Sony CTV-25R1, Manual

Page: 105 / 108

101
Failure Checklist
Times Standby
Light Blinks Possible defect
2
(Excessive current
or FBT amplitude) 1. Horizontal Output Transistor leaky/shorted.
2. Flyback shorted.
3. Flyback secondary load is shorted.
4. Safety/resonate capacitor opens (C508 in this set).
5. Sensing circuit defect (IC521, Q571 and Q300).
6. No reply from Jungle IC301.
4
(Vertical failure) 1. Vertical Output IC541 failure.
2. Open R549/open foil path.
3. Shorted D549.
4. IC001 damaged by open D001.
5. No vertical drive from IC301/pin 13 and 14.
6. No vertical IC541 +13Vdc power from FBT (horiz
drive failure).
5
(Loss of green IK
signal to
IC301/pin 21)
•
Green buffer transistor Q393 open or shorted.
•
Protection diode D706 shorted.
•
CRT amp IC701 defective.
•
Picture tube socket not making contact.
•
IK amplitude limiter Q302 or zener D302 damaged by
picture tube arcing.
Once a second Jungle IC communications failure.
When the problem is intermittent, you will have to probe further by moni-
toring the horizontal output transistor temperature and the TV’s current
consumption to see if it is high, vibrate and possibly “bake” the set to
force the intermittent failure to reveal itself.
Memory Clear:
Unplugging the TV from AC power resets the stored failure information
and stops the blinking light. The memory is cleared once s5Vdc
is removed from the Control Tuning System Microprocessor IC001. It
can also be manually cleared by first pressing 8 and then pressing EN-
TER while you are in the self-diagnostic mode.
Clearing the Self-Diagnostic Memory
Method Steps
A. Unplug the TV from AC. Removing AC power clears the
memory at any time.
B. From the remote control. Press buttons:
8, then press ENTER.
Self Diagnostic Exit:
Shutting off power to the set retains the memory information and allows
you to return to the TV picture.
Self Diagnostic Circuit
The self-diagnostic program is contained in the Control Tuning System
IC001. The number of problems is detected by the program is stored in
IC001. This number remains in IC001’s resident memory as long as the
TV remains plugged into AC and is not manually cleared.
Inputs
When the TV set is turned ON, IC001 monitors three TV conditions using
two inputs at pins 37 and 17. These TV conditions are:
1. Vertical Failure - In normal operation, Vertical Output IC541’s “Ref”
pin 3 outputs a 30Vp-p pulse (1msec pulse width). This voltage is
reduced by R549 and clamped to no higher than 5Vp-p by D001.
These vertical pulses from IC541/pin 3 are monitored by Control Tun-
ing System IC001 at pin 17.
A vertical drive failure causes no pulses to be generated. If these
vertical pulses are lost for two seconds, IC001 will turn OFF the TV to
prevent the vertical deflection failure from damaging the CRT. How-
ever, the front panel Timer/Standby light continues to blink four times,
pauses and repeats, even though the set is OFF.
2. Excessive Current Demand/Excessive FBT pulse amplitude – Y/C
Jungle IC301 monitors both of these conditions at input pin 18. Nor-
mally there are horizontal pulses applied to IC301/pin 18 when the
TV is ON.
When there is excessive current being drawn by the FBT or Horizon-
tal Output Transistor, the horizontal pulses are grounded out. The Y/
C Jungle IC301 detects this loss from pin 18 almost immediately and
sends data from IC301/pin 35 to IC001/pin 37 (even in normal opera-
tion, there is always data on this line). IC001 shuts OFF the TV to
Some of the reasons for the failure could be in this checklist.