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2016-12-30

How to test Panasonic plasma TV IGBT transistors - GT30F131 and similar, RJP30H2A, DG302

In Panasonic Plasma TVs the Y-Sus (aka SC/SN) and Z-Sus (aka SS) boards contain a number of high current, high voltage IGBT transistors of different types. Those are not easy to test, because they are hybrids. They have a MOSFET gate, but a bipolar emitter and collector.

The usual FET testing technique is to pre-charge the gate, not touch it again and then measure the source-drain resistance, which must be low with a charged gate. That doesn't work with IGBTs. Neither does the classic bipolar testing method work.

To properly test IGBTs, we need a test fixture. This circuit simply applies a variable voltage to the gate and the emitter-collector current goes through a resistor. We measure the gate voltage and the E-C current.


This battery-driven version is good for quick testing. To make comparisons between different devices and to put some stress on them, use a lab supply and decrease the collector resistor.


To test the SMD IGBTs I quickly solder the gate and the emitter to the board. The collector is connected to the tab and a gentle push on top of the device connects it to the large pad.


Now let's check the three types.

The 30F131 starts opening at slightly under 4V GE (gate-emitter) voltage. It is open at 5V.





The DG302 starts opening just above 5V, it is open at about 5.8V.




The RJP30H2A starts opening at about 4.2V and is open at 5V.




As you can already see, those IGBTs have quite different characteristics.

I spent a considerable time studying the offers on Aliexpress. Some were easily detectable as fakes. When the character font used for labeling is obviously wrong, the numbers are not engraved into the casing or the stamp in the center is missing or different, it must be fake. The pictures of the seller I ordered from seemed ok. Either they were more careful faking it or I get lucky :-)

I have a pending delivery of the 30F131 and RJP from China. I am going to check against fake devices with this test technique. The tests above have been conducted with original parts. I always keep some originals as a reference.

Update: Fake IGBTs

The RJP from China are obviously fake. Neither do the look the same, nor do they measure like the original. I will not bother using them to avoid further damage to the board.

Don't buy them from "Chinese Super Electronic market". I recon, to get originals you will have to spend a few dollars per piece.

The F131 don't look the same, but they behaved ok in the measurements. I am still not confident to use them.

I also ordered the driver transistors (SMD 3Y) and the control chip from that seller. I'll test those later.

I've put the fake transistors under the microscope. Please see this blog post.

C-E Reverse Break-Through Voltage Test

Another very revealing test is to measure the reverse break-through voltage between emitter and collector. I use my DUOYI DY294 tester for this.
  • The orginial RJP has 230V. The chinese fake only 45V(!!). I'll dump that garbage right into the trash.
  • The original F131 has 110V, so does the chinese. Maybe those are not so fake.
  • The original RF1501 diode has 375V, the chinese is right on the spot. Forward voltage is identical, too. So, those are most likely legit. They also look absolutely identical.

RF1501 diode is ok


In the meantime I fixed another 50GT30 with one of the RF diodes and they are working flawlessly. I can recommend the source for those.
https://www.aliexpress.com/item/10PCS-RF1501-RF1501NS3S-TO-263/32515394351.html

15 comments:

  1. Great post! Im pretty sure you will get fake 30F131/RJP30H2A from China. All my boards blew up using those fake igbt's. Instead i now use FGD4536TM for a substitute of both parts. I got them from Ebay ( user monitor-09 ). Boards are running much cooler with these parts and they are very reliable. ( also much smaller ).

    You ever had blowing diodes above the white prong connector? It happens with fake parts.

    thanks , Mark

    ReplyDelete
    Replies
    1. Thanks Mark, rest assured that I will put the chinese pills under stress before I solder them in. I am not too optimistic. It's an experiment.

      I know a trustworthy source (transistormosfet.com), where one piece costs 3$. Those must be genuine.

      As a backup I also ordered a larger batch of FGD from DigiKey after I had read a lot about them on Badcaps. Those are also discontinued (Mouser doesn't have them anymore) and I think it is wise to stock up. As plasma TVs are not manufactured anymore, those parts will all die out sooner or later.

      So far, the diodes at the top were not shot on the boards I have fixed.

      I'm going to share my experiences in the blog.

      Delete
    2. Yeah, I've been screwed. The IGBTs are fakes. Measurably and visually. I'll go with the FGD.

      Delete
    3. Hello. In my case i can't tell anything wrong about chips i recieved from aliexpress.
      I have repaired 50GT30 and 42GT30 with chinese components from the first attempt (i just followed your article about repairing 50GT30 and 42ST30), step by step (i used Lukey 868 station, no pre-heat or something)
      I'm not electronic engineer and english is not my native language.
      Can you explain what is "break-through voltage", how can i mesure it?
      And final questions:
      whether the Y-SUS board will work if replacement RJP30 like yours have 45V break-through voltage, or they MUST blown without any chance? I want to understand... If my TVs are working does it means that RJP30 i recieved is good? Or the may suddenly blow?

      Delete
    4. Hi,
      the break-through voltage tells you the amount of voltage that is necessary to let a certain amount of current flow (a few milliamps). A diode has a forward voltage of 0.7V for example. Zener diodes have a specific reverse break through voltage. For IGBTs, this is actually not a relevant parameter as such, but it tells you whether the devices are built the same when you compare an original to others.
      To test it you need special testers like the DUOYI.

      I did not say that all Chinese suppliers have fakes. I reported my experiences with one specific supplier. It is like finding a needle in a haystack. If your TVs work, you had luck, I guess. From what I have heard, fake IGBTs blow up very soon. I did not trust my chineses IGBTs, there were too many signs of fake.

      Delete
    5. Ok. Thanks for explaining.
      42GT30 works about a month now. I hope for long life after repair =))
      I'll tell if anything goes wrong.

      Delete
  2. Thanks for the quick response! I really like your blog. No the blown parts ( 2 diodes and 2 resistors ) only happen when you use fake parts. Hope the parts are fine , if so then i will order them also from that site. Keep up the good work.

    ReplyDelete
  3. Hello Hermann,

    Could you possibly help me with a problem with a Panasonic tx-p50gt30e?
    Thanks in advance

    ReplyDelete
    Replies
    1. Have you read my repair story, yet?
      http://alpengeist-tvrepair.blogspot.com/2015/05/panasonic-tx-p50gt30e-once-more-7-blink.html

      That's all I know about this plasma model.

      Delete
  4. HEllo,
    I bought a new Rf1501 diode and I can't figure out if its a good one.
    Testing in diode mode with a multimeter, it seems to let the current pass in a way and the other....

    ReplyDelete
    Replies
    1. You gave the answer yourself. A diode which is conducting in both directions is broken.

      Delete
  5. Hi Hermann

    When using your DY294 to test IGBT devices for Vbr did you make sure to short the gate to the emitter? I found I did not get reliable results with my tester unless I did so.

    The manual shows normal bipolar devices with the base left unconnected for Vbr but for FETs the gate is shorted to source. There is no mention of IGBT devices.

    I nearly threw out an order of parts from a Chinese supplier that actually test ok.

    Andy

    ReplyDelete
    Replies
    1. Interesting! I did not do that. IGBTs are both, FETs and bipolar, thus I had no idea whether they need special treatment. I just compared them to my original good reference part and assumed that all others must measure the same. I could imagine that you might have had residual charge on the gates after some previous measurements.

      It does make sense to lock the gate by pulling it to minus, though. Thank you for this observation!

      Delete
  6. I tested a batch of Chinese DG302s against some original salvaged parts and they mostly seemed ok with the gate floating but as you found in previous tests the have a slightly higher threshold.

    I then tested a batch of Chinese RJP30H2s, which I was initially disappointed to find under 20V until I shorted the gate to emitter. They all went up to around 400V after that.

    The supplier I use has generally been very good and the only parts I've had blow up were some FGD4536s, which they refunded me for in full.

    ReplyDelete
  7. hi... help dg501lw same number

    ReplyDelete

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