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a. High voltage shut down. b. Monitor will have ‘tic - tic’ sound. Sometimes
capacitor may measure O.K. but break down when under full operating voltage. c. Horizontal output transistor will blow in a few hours or days after you have replaced it. d. Sometimes it will cause intermittent "no display". e. Distorted display i.e.,
display will go in and out. f. It will cause horizontal output transistor to become shorted and blow
power section.
How to check if a primary winding is good or bad in a Flyback Transformer? a) By using a flyback/LOPT tester, this instrument identifies faults in primary winding by doing a ‘ring’ test. b) It can test
winding even with only one shorted turned. c) This meter is handy and easy to use. d) Just simply connect
probe to primary winding. e) The readout is a clear ‘bar graph’ display which show you if
flyback transformer primary winding is good or shorted. f) The LOPT Tester also can be used to check
CRT YOKE coil, B+ coil and switch mode power transformer winding.
NOTE: Measuring
resistance winding of a flyback transformer, yoke coil, B+ coil and SMPS winding using a multimeter can MISLEAD a technician into believing that a shorted winding is good. This can waste his precious time and time is money.
How to diagnose if
internal capacitor is open or shorted? By using a normal analog multimeter and a digital capacitance meter. A good capacitor have
range from 1.5 nanofarad to 3 nanofarad.* 1) First set your multimeter to X10K range. 2) Place your probe to anode and cold ground. 3) You must remove
anode cap in order to get a precise reading. 4) Cold ground means
monitor chassis ground. 5) If
needle of
multimeter shows a low ohms reading, this mean
internal capacitor is shorted. 6) If
needle does not move at all, this doesn’t mean that
capacitor is O.K. 7) You have to confirm this by using a digital capacitance meter which you can easily get one from local distributor. 8) If
reading from
digital capacitance meter shows 2.7nf, this mean
capacitor is within range (O.K.). 9) And if
reading showed 0.3nf, this mean
capacitor is open. 10) You have three options if
capacitor is open or shorted. - Install a new flyback transformer or - Send
flyback transformer for refurbishing or - Send
monitor back to customers after spending many hours and much effort on it.
* However certain monitors may have
value of 4.5nf, 6nf and 7.2nf. Note: Sometimes
internal capacitor pin is connected to circuits (feedback) instead of ground. Tv rca flyback transformer circuits usually do not have a internal capacitor in it. If you have a flyback diagram and circuits which you can get it from
net, that would be an advantage to easily understand how to check them.

Jestine Yong is a electronic repairer and a writer. For more electronic repair articles please visit his website at http://www.noahtec.com/electronic-repair-articles.htm