Sharp 51AT15H Technical Bulletin

TELEVISION TECHNICAL BULLETIN
MODELS 51AT15H
SYMPTOM Vertical stage problems
ACTION Listed below are a few fault conditions and their suggested remedies
Fault
Output transistors running hot
No front button operation
Will not come out of standby
Top of frame distorted
Too much height
Fold over at the top of the frame
Cramping (top or bottom)
Loss of picture (may be intermittent)
Notes
1. When replacing semiconductors in the vertical output stage, it is strongly recommended that all parts are purchased
from the Sharp Spare Parts Center or Willow Vale Electronics using the part numbers in the service manual
(reproduced on page two).
2. C713 must be replaced with a high temperature type (use the part number below).
3. Always check the +5Vb line fed into the bias network of Q507. If Q708 (+5Vb regulator/switch) goes leaky it may
cause intermittent operation problems, but the fault symptom appears to be the vertical stage.
4. If the vertical pulse to the microprocessor is missing or distorted (pin 46 of IC1001), then the key scan will not work.
5. Q509 must be the correct device.
6. When R508 is open circuit, both vertical output transistors turn on, thus overloading the power supply. This can
cause the power supply to buzz.
7. Q503 (BC828) may be a BD830 supplied as an alternative under part number RH-TX0204BMZZ.
8. Q509 (BC635) may be supplied under an alternative part number – RH-TX0118BMZZ. This is an identical device.
White – Carry out as required, Yellow – Carry out as required and whenever the unit comes in for service, Red – Carry out on all units
Sharp Electronics (UK) Limited
Reference TB-T9905070
Revision 1
Month of Issue: July 1999
Classification:
Counter measure
R508 high or open circuit
D506 leaky
R508 open circuit
C501 and/or C514
Change R520 to 68kΩ (was
56kΩ)/R508
Scanning coils (should read 9.9Ω)
D709, C713 and check all
semiconductors in vertical stage
D504 and/or C502 leaky
CTV990704
White
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