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Thread: DM4400-what size 3 phase motor for rotary converter

  1. #21
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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Okay then, that blew the fuse again right away. I guess the problem lies elsewhere.



  2. #22
    Community Moderator Jim Dawson's Avatar
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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Try disconnecting the armature wires at the drive. That will eliminate any cabling from there to the motor.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Okay, sorry to be thick about this--I can follow a recipe pretty well and stay safe around electricity, but not sure about that one. Looking at the manual, on page 8 there are 4 heavy gauge wires at the upper right on the drive board itself. On page 15, terminal TB202 the three heavy wires at the top show as input. I'm assuming the armature wires are the former, and not the latter?



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Never mind, I found it on the machine schematics--it is the two left wires at the upper right from the amp manual on page 8. Those two wires go to terminal 4 and 5 on TB202.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    And the same result, fuse blows after about 5 seconds. 3 down, 2 to go before heading to Lowe's for another pack of fuses.



  6. #26
    Community Moderator Jim Dawson's Avatar
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    Default Re: DM4400-what size 3 phase motor for rotary converter

    This is not a good sign. I think that means that the output section is somehow shorted to ground, not totally sure about this. Normally a ground fault occurs at the motor, not in the drive itself. Was this machine running when you bought it?



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    No it was not, although they assured me it was--the only reason they de-commisioned it was because the oiler had stopped working causing a fault on the X stepper. I have fixed the oiler and everything is now working but the spindle.

    About that, I just did a cursory exam of the board and found something that doesn't look right and may be easily repaired. On the upper left (page 8) there are six test points. All of the test points are bent over and shorting out on each other. That can't be right, so I am going to bend them back away from each other. I'll let you know the results soon.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Bent all the pins away from each other and re-assembled with high hopes. No such luck. I have the board out again and made some continuity checks on all the test pins and found that pin 1 is still shorted to pin 2. In the Dyna troubleshooting manual they refer to these test pins for making adjustments to the amp using pots on the board, so I did some more careful checking on what they do. I found that pin 1 is definitely connected to ground--I could not find a diagram or reference in the manual anywhere, but I followed the trace on the board and it definitely connects with some large ground plane areas on the board, so I feel pretty sure that it's supposed to be grounded. However, pin 2 is referred to in the manual as an adjustment for something using the Aux pot, so I don't think that's supposed to be grounded normally. What do you think?



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    I found the answer about TP2 from the troubleshooter--it says to "measure from TP2 to ground and adjust Aux pot CCW....", so definitely not supposed to be grounded. I gained access to the back of the board by removing a large heat sink while I plugged in my de-soldering iron. I'm going to temporarily remove pin 2 from the board and go from there.



  10. #30
    Community Moderator Jim Dawson's Avatar
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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Test point 2 (TP2) goes to ground through the Aux pot, R27. See page 29 (of 31), Top left (ish) corner. So it should not read 0 ohms unless the pot is turned all the way CCW



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    Community Moderator Jim Dawson's Avatar
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    Default Re: DM4400-what size 3 phase motor for rotary converter

    If you look at the lower right of the schematic on page 29, it shows the ground fault system. The output section is completely transformer isolated from the rest of the electronics on the board. I would be taking a hard look at the filter cap, C 70. In fact, I would be looking at the other 4 caps in that area also. That would be the logical failure point. Next would be a shorted output transistor.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    If my current route leads nowhere I'll take a look at that. I did check the pot and it was certainly not all the way CCW (I marked it and turned it one full turn CCW and it still wasn't stopping, then turned it back) and the resistance between TP2 and ground was absolutely 0, so it seems likely to me that's where the problem is. I removed the pin but it's still grounding so not sure where the problem is. I'm going to try using an exacto knife to cut all around the solder pad on pin 2 except for the trace to the pot and see what that does. Since all the pins were bent over it appears some kind of abuse happened there so I'm concentrating my efforts there for now.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Well that's gotten me nowhere. I know next to nothing about electronics, so all I can do is follow your advice about C70. I don't see a value for it on the schematic, and there's no value visible on the capacitor itself. Can you tell what the value is supposed to be? Also, does it need to be removed from the board (isolated) to get the correct value with a meter?



  14. #34
    Community Moderator Jim Dawson's Avatar
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    Default Re: DM4400-what size 3 phase motor for rotary converter

    I can't see a value on the schematic, but put the ohmmeter probes across the cap and it might start out at near 0 ohms, and then climb as the cap charges. If it stays at 0 then the cap might be shorted.

    I just noticed, there is no bleeder resistor on the DC bus, check for voltage across that cap before checking across it for a short.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    I tested it several times and always got the same result--after about 10 seconds it settles at 0.540 M ohms. Well, enough for today. I got two of these from the same place and the other one in storage was making parts when I bought it--I'm going to stop in tomorrow and pull the amp from that and try it in this machine. I want to get to the point of using it on single phase, one of my original goals, and if I can get there then I'll deal with the bad amp later. Thanks Jim

    Dan



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    That is the reading I would expect, so all seems OK there. Sounds like a plan, I'll be around and happy to help if I can.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Hey Jim-

    I talked with Marty this morning and he provided this link as a troubleshooting possibility:

    http://www.cnczone.com/forums/servo-...servo-amp.html

    I'll be taking a look at this soon. It's not the exact same amp but close enough. I'll keep you posted.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Hi Jim-

    So yesterday afternoon I spent some time with the advice from the previous link, but I didn't get any where with that. I studied the board carefully with a magnifier, but nothing jumped out at me and I didn't quite understand how to make the checks described (geez I wish I was better with electronics). I wasn't about to take it apart to check for physical shorts, all those big transistors (I think) and the heat sink would have been a nightmare and I surely would have brought the whole project to an end then and there, so I fiddled around a little more with the bent test point area just to feel like I was accomplishing something. I decided to check the resistance at TP2 just to see what it had been set to but then remembered it was 0, so I decided to play with the adjustment on the aux pot it was connected with, but no matter where I set it the resistance was always 0. I went one step further and de-soldered the pot just to check it out isolated from the board--I got 19.something K across one set of legs (don't remember what I got across the other two sets, I think it was infinite or 0 on one set and the same 19K across the third set). I then turned the adjustment knob and checked, but the resistance never changed. I thought I must be doing something wrong, so I removed another pot just to see. I then got readings that made sense--about 20K across the outer legs, and 2 different values across the other two sets that were roughly additive to 20K, and I could get various values while adjusting it. So my conclusion was that the pot for TP2 must not be any good. With the pot removed I went back to TP2 to check resistance to ground--I don't recall what the value was (back to work today) but it was definitely not 0 anymore, nor was it infinite. I was not able to interpret the diagram to deduce what it might have been without going through the pot, so my only conclusion from that whole exercise was that the pot had gone bad. I'd be shocked if I had more or less stumbled on the problem, but I'd appreciate your comments on my efforts so far.

    Today I plan to order some new pots, plus a rectifier (while I'm ordering electronics anyway) so I can replace the seemingly bad pot and have the rectifier on hand for the 3 phase to single phase conversion when (if) I get the board back to working order. I also plan to give Servo Dynamics tech support a call soon to see if they can offer any guidance.



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Call Servo Dynamics support. As I mentioned to you in a precious email, this fault seems common on these amps. Hopefully SD support can offer some guidance. These is a fellow on YouTube that worked with an SD 3060. Search it and read the comments. Simply a lead. I would replace the 3 phase power diode bridge with a square package bridge needs to be done anyway. Keep us posted.
    Marty



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    Default Re: DM4400-what size 3 phase motor for rotary converter

    Marty-

    I need to replace that pot (43P203) so I'd like to order that from the same place as the rectifier, but I'm having trouble finding both items in one place. Got any suggestions? If I have to I can split it up, but I know I'll pay a lot more in shipping that way.



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DM4400-what size 3 phase motor for rotary converter

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