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Testing a NPN Darlington Transistor

I'm testing a NPN Darlington transistor to see if it is OK. Transistor is for an electronic ignition system on an ATV. Transistor marking ETD41-035. I'm using a Fluke 179 true RMS meter on the diode test setting. Here are the readings I'm getting.

B-C: .543 vdc
B-E: .639 vdc
C-B: infinite
E-B: 1.54 vdc

So going by the test procedure I should be seeing infinite E-B correct?
 
The readings would be consistent with a functional Darlington that has bias resistors and a CE protection diode. Random example (2SD2014):
Darlington.png
 
Unfortunately I can not find the datasheet or any information. Just found a thread on another forum in which the gentlemen stated the same, but was given an alternative transistor to replace with. The replacement worked in his case, and was also being used in an electronic ignition system.
 
Personally I think the ECM is fine. I helped my cousin troubleshoot a similar problem with his ATV and it turned out to be the stator. This one was removed by a colleague and handed to me to try and fix. I can't find anything wrong with it.
 
ADRT,
good find,but...
In this case your original darlington can actually be good.
Best thing would be to build a simple test circuit for it .
like this:
closing the switch should light the led(a 20ma led) .

Voltages on the darlington should be about:
VCE=0.9V
VBE=1.4V

Darlington tester.jpg
 
ModemHead said that there is a reverse diode.

My bad, I used weasel words (like a politician) "is consistent with".

Strictly speaking, no E-C measurement was included, and even if there was, with bias resistors, a diode, and the B-C junction, there would be two current paths from E to C, so it would be hard to *absolutely* confirm the presence of the diode.
 
My bad, I used weasel words (like a politician) "is consistent with".

Strictly speaking, no E-C measurement was included, and even if there was, with bias resistors, a diode, and the B-C junction, there would be two current paths from E to C, so it would be hard to *absolutely* confirm the presence of the diode.
I was going to add that a C-E test in both directions was a good idea.

And note my weasel-words- I didn't say "there is a reverse diode". Instead I quoted you. :D
 
ModemHead,
You are correct ,there is no C-E measurement!
I jumped to the conclusion(Freudian?) that the "infinity" was of E-C :oops:.

ADRT,
can you please test the E-C bidirectionally and post?
 
Thinking further (a sometimes dangerous thing), if the diode is *not* present, an E-C diode-test reading should be above the reasonable range for a diode forward voltage, due to the bias resistor drop in addition to the B-C junction drop. (A Fluke 179, like many DMMs, uses an approximate 1mA test current.) So a "reasonable" diode forward voltage reading in the E-C direction should confirm the diode is there.
 
ADRT,
good find,but...
In this case your original darlington can actually be good.
Best thing would be to build a simple test circuit for it .
like this:
closing the switch should light the led(a 20ma led) .

Voltages on the darlington should be about:
VCE=0.9V
VBE=1.4V

View attachment 22229
I'm going to try this test circuit this evening just to cover all my bases. Personally I hate working on the components of a machine without actually testing it in place myself. I think he has other problems.
 
So tested this in circuit and it tested fine. Talked to the gentleman about it and sure enough he actually didn't check the stator coils as I suspected. Thanks for all the help guys. :)
 
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