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  1. #31
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    Quote Originally Posted by Bob Willson View Post
    My thanks to everyone who has kept this thread going. I wasn't able to reply because of the flooding. I only just got power back at 1 am last night.

    I have some things to do, but soon as I can I will take off the IGBT and measure it again and replace it if necessary.
    Hi Bob. Just noticed where you live. Did you cop it very bad? (I used to live in Goodna, glad I don't any more.)

    I was battening down the hatches ready for when it hit the Illawarra, but we were lucky and it fizzled out early.

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  3. #32
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    Hi Humphrey

    No, I was OK. I didn't really expect to go under again, because I live half way up a slope which raises me about 2 metres from the poor buggers below me.
    As it turned out, the water heights in Brisbane were not as bad as had been predicted. Unlike Bundaberg which is really copping it hard.

    Really all that happened to me is that I lost power and internet for a few days and I think that I only lost those because SEQEB was playing it safe.
    Bob Willson
    The term 'grammar nazi' was invented to make people, who don't know their grammar, feel OK about being uneducated.

  4. #33
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    Quote Originally Posted by Bob Willson View Post
    Hi Humphrey

    No, I was OK. I didn't really expect to go under again, because I live half way up a slope which raises me about 2 metres from the poor buggers below me.
    As it turned out, the water heights in Brisbane were not as bad as had been predicted. Unlike Bundaberg which is really copping it hard.

    Really all that happened to me is that I lost power and internet for a few days and I think that I only lost those because SEQEB was playing it safe.
    Good to hear. My brother lives in Brisbane, too, but wasn't seriously affected.

  5. #34
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    OK, I have removed and measured the resistance of the IGBT.

    G - C ∞
    G - E ∞
    C - E 3M8
    Bob Willson
    The term 'grammar nazi' was invented to make people, who don't know their grammar, feel OK about being uneducated.

  6. #35
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    G'day Bob

    If you have a diode test on your multi-meter you're probably better off using that.
    Do the same tests on diode setting, and each time, swap the two leads around - so, first off red to C, black to E then black to C, red to E, etc, etc...
    As a final comparison, check the readings against another IGBT, or maybe two. They should be approximately the same readings.

  7. #36
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    Tester set for diodes.
    With the positive lead to the emitter and the black lead to the collector I get a reading of 0.425. No other leads give any signal at all.
    The other transistors give the following readings in circuit.

    Q17: E - C = ∞, C - G = 0.431 E - G = 1.7 to 1.9
    Q18: E - C = 1.4, C - G = 0.431 E - G = 1.7 to 1.9
    Q19: E - C = 1.084, C - G = 0.000 E - G = 1.7 to 1.9
    Q20: E - C = 0.425, C - G = ∞ E - G = ∞
    Q21: E - C = ∞, C - G = 0.431 E - G = 1.7 to 1.9
    Q22: E - C = 1.4, C - G = 0.431 E - G = 1.7 to 1.9

    The E-G readings were very similar in all cases as also were the C - G
    Q19 has two anomalies.
    I hope that I didn't stuff up any measurements, it all gets a little confusing after a while.
    Bob Willson
    The term 'grammar nazi' was invented to make people, who don't know their grammar, feel OK about being uneducated.

  8. #37
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    Quote Originally Posted by Bob Willson View Post
    OK, I have removed and measured the resistance of the IGBT.

    G - C ∞
    G - E ∞
    C - E 3M8
    Hmm. No C-E short there, now.
    Measure between the C and E pads on the PCB, where the IGBT came from.

  9. #38
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    Quote Originally Posted by Bob Willson View Post
    Tester set for diodes.
    With the positive lead to the emitter and the black lead to the collector I get a reading of 0.425. No other leads give any signal at all.
    The other transistors give the following readings in circuit.

    Q17: E - C = ∞, C - G = 0.431 E - G = 1.7 to 1.9
    Q18: E - C = 1.4, C - G = 0.431 E - G = 1.7 to 1.9
    Q19: E - C = 1.084, C - G = 0.000 E - G = 1.7 to 1.9
    Q20: E - C = 0.425, C - G = ∞ E - G = ∞
    Q21: E - C = ∞, C - G = 0.431 E - G = 1.7 to 1.9
    Q22: E - C = 1.4, C - G = 0.431 E - G = 1.7 to 1.9

    The E-G readings were very similar in all cases as also were the C - G
    Q19 has two anomalies.
    I hope that I didn't stuff up any measurements, it all gets a little confusing after a while.
    With an IGBT, due to the insulated gate, a diode test will only be able to measure the internal diode, E-C, but any measurements to the gate will be infinite. 0.43V is about right for the diode, I'd say.

  10. #39
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    Bob, I remember you saying that the supplier would replace that unit, but that you'd have to pay $35 postage. Returning it is really the best option. Unless you don't have to return this one to them, in which case you could end up with two.

  11. #40
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    Quote Originally Posted by Bob Willson View Post
    Tester set for diodes.
    With the positive lead to the emitter and the black lead to the collector I get a reading of 0.425. No other leads give any signal at all.
    That's about what I'd expect for a forward biased diode, unless you get the same reading with the leads swapped over.
    The 1.7 to 1.8 on the G-E would be the path of the 10k resistors and zeners.
    It's a bit odd that now the 0 reading is on the G-C of Q19, unless it's the opto driver at fault - PC2?

  12. #41
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    Quote Originally Posted by Humphrey9999 View Post
    Hmm. No C-E short there, now.
    Measure between the C and E pads on the PCB, where the IGBT came from.
    C - E 3M3 resistance both ways (+ and -)
    C - E diode tester: 0.487 with + to E and - to C
    Bob Willson
    The term 'grammar nazi' was invented to make people, who don't know their grammar, feel OK about being uneducated.

  13. #42
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    Quote Originally Posted by Humphrey9999 View Post
    Bob, I remember you saying that the supplier would replace that unit, but that you'd have to pay $35 postage. Returning it is really the best option. Unless you don't have to return this one to them, in which case you could end up with two.
    No, what I said was that they are supplying me with a new one, but that it cost me an extra $35 postage. This saves me returning the old one to China. BUT I would like to be able to fix this one so that I then have a spare. .. Quite apart from that, I hate throwing away something that may be able to be fixed relatively easily.
    Bob Willson
    The term 'grammar nazi' was invented to make people, who don't know their grammar, feel OK about being uneducated.

  14. #43
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    Quote Originally Posted by Bob Willson View Post
    No, what I said was that they are supplying me with a new one, but that it cost me an extra $35 postage. This saves me returning the old one to China. BUT I would like to be able to fix this one so that I then have a spare. .. Quite apart from that, I hate throwing away something that may be able to be fixed relatively easily.
    Right. Fair enough.

    In that case, if all else fails, the other option is to wait for the new one to arrive, then do comparative measurements between equivalent points on both.

    Did you measure between the C-E pads on the PCB, with the IGBT removed? That C-E short that you measured must be there, since the IGBT itself isn't shorted, unless there was previously a solder bridge across the pins on the PCB causing the problem.

  15. #44
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    Quote Originally Posted by Bob Willson View Post
    C - E 3M3 resistance both ways (+ and -)
    C - E diode tester: 0.487 with + to E and - to C
    These aren't with the IGBT removed, are they? This is getting confusing.

  16. #45
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    G'day all,

    I've just stripped my drive down so I could give it a good blow out to get rid of the layers of MDF dust in it. While it was apart, I took a few measurements and noted down the results.
    The red line in the picture is the red lead of the DMM, the blue is the black lead. GCE markings are from the datasheet specs. The resistance readings were typical of all IGBT's, no matter which way the leads were put on the pads.
    All readings were an in circuit test on a Fluke 189 DMM
    Attached Images Attached Images

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