Is there a test procedure for DK-463 ICs (TR8-L Servo Drive / TR43B top board)
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    Default Is there a test procedure for DK-463 ICs (TR8-L Servo Drive / TR43B top board)

    I have an alarm "2 - excess servo lag Z" when attempting to move +Z direction.

    I believe I've narrowed the problem down to the top board.

    There are 8 test pins at the top-right corner of the top-board that represent the voltage to the large transistor modules in the drive. Each of these pins allows checking of the signal down to the transistor modules in the drive.

    One of these base signals 2B2 (channel 2 is Z axis) is not firing. The voltage stays at a negative value when attempting to move the Z axis in either direction.

    At this point, I believe the problem is a bad DK-463 module for that particular channel. Is there any way to check for a dead DK-463 module using a quality DMM? In circuit, or on the bench?

    I'll order some spare DK chips, but I'd like to know if that's really the issue before I stop investigating.

    Thanks for any and all help and suggestions guys.

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    The hybrid DK chips are a common failure point on Mitsubishi drives, so more-than-likely that's your issue.

    I don't know of any way to test the DK's, other than comparative testing against a known-good one.

    MEAU usually won't sell the DK chips, but I have sourced them on eBay.

    MEAU will usually replace associated caps (and resistors/diodes?) when they replace a DK chip.

    Good luck with it, and keep us posted.

    ToolCat

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    Quote Originally Posted by cnctoolcat View Post
    The hybrid DK chips are a common failure point on Mitsubishi drives, so more-than-likely that's your issue.

    I don't know of any way to test the DK's, other than comparative testing against a known-good one.

    MEAU usually won't sell the DK chips, but I have sourced them on eBay.

    MEAU will usually replace associated caps (and resistors/diodes?) when they replace a DK chip.

    Good luck with it, and keep us posted.

    ToolCat

    Thanks, good to know the e-bay ones are ok, I ordered 5 of them last night.

    Hearing that they're a common failure point is reassuring.
    Since I'm getting signal on 7 out of 8 channels (all four in X and 3 of 4 in Z) I had to assume they were the culprit.
    I checked all the other components on that driver section of the board and they seem to be in good shape.

    I may pick up a good/used top-board if I can find one soon.
    I'll repair the old one and have the spare on the shelf.

    I checked all the caps on the board, they are not bulged and seem well within spec, but I'll probably get with one of the electronics parts dealers and get those caps on the way too.

    The board has definitely been reworked at some point, but by someone with good soldering skills.
    All the DK chips appear to have been replaced, maybe the caps too.

    I found a PDF for the drive, that helped confirm that I was on the right track too.
    If someone else needs a copy let me know.

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    For proper testing of those DK hybrids You will not get away only with DMM. At least good signal generator, laboratory power supply and oscilloscope is needed. Thats about it. The price for those obsolete and crappy DK's are awful. All they contain is some cheap optocoupler (not in all of DK series), couple of resistors, capacitors and few transistors. Thats why I replaced all burned out driver stage for braking part in FREQROL FR-SF with self designed circuit. This is not a space technology, and by using modern chips and other components is possible to get the same (or even better) results.

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    Quote Originally Posted by GuntisK View Post
    For proper testing of those DK hybrids You will not get away only with DMM. At least good signal generator, laboratory power supply and oscilloscope is needed. Thats about it. The price for those obsolete and crappy DK's are awful. All they contain is some cheap optocoupler (not in all of DK series), couple of resistors, capacitors and few transistors. Thats why I replaced all burned out driver stage for braking part in FREQROL FR-SF with self designed circuit. This is not a space technology, and by using modern chips and other components is possible to get the same (or even better) results.
    Do you have a schematic for the DK's or for your home-brew circuit?
    I'm fairly savvy with electronics and will probably try to de-cap one of these DK-463's after my machine is repaired.

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    Quote Originally Posted by cwtoyota View Post
    Do you have a schematic for the DK's or for your home-brew circuit?
    I'm fairly savvy with electronics and will probably try to de-cap one of these DK-463's after my machine is repaired.
    I got circuit only for DK434 that is used in FREQROL FR-SE VFD. These epoxy encapsulated modules seems to be of the same secret level like Area 51. Basically they all are the same- some just contains optocoupler like mentioned DK434 or DK463 in Your drive, or without it- like DK456 in FR-SF. In attachments there is some interesting photos with DK434 replacement- and its just a bunch of cheap SMd parts there. Also I have attached circuit of driver I used for FR-SF repair (VFD of my MAZAK had completely burned out half of the firing circuit, also PCB traces were damaged). The only easy way to go was using popular HCPL-3120 IGBT driver chip with additional power stage for reliable opening and closing of IGBT. I made all 6 channels with through hole components and placed the PCB (size 120*54mm) on the side of VFD and connected to main control board with wires. Maybe one day will redesign everything with SMD parts to shrink the size of driver board. But for now it works very well. dk434circuit.jpg
    Attached Thumbnails Attached Thumbnails firingcircuitigbt.jpg   dk434-.jpg   dk434.jpg  

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    Quote Originally Posted by GuntisK View Post
    I got circuit only for DK434 that is used in FREQROL FR-SE VFD. These epoxy encapsulated modules seems to be of the same secret level like Area 51. Basically they all are the same- some just contains optocoupler like mentioned DK434 or DK463 in Your drive, or without it- like DK456 in FR-SF. In attachments there is some interesting photos with DK434 replacement- and its just a bunch of cheap SMd parts there. Also I have attached circuit of driver I used for FR-SF repair (VFD of my MAZAK had completely burned out half of the firing circuit, also PCB traces were damaged). The only easy way to go was using popular HCPL-3120 IGBT driver chip with additional power stage for reliable opening and closing of IGBT. I made all 6 channels with through hole components and placed the PCB (size 120*54mm) on the side of VFD and connected to main control board with wires. Maybe one day will redesign everything with SMD parts to shrink the size of driver board. But for now it works very well. dk434circuit.jpg
    Thanks! I appreciate the diagrams.

    That's a fairly simple circuit and board to make. There is a high quality board fab shop about 3 hours south of me, I'll probably do a little work on this just for fun when I have some free time. I'll post some photos and hopefully a rough schematic of the DK-463 when I get the epoxy off of it.

    Area 51 secrecy on an inexpensive part that is easily replaced and inexpensive to build... I am usually a skeptic when people claim "engineered to fail", but parts like these DK modules sure bring a good case for it. I'm sure there have been many millions of dollars made replacing these simple modules over the past 30-something years.

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    I have heard that epoxy used in electronics softens a bit after holding module in solvent (acetone and similar). I dissected one DK456 just for fun by heating it with heat gun. Epoxy then cracks and while it is soft You can remove it by scalpel or any other tool.
    You are abolutely right about all that money involved in this. Its not a first time I see that such simple things are being kept as a big secret. But for a keen enthusiast only principle of working is needed to get the things working right.
    cwtoyota- did You check the servo power supply? Because very often burnt driver IC make some damage in power supply- it can be diode or capacitor.

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    Quote Originally Posted by GuntisK View Post
    I have heard that epoxy used in electronics softens a bit after holding module in solvent (acetone and similar). I dissected one DK456 just for fun by heating it with heat gun. Epoxy then cracks and while it is soft You can remove it by scalpel or any other tool.
    You are abolutely right about all that money involved in this. Its not a first time I see that such simple things are being kept as a big secret. But for a keen enthusiast only principle of working is needed to get the things working right.
    cwtoyota- did You check the servo power supply? Because very often burnt driver IC make some damage in power supply- it can be diode or capacitor.
    I'm 99% sure the power supply is fine. The X axis runs on the same amp and it is 100% working. The Z axis works only in one direction. The top-board is not sending any signal down to one of the large transistor modules, so it has to be the DK chip or part of the driver circuit. I checked the transistor and all the passive components in the driver section and they all seem to be in spec.

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    Quote Originally Posted by cwtoyota View Post
    I'm 99% sure the power supply is fine. The X axis runs on the same amp and it is 100% working. The Z axis works only in one direction. The top-board is not sending any signal down to one of the large transistor modules, so it has to be the DK chip or part of the driver circuit. I checked the transistor and all the passive components in the driver section and they all seem to be in spec.

    Risky business is to replace these IGBT drivers with home made stuff. Mitsubishi made a good driver years ago, and if they fail, then there is reason for it. Best way to replace them would be using something made by INTERNATIONAL RECTIFIER company as they focused on power electronics, or download CAD Simulator, create a circuit and simulate it on your PC. In that case you can create an equivalent of IGBT gate load and see how fast your design can discharge it and charge it. If rising and falling times are very good ( what is most important factor when operating IGBT bridge) then you build it. Otherwise it is too risky.

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    Quote Originally Posted by noname777 View Post
    Risky business is to replace these IGBT drivers with home made stuff. Mitsubishi made a good driver years ago, and if they fail, then there is reason for it.
    There is really no space high-tech in those older Mitsubishi IGBT drivers. There is a couple reasons why they die- bad power supply, bad IGBT due to aging. Basically thats all. It is possible to make very good DIY IGBT driver to replace DK (circuit that I posted works in my Mazak with very good results). But with one note- there should be at least some experience in power electronics...

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    good point. But I see no connection in between bad power supply and aging IGBT. IGBT is going bad itself that is alright with me, but drivers job is charge/discharge Gate input capacity, which is primary load for driver. That is why modeling is good, you can actually create very hard conditions and simulate supply voltage drop and huge load capacity, to see if driver survives.

    Bad power supply, well ..DC voltage goes down, so driver pulls more DC current. I seen heaps of these DK replaced, but still puzzled why they die. Honestly.

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    Actually there is connection between both power supply and aging IGBT, but even that's not all (these two are typical problems). IGBT is just like tyres for Your car- it has some resource, different working modes affect it. There is many other factors we should take into consideration. For example- what is the operating mode of VFD where another IGBT or driver burnt down? I'm certain sure (I give 99% on that) guys here that encountered this problem- their ramping up/down speed was set too high. These are the most critical modes in VFD work. At certain occasions driver can be killed by commutation overvoltage coming through IGBT gate pin (imagine capacitor that is discharged through driver circuit). Even copper bus bars thats connected to IGBT power terminals can create headaches- these bars have inductivity. Therefore all energy stored in that inductivity (its really small) creates fast overload (timing is in nano and microseconds). Usually IGBT can withstand such fast overloads, but then there comes that one day... Some of You may have seen these red capacitors on IGBT terminals- they are used to supress slow overvoltages that come from power line. And these are just a bit of all problems. Power electronic is very interesting area- thats for sure.

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