This TV has no power symptoms-first I checked the fuse and it was blown but not blacked inside meaning there was no heavy short in the supply.
Remember a fuse can
tell you a lot about the last moment of any equipment before it died (in
medical terms postmortem)
1.
Fuse blown, dark inside - Means the machine died due to
heavy short. Please be sure to use the light serious Lamp to bring up the
machine after replacing the fuse.
2.
Fuse blown, clear inside- Means the fuse might have died
through natural dead (e.g. old age)
After I replaced the
fuse it didn’t blow again confirming to me that there was no serious shorted component
(I mean component shorted which is taking the supply directly to the grounds).
I measured the output
voltages and there was none: absolutely zero volts. Then I checked the voltage
at the main capacitor and it was 320 v dc which is okay. The voltage was also
reaching the switching transistor collector same voltage.
I measured the S.O.T
base voltage and it was 0.02 volts. I followed the start up circuit divider and
the voltage was ok and no resistor was open.
But from the above
voltage measurement you find the Zero volts at the base of the S.O.T is
suspect.
Either the S.O.T (v513)
is sorted base-emitter because it’s taking the voltage to the ground. ). Or
V512(c3807) is shorted collector-emitter because it’s also taking the base of
the S.O.T to the ground. Or capacitor
c517 across the collector emitter of v512 (c3807) is shorted to the ground.
I removed the two
transistors i.e. S.O.T (v513) and driver v512 and measured them out of circuit
together with cap c517.
To my surprise the
S.O.T v513 (D1710) was shorted Base-Emitter junction i.e. was 82 ohm both ways on
diode test on my Dmm. meter. It should have been high and low (I mean the B-E
junction has two reading meaning the transistor is shorted B-E junction which
is very rare.
After replacing this Transistor
(chopper) and the broken fuse the machine was back to life.
Conclusion
If there is zero
voltage at the output then most probably the primary section is the cause of
the problem.
Narrow down to the
faulty circuit (area) by use of voltage testing only. This one is a very fast
and valuable method I have come to learn.
ARE YOU THE ONE?
- You have gone to college of electronics and completed the course with distinction but coming to the field you realized that repairing CRT TV is not a walk in the park.
- You are technician for over 5 years and your workshop is full of junk board and TV waiting for the owners to collect as un-repairable
- You are a technician and you find most of your work is to replace faulty TV board with universal TV board...
- You are a technician and you hardly diagnose and repair more than 3 TVs in a day
- You are just from school and want to do electronics repair as a career or part time job...
- You have another job and want to supplement your income by repairing TVs for your friends and neighbors...
- You are a technician and still there are some things you feel shy to ask your friend about repair thinking that they will consider you under dog...
- Whenever you open a TV for repair you feel intimidated by the numerous components in there.
- You are in TV repairs business but not able to pay your bills from your repair income.
This book can change your story to this.........
Hie Mr. Mndaka,
Once again I have written this to appreciate for your
extra-ordinary help about the China TV displaying the vertical line.
After reading your e-book I just went straight to the coils
in the horizontal circuit and the first one to change was L441, as soon as I
replaced this coil I switched on the set to see if it was the cause. Wow! My
eyes were astonished to see the Set being resurrected from the hell. Full screen and audio still there. It didn't
take me even 20 minutes.
It’s really great to have known you and I believe if I could
have known you two years ago I could even have been fixing Television sets with
my eyes closed by now.
May God bless you
Regards-Wilson
South Africa
My Latest best seller eBook
CRT television troubleshooting guide
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