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Checking shorted transistors

TIP: when checking transistors, if the transistor appears shorted in circuit, you need to test it outside the circuit. This is because they are sometimes across a coil and will therefore appear shorted while in the circuit, even though they aren't shorted at all.

To remove them from the circuit I find it's easiest to simply clip 2 of the 3 leads, test, and solder the lead back together if it's ok. If it's bad, I clip the third lead, and then desolder each leg individually...much less effort and time that way!

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My AV-502A main amplifier fuse was blown,I checked the power transistors and found 2 shorted,C5198.I replaced it with new one, but the fuses still blown up, including the new transistors.


There are several reasons. If you find one shorted transistor in a push-pull stage you should always replace both. One might be faulty but not shorted, but when in operation it does the other one in. You might have also missed another shorted part such as a diode or voltage regulator. Hunt around looking at the circuit of the confirmed shorted parts and test or replace anything off that circuit.
Finally check your speakers and wiring to them. Shorted output transistors have generally two ways of going like that. Wires touching each other or bad speakers, or having it too loud!

Feb 02, 2016 | Audio Players & Recorders

1 Answer

Channel A on my PMP 1280s is blown


This website appears to have diagram for it. You will have to register to log in. http://elektrotanya.com/?q=hu/content/how-change-site-language-english
May of been some other component burnt out. Only way is by test meter and testing. Quite possible transistor burnt out.
You should be able to test it in circuit for Short circuits.
If output transistors faulty make sure you check driver transistors as well. Hope some of that helps.

Nov 19, 2013 | Audio Players & Recorders

1 Answer

my amplifier fuse was blow when i try to turn on the power.after that i did replace with new fuse and then i try to turn on the power again but the fuse blow again.so what make it happen?can you help me solved this probelm?


You may have shorted output devices in the amplifier output section of the amp circuit...these are usually mounted to the heat sinks and are very large output transistors...if you have an ohmmeter available you can test the outputs...there are 3 leads on each output...you want to test the transistors by putting the ohmmeter in the diode test mode and then put the leads on the transistor to check for a 0 ohm reading..there are 3 leads so you will have to test all 3 in all combinations possible...for example: the 3 leads of a transistor are labled E,B,C...so you want to test E and B, E and C, B and C...if you find a shorted transistor, then you will need to get the part number off the transistor and obtain replacements...you can order replacements at mcmelectronics.com

Mar 03, 2011 | Audio Players & Recorders

1 Answer

toshiba 37av635DB,no display.fuse check:ok,lead: ok there was lightning and thunder.could possibly cut off one of the transistor. what could really happen?


very possible. look for punched through transistors, open 0 ohm resistors (they use them as fuses), open surface mount fuses (the flat green ones), other surface mount fuses (small rectangular white box looking things) and bulging/leaking electrolytic capacitors.
Remember that if you find what appears to be a shorted transistor, to remove it from the circuit and re-test it. Sometimes a transistor will be across a coil, and therefore read shorted.
look at any 120lead postage stamp sized ICs to see if they cracked their tops.

Chances are you'll find a fuse and a transistor and maybe a couple caps that need replacing.

TIP: when checking transistors, To remove them from the circuit I find it's easiest to simply clip 2 of the 3 leads, test, and solder the lead back together if it's ok. If it's bad, I clip the third lead, and then desolder each leg individually...much less effort and time that way!

Mar 02, 2011 | Televison & Video

2 Answers

Blown fuse everytime it powers on


yes right there is a short circuit in power supply if you are non technical then replace the power supply if you are technical then open the power supply and check the 4diodes of bridge if faulty replace it again check transistor attatched to heat sink if faulty repalce it

Feb 28, 2010 | Pyramid (PS36KX) 600-Watt Power Supply

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