0383935
(2) FAULT SYMPTOM - Dead, Power and Timer LED'S flashing. (HT 40v and varying).
CAUSE - Transistor Q828 2SC2230A-Y faulty.
CURE - Replace transistor part no: A6325067.

1720RB
Fault Symptom - Line tearing after two hours.
Cause - Q801 STRD4412 in power supply, failing at high temperature. This can be proven by heating and freezing.
Cure - Replace Q801, Part No. 23314510.

2103TBG
Fault symptom - No line or field sync.
Cause - 5v supply missing from text module Pin 12 (CCT 5v). RF80 1/2W 10 ohm fusible safety resistor, is O/C.
Cure - After confirming that no fault exists in the text module. Replace RF80 with correct type safety resistor Part No. 24531100.

2112DB, 2512DB, 2812DB, 2527DB, 2927DB, 3327DB, 2539DB, 2939DB, 3339DB.
Fault Symptom - Black flashing lines running up the screen.
Worsens as set warms up.
Cause - ICV01 TA8777N A/V switching IC has internal fault, which is temperature sensitive.
Temporarily cured by freezing.
Cure - Replace ICV01 Part No. B0383941.

2535DB, 2835DB.
Fault Symptom - Set dead. power supply in over voltage protection mode, main HT rail measures 11v instead of 125v.
Cause - Circuit protector ZP81 O/C.
Cure - Replace circuit protector ZP81 PRF5000 Part No. 23144451. Check the following for S/C:-
IC670 TA8218AH ( Part No. B0377305).
Diodes D670, D671, D672, D673, D674, and D675 all 1N4148 ( Part No. 23115599 ).
NOTE - Under fault condition, IC801 pin 9 voltage varies between 5v and 8v, Output voltage control loop is inoperative since IC826 (photo coupler) has no supply.

2500TB
Fault Symptom - Picture visible for a few seconds only, then goes to blue mute. During this time the top third of the screen is mainly flyback lines and the lower section is stretched out.
Cause - R448 resistor has gone high in value from 2.7 ohms to 23 ohms, resulting in IC501 (video colour and deflection IC ) TA8659AN 12v supply to pins 6 and 61 to read only 8v.
NOTE - If audio plug P602 is pulled out set will not blue mute, so the fault symptom can be seen.
Cure - Replace R448 safety resistor with correct type
Part No 4984279