I have a transistor that passed on 2 of my transistor testers BUT...... failed on the old digital VOM test. It failed on the test where you go positive on collector and neg to emitter - should read O/L for NPN, doesnt, it reads .5v. Transistor is 13005D. Any thoughts
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NPN transistor good or bad
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Re: NPN transistor good or bad
How about pos on E and neg on C?
Any thing connected to the Base while testing?
How about resistance in both direction?
Last edited by budm; 06-22-2018, 10:04 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: NPN transistor good or bad
With the price of transistors these days , my rule is usually "if in doubt change it out" Normally I dont used a transistor tester i just used a multimeter and if is passes there I call it good , I certainly wouldnt use 2 or more different testers because it can muddy the waters as you are seeing . My personal opinion is that there is a diode in it between collector and emitter . This would give you the results you are seeing .
Last edited by RepairNewbie47; 06-22-2018, 11:23 PM.
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Re: NPN transistor good or bad
Originally posted by johnfin View PostI have a transistor that passed on 2 of my transistor testers BUT...... failed on the old digital VOM test. It failed on the test where you go positive on collector and neg to emitter - should read O/L for NPN, doesnt, it reads .5v. Transistor is 13005D. Any thoughts
That may have caused wrong results while troubleshooting this thread: https://www.badcaps.net/forum/showthread.php?t=65349Last edited by budm; 06-23-2018, 12:57 AM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: NPN transistor good or bad
I have an analogue meter for testing Bi-polar transistors and diodes. With the transistor out of circuit and the meter set at Rx1000 placing the RED lead on the Base and the BLACK lead on the Emitter and then on the Collector if I get a reading near to 0 ohms and then switching the RED lead to the Emitter and Collector with the BLACK lead on the Base and get no reading or infinity I can safely say the transistor is good or bad. I would also make a check across the Emitter and Collector in both directions and if it is good it would read open provide of course there is no diode across the Emitter/collector junction.
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Re: NPN transistor good or bad
With three leads, there are six possible combinations to test.
Transistors usually fail open/short on one junction so it's easy to find.
But some transistors are a bit leaky or slightly damaged, and diode test looks fine but ohms reveals a damaged, leaky junction.
I use diode-test, do all six, and then repeat on ohms. So that's 12 readings for a thorough test. Important to do when fixing audio amplifiers.
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Re: NPN transistor good or bad
Originally posted by redwire View PostWith three leads, there are six possible combinations to test.
Transistors usually fail open/short on one junction so it's easy to find.
But some transistors are a bit leaky or slightly damaged, and diode test looks fine but ohms reveals a damaged, leaky junction.
I use diode-test, do all six, and then repeat on ohms. So that's 12 readings for a thorough test. Important to do when fixing audio amplifiers.
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Re: NPN transistor good or bad
Originally posted by RepairNewbie47 View PostThats why i just tend to shotgun replace them if they are fairly old . As you say they can test good sometimes and still be knackered . If I`m working on audio gear especially I will just go ahead and replace the lot .
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Re: NPN transistor good or bad
Sony professional broadcast/studio service manuals advised to always replace the transistor ahead of the last bad transistor found.
Even though it tests OK, it can be weak or damaged and will fail. For the old techs that can remember, this was in the 1980's and stopped a lot of repair-warranty returns.
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Re: NPN transistor good or bad
Originally posted by redwire View Postsony professional broadcast/studio service manuals advised to always replace the transistor ahead of the last bad transistor found.
even though it tests ok, it can be weak or damaged and will fail. For the old techs that can remember, this was in the 1980's and stopped a lot of repair-warranty returns.
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