Transistor Tester

I came across a monitor that have lines slowly moving upwards the screen. I could not locate as where is the section that caused the problem. When I carefully look at the mainboard I saw one portion at the dynamic focus circuitry a bit dark in color so I presumed those transistors in the circuit must be working very hard. Checking the transistors and all related components to be in working condition. But when I use a coolant to spray the area I found that the lines disappeared immediately. I applied heat using hair blower and coolant again and found one of the transistors giving fault. That's mean when I spray the particular transistor the lines totally goes off.

I took out the transistor and checked with an analog meter and it measured ok. The problem surfaced when I checked the transistor with peak electronics atlas transistor tester. The hfe reading of a known good one compare to the bad transistor was totally off the tolerance. The transistor part number is KSP44 or equivalent to MPSA44. Replacing the transistor solved the lines problem. How I wish if I have either the b&k or sencore transistor tester which I believed is very accurate when checking any transistors including the Fet, scr and other three leg devices. The transistor problem mentioned above is very uncommon and generally an analog meter alone will do the job. Hair blower and coolant also contribute in helping us to find out the culprit fast especially in the 'intermittent' case. If you do not have the gadget above the only choice for you is to direct replace the suspected components and hope the problem could be solved.

Author By : Jestine Yong, he is a electronic repairer and a writer. For more information on electronic repair please visit his website at : http://electronic-repair.blogspot.com