Can somebody help me to test these transistors... - Page 1
Forum section: electronics / beginners

author: kasumyku
author_rank: Regular Contributor
timestamp: April 10, 2013, 06:19:31 pm
content: Hello everyone,I have pulled these two transistors out of a 5.1 channel receiver , which I'm suspecting them being bad but don't really know how to test them. I know that either PNP or NPN from emitter to collector current can't pass either way, and on both of them current does pass from E to C, but maybe i don't know how to test them.Can anyone please let me know how to test them on Diode mode.I have attached both data sheets.Thanks!

author: olsenn
author_rank: Frequent Contributor
timestamp: April 10, 2013, 06:42:39 pm
content: In both NPN and PNP transistors, current flow between the collector and emitter. If a high voltage level on the base-emitter junction is required to allow current to from from C to E, then it is an NPN. If a low voltage on the base-emitter junction is required for current to flow then it is a PNP.

author: kasumyku
author_rank: Regular Contributor
timestamp: April 10, 2013, 06:48:10 pm
content: thanks for reply, but how test them on Diode mode to see if they are bad?

author: w2aew
author_rank: Super Contributor
timestamp: April 10, 2013, 07:01:34 pm
content: C to E should show open in either direction.You can treat the B-E and B-C as diodes. The should conduct in one direction, and not the other (like a diode).

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 10, 2013, 07:03:23 pm
content: Lets see if I can get it correct .Most transistors are partially made up of a diode , some go in , some go out - base & emitter .Using a multi meter on a resistance setting check for 0 ohms , or continuity , in one direction and then the other , never good if continuity in same in both directions .Or search on youtube ,https://www.youtube.com/results?search_query=testing+transistors+with+multimeter&oq=testing+tra&gs_l=youtube.1.0.0l10.16779.22704.0.30405.13.12.1.0.0.0.105.887.11j1.12.0...0.0...1ac.1.YwWrlkSG74M

author: kasumyku
author_rank: Regular Contributor
timestamp: April 10, 2013, 07:38:27 pm
content: I found out that these are Darlington transistors, 2 transistors in 1 .So the current amplified by the first is amplified further by the second transistor.Some of them have resistors inside between Base and Emitter, also a separate diode between Emitter and Collector.But after all I still don't know how to test them.Thanks for the the videos and links guys but unfortunately those testings are for regular BJT Transistors with only a single transistor inside.

author: SeanB
author_rank: Super Contributor
timestamp: April 10, 2013, 08:07:17 pm
content: Simplest way is to connect them up in a simple circuit as a DC amplifier, and measure the conditions. A power rail of around 12V, a 100R 1W resistor to the collector and a 10k resistor between collector and base with emitter to ground will enable you to measure both base voltage, collector voltage and se that it does have gain. Collector voltage will be something below the supply, but not 0V ( then it is short) while base will be at around 0.6V to 1V. For the PNP the supply to collector will be negative, but voltages will be similar in magnitude.

author: kasumyku
author_rank: Regular Contributor
timestamp: April 10, 2013, 08:34:08 pm
content: Hello Sean,I know it may sound simple to you but for a super newbie like me its like a different languagewhich I'm learning little by little every day.My question are:Does this technique applies to Darlington Transistors?Please clarify what you mean by "with emitter to ground " ?Also "a 100R 1W resistor to the collector " to the collector from where?So, regarding testing, between which pins do I have check voltage?Thank you!

author: Nickk2057
author_rank: Regular Contributor
timestamp: April 11, 2013, 02:36:21 am
content: ok... i might be able to help clearify this..... i used transistors to help with my inverter circuit before (which was ones from an old hi power amplifire) the ones you said was NPN and PNP... but to be sure of this is to try it this way... if you have a PC fan (which is low on amps and won't hurt the transistors) you can hook up the fan on the positive of the battery and the negitive on the right side of the NPN type transistors and hook up the negitive part of the battery on the center and use a wire with a resistor on it and touch the base (which is the one on the left if you looking at the front of the transistor)... if it is a PNP transistor then switch the polarity around on the collector (which is the center) and the emmiter (which is the right one)hope this works out for you

author: Nickk2057
author_rank: Regular Contributor
timestamp: April 11, 2013, 02:39:49 am
content: also i might add that when you touch the base to the collector it will make the fan come on... and when you disconnect the base to the collector it will turn off the fan

author: c4757p
author_rank: Super Contributor
timestamp: April 11, 2013, 02:52:27 am
content: Quote from: Nickk2057 on April 11, 2013, 02:36:21 am1) Those are BCE, not BEC. Fan goes to the center terminal.2) Dude, just draw it.3) Negative. Emitter.4) Don't do this. The inductive spike when the fan shuts off can damage the transistor. Use a non-reactive load like an LED with a resistor, or a small 12V lamp.

author: Nickk2057
author_rank: Regular Contributor
timestamp: April 11, 2013, 02:57:31 am
content: i guess i need to work on it too... but it did work on my end... oh well... back to work i guess XD