Secondary Voltages; +135 Volts; Audio B - Sony WEGA KV27FV15 Training Manual

Secondary Voltages

+135 Volts

The signal from the winding of T605/10 and 11 is applied across D643
Bridge Rectifier and C643 and L642 filter the rectified voltage. D648 is a
150-volt zener diode that will limit the voltage to 150 volts in case of a
failure that causes the B+ to rise. This voltage is then sent through R652
and output from the G board at CN641/1 and 2. The voltage is used on
the G board by the protection and regulation circuits and is also used to
produce the +33 volt line on the A board.
+12 Volts
D651 and D652 rectify the signal from T605/7 and 8. This voltage is
filtered by C658 and input to IC650 12-Volt Regulator. IC650 outputs a
regulated 12 volts that is filtered by C661 and output from the G board at
CN641/8.
+9 Volts
The signal from T605/7 and 8 is applied to D642 through two similar par-
allel networks consisting of L650 and R670, and L651 and R670. This
rectified voltage is then applied to the input of IC641 9-Volt Regulator.
The output of this IC outputs 9.6 volts to L652 and also to CN641/6 and 7.
Shorted Supply Distribution
A Board - T503 Flyback, H Drive Q501, H Out Q502, Pin Amp Q512, WA board VM Drive Q946
+135
A Board - Q301 HP Buffer, IC353 SHP, All WA board except VM Drive
+12
A board - TU102 Tuner, IC351 VM Mute, IC352 YUV Switch, IC354 YUV Switch, IC355 Y/C Jungle, IC101 D/A
+9
Converter, AK Board - IC1401 Audio Processor, IC1403 SRS, Q1102 Tuner 5 Volt Regulator, C Board - Q1790 IK
Buffer, UY Board - IC2006 5 Volt Regulator, IC3302 5 Volt Regulator, IC3304 Chroma Decoder, IC3308 YUV Switch,
UY Board IC2005 3.3 Volt Regulator, IC2006 5 Volt Regulator for tuners,
IC3504 Comb Filter
UY5 from IC2006
IC3307 V Chip, IC3303 PIP Processor
UY5 from IC3302
AK Board - IC1461 Audio Output

Audio B+ (33

volts)
21
The voltage is 9.6 instead of 9 because D647 is connected between the
ground pin of IC641 9 Volt Regulator and ground.
+9 Volt Protection
The +9 volt line also is monitored for OCP. Using the voltage drop across
R680, R681 and R644 to control the conduction of Q649 does this. When
the amount of current drawn on the 9 volt line is sufficient to cause Q649
to conduct, Q650 will be turned ON. This places a LOW on the inhibit line
of IC641 9 Volt Regulator. When there is a LOW present at this pin, the
output of IC641 is disabled.
+5 Volts
The +5 volt line will not be discussed since it is not used in the set.
Audio B+
The signal from T605/5 and 6 is applied to D641 Bridge Rectifier. The
negative side of D641 is connected through R643 to ground; therefore the
Audio B+ floats slightly above ground level. The voltage output from D641
is filtered by C641 and then sent to CN642/1 and 2 unregulated. The
audio B+ is used only by the Audio Output Amplifier IC1461 located on
the AK board. One step in troubleshooting a set that is shut down is to
disconnect CN642. If the set still operates, then replace IC1461 Audio
Output. Be sure to discharge the voltage at CN642/1 and 2 before reat-
taching the connector to CN642.