Overall Protection Block - Sony DTV-01 Manual

Overall Protection Block

Protection
The protection circuitry on the G and D boards monitor the following
items and shuts the TV off if there is a problem:
G Board:
Vertical deflection loss (self diagnostics - light indication)
+5V OCP monitored (self diagnostics - light indication)
+5V OVP monitored (self diagnostics - light indication)
+135V OCP monitored (self diagnostics - light indication)
+135V OVP monitored (self diagnostics - light indication)
+15V OVP
Surge relay RY5502 not energized.
D Board:
Driver supply voltage OVP
H. Output OVP
H. Output OCP
FBT Output OVP
H Centering IC4003 OCP
Four general failure detectors on the G board not only shut down the
TV set but also inform the Main Micro IC3251 of the failure. The Main
Micro IC3251 provides a blinking light indication of the failure. This
micro routine is called the self-diagnostic program and found in many
Sony Trinitron TV sets made since late 1997.
Self Diagnostics
This TV also has self-diagnostics circuitry that is connected to five
sensing circuits. A failure detected by one of these circuits is regis-
tered by the Main Micro IC3251 and permits it to blink the front panel
standby light a number of times to identify the problem area.
67
S ta n d b y L ig h t In d ic a tio n
# tim e s S h u td o w n c a u s e /
lig h t S y m p to m
b lin k s
2 B + O C P / T V S h u td o w n
3 B + O V P / T V S h u td o w n
4 S e ria l D a ta s h u td o w n
in s tr u c tio n fr o m D e fle c tio n
C o n tr o l IC 1 3 0 5 to M a in
M ic r o IC 3 2 5 1 .
/ T V S h u td o w n
5 S ta n d b y lig h t b lin k s 5
tim e s a n d re p e a ts .
W h ite s in th e p ix a re n o t
w h ite . S o u n d O K / V id e o
P ro c e s s o r IC 3 0 0 5 c a n 't
W h ite b a la n c e (IK fa ilu re ).
T h is fa ilu re w ill n o t s h u t
d o w n th e T V s e t.
6 + 5 V O V P , O C P /
T V S h u td o w n
Further details about the self-diagnostics circuitry and its OSD for inter-
mittent problems are explained in the service manual.
Repair Strategy
The strategy for identifying the cause of the TV shutdown is the same as it
would be for a projection TV or even a camcorder:
1. Note the symptoms like # relays clicked, frying noise, blinking lights,
station sound, OSD, etc.*
2. Check power handling devices or common failures such as the Hori-
zontal, Vertical, Audio, and Video output ICs for shorts.
3. Narrow the problem to a board
4. Isolate the problem to the circuit using the descriptions in the protec-
tion circuitry diagrams that follow.
P o s s ib le d e fe c tiv e c ir c u it
H o riz o n ta l d riv e r, h o r iz o n ta l
o u tp u t, F B T , o r P W M .
D y n a m ic fo c u s c irc u it &
P in c u s h io n c o r re c tio n c irc u it.
C o n v e rte r 1 :
•
re g u la tio n fa ilu re
•
o s c illa to r o ff fre q u e n c y
V e rtic a l fa ilu re
H o riz o n ta l s c a n (F B T ) d e riv e d
v o lta g e fa ilu re (n o H o r iz o n ta l)
L o w c o n v e rte r 1 o r 2 v o lta g e s
(c a u s in g lo w s c a n v o lta g e s )
S c re e n c o n tro l s e ttin g to o lo w .
V id e o p r o c e s s o r o r v id e o
o u tp u t s ta g e fa ilu re . S e e v id e o
p ro c e s s .
In c o rr e c t C r o r C b d a ta in th e
s e r v ic e m o d e .
C o n v e rte r 2 r e g u la tio n .
S h o rt o n + 5 V lin e .