Sharp 37EM-33H (serv.man16) Service Manual / Technical Bulletin ▷ View online
Sharp Electronics (UK) Limited
Reference AVW150299/1
Revision 2
White – Carry out as required, Yellow – Carry out as required and whenever the unit comes in for service, Red – Carry out on all units
CTV990202
Month of Issue: Febuary 1999
Classification: White
TELEVISION TECHNICAL BULLETIN
Page 1 of 1
MODELS
37DM23H 37DT25H 51DT25H
Common faults on the CA1 Chassis
Fault Reason Possible Cause
No teletext Low video input to pin 30 of IC1001 (should be 2.5V). Q201 or Q801
Buzz on sound Noise on audio IF signal or AFT VCO adjustment
incorrect
Q801 or poor adjustment of the AFT
VCO
VCO
Erratic start up problems Noise corrupting operation of IC1001/201 See Technical Bulletin CTV981205
Vertical stage problems Various component failures. Note that as the vertical
output stage is DC coupled, a problem at the start of the
stage can have a dramatic effect on the output.
stage can have a dramatic effect on the output.
Check all components in the vertical
stage, paying particular attention to
R507/8/22, C510/2/14 and C713
stage, paying particular attention to
R507/8/22, C510/2/14 and C713
No start up Power supply failure Q702 and/or D718 short circuit
Dead set Power supply running, but no picture and sound – reset
pulse problems
Q704 and/or Q1012
Low HT (40V) Fedback control for the power supply incorrect Check components around the opto-
coupler
Note that the CA1\CA10 chassis training course notes are available on the Sharp Electronics (UK) Limited Web Site
(
(
WWW.Sharp.Co.UK/Tech
) under the models fitted with these chassis - grouped under the Service Manual heading.
These notes contain in depth details on circuit operation. Please refer to these while fault finding.
If you have a fault to add to the above list, please do no hesitate to contact Sharp Technical Support via the Hot Line
telephone number.
.
telephone number.
.
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