About Shorted Transistor
If you found any shorted transistor in the circuit , chances is very high there will be some other components that may have problem too. Do not directly turn the equipment On after the replacement of the transistor without checking the corresponding components. Dry joints, bad ESR capacitor, leaky diode and etc may cause the transistor to go short circuit. If you take the case of Benq LCD Monitor, the shorted C5707 transistors are usually caused by dry joints in the high voltage transformer or the tuning capacitor have problem and this capacitor have to be test with ESR meter as sometimes it will read good with digital capacitance meter.
So the rule of thumb is to make sure that all the corresponding components are tested good first before putting in a new transistor and power On. This method also applicable if you found any other shorted semiconductor like diode and IC.
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Reynaldo Chua
February 12, 2010 at 10:59 am
There was one time I bought a C5248 power Transistor but when I test it with my analog meter it turn out to be a PNP transistor I was surprise I did not believe that sometime big Transistor manufacturer do makes a mistake. So it is really wise to check first before installing the new parts.
admin
February 13, 2010 at 8:53 am
HI REYNALDO,
How do you test the HOT. You test the HOT with analog or digital meter and what is the brand of the meter. The reason i ask is because some meter especially the analog type have a reverse output.
Jestine
Rey
February 13, 2010 at 10:17 pm
Actually sir justine this power transitor was not use as a HOT in the monitor circuit it is use as transistor pincushion I have monitor brought in with Horizontal size problem so what I did I followed your book in Bonus Voltage testing by pressing the plus and minus key to solve the problem luckyly I found the ic thats controlling the size and there on I followed 8 pin IC (6358B)High Performance dual amplifier) pin One is the Vout and I trace all the way down and found this transistor to be shorted since it is not available in our area I ask somebody to buy outside town but the Transistor that he bought is mark c5248 but when I test it with the sanwa analog tester it turn out to be PNP so again I search the net and found out the C5249 is the same transistor except the power is higher so I grab a chance and bought it and test it before installling and the problem was solve the horizontal size is now back to normal and you can adjust it.
admin
February 13, 2010 at 10:30 pm
Hi Rey,
That was a good write up and base on your description, you seems to be good in troubleshooting (tracing the circuit). Keep up the good work and thanks for sharing.
Jestine
jayarathna
February 23, 2010 at 4:24 am
cheking transister photos
admin
February 23, 2010 at 6:13 am
Hi Jaya,
It is all in my ebook http://www.TestingElectronicComponents.com
Jestine