I have tried to search through existing questions to find an answer to my question, but so far have had no luck. I apologize (and feel free to flag) if this is a dupe.

I am working on repairing an arcade monitor, and I think that one of the transistors on the neck board is bad. I have removed the transistor, and am trying to test it with my multimeter. The transistor is a C3229, and the datasheet is here: http://www.datasheetcafe.com/c3229-datasheet-transistor/

According to the datasheet, it is an NPN transistor and the pins are (1)Base, (2)Collector, (3)Emitter. I am trying to determine if this transistor is bad, but I'm getting confused. Here are the readings I get in diode mode:

  • (+)->(-)
  • B->C: 0.647V
  • B->E: 0.666V

and in ohms mode (20M):

  • (+)->(-)
  • B->C: 13.05M
  • B->E: ----

ohms mode (200M):

  • (+)->(-)
  • B->C: 1.1M
  • B->E: 1.2M

And I do not get any readings if I reverse the probes. I had assumed that this transistor was bad, but it is possible that it was just a loose solder joint. Is it possible to tell from my readings whether the transistor is bad, or is there something else I can test to find out if it is bad? Also, is there a good place to find new transistors? My searching thus far has turned up a few sites that look promising, but none that carry this particular transistor so far.


I tested a couple other of the same transistor which I am pretty sure are not bad, and got very similar readings. I will assume that the problem was not the transistor.


1 Answer 1


C3229 transistor testing.

Your voltages sound ok, but resistance of a transistor pn or np junction is non ohmic. ie changes according to the voltage across it. I'd look for other problems. I don't think replacing with another transistor would yield different result.

  • \$\begingroup\$ I agree. My other transistors have very similar readings. There is a diode that is on the same circuit (red color drive) that is backwards from the other (green and blue) colors. Some images I see on Google show the diodes the same way I have mine installed, with the red appearing backwards. Could a reversed diode cause issues? \$\endgroup\$
    – dub stylee
    Aug 2, 2017 at 3:27
  • \$\begingroup\$ uk.farnell.com/nte-electronics/nte2501/… \$\endgroup\$
    – user158592
    Aug 2, 2017 at 3:30
  • \$\begingroup\$ prev/next window had tweet length capability, so heres the link for your device, Farnell are an excellent company. uk.farnell.com/nte-electronics/nte2501/… \$\endgroup\$
    – user158592
    Aug 2, 2017 at 3:46
  • \$\begingroup\$ FARNELL This company have an exellent reputation, and an equivalent of your device,in case you need difficult to find stuff in future. Check the dc bias WHEN IN CIRCUIT and switched on, would be in region of 0.6 volts. dry joints/resistor burn/overcurrent from previous or later stages. Google for cct diags of product with working test voltages ??? ps diodes are polarity sensitive, reversing would lead to total malfunction/burnout/random symptoms good luck use google more . its very clever! \$\endgroup\$
    – user158592
    Aug 2, 2017 at 3:47
  • \$\begingroup\$ I will check out Farnell. Yes, I've definitely been googling a lot! As far as the polarity, I'm not sure if it is backwards or not. I have found images of the same board with the same diode backwards from the other two like mine. Also found images of the opposite. Trying to find what it is supposed to be :p \$\endgroup\$
    – dub stylee
    Aug 2, 2017 at 3:50

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