Problem DC Servo and Amp Repair


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Thread: DC Servo and Amp Repair

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    Default DC Servo and Amp Repair

    I'm back for more Knowledge from the Fadal experts! Does anyone have a part number for the power transistors on a Glentek Amp -0008.This is a DC Amp from a 93 model 6030. The old transistors have a Glentek part number, GTK 45705. Nothing comes up on a google search. I called Glentek,and with much begging ,the tech told me it was a IGBT with 600v 50A rating. But wouldnt tell a standard part number. He did say that they have a new Transistor upgrade,part number GTK 45763. and the cost was 70.00 each!!!!! and he had 1000 in stock. There is 12 transistors on the board. I know that they can be found at mouser or digikey or somewhere for 4.00 to 8.00 ! Finances dictate trying to fix it till I can replace the amp with a new one. These old boards have very basic components,and most of them are user repairable, for a very modest price. The root cause of the board failure, was a carbon tracked set of brush holders, from years of poor maintanence and coolant ingression. TIA.

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    Community Moderator Al_The_Man's Avatar
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    Default

    They could be similar that is used by Westamp, which were the same vintage and similar design.
    These replacements were MJ11032 and if the complement is needed, MJ11033.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default

    Thanks for the reply Al. The transistor you pointed out is a darlington. With the case form TO-204 ( I think ).My IGBT form is a TO-247. With the single mount hole. I appreciate your quick reply. Maybe if we figure this out we can save fellow Fadal users some hard earned cash. Dwayne



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    Exclamation GTK stuff

    Hi !

    I did some research in this part. It is a FET so not really a "normal" transistor.

    It has a supressor diode inside between Drain-Source (collector-emmiter).

    You should look for a FET with paramaters (ratings) : 600 Vmax D-S and Imax 50 A.

    Of course a speedy FET is required for this application.

    Packing : To-3P if im right.

    So the housing is plastic. Backplate is metal.

    Akos

    Last edited by pilot001; 05-28-2012 at 07:24 AM.
    FADAL VMC4020 HT 1995, Z 28" (if true) , 88HS , 10K rmp , 21 TC geneva /rotary/ , VH-65 (A-axis) ,3ph 400V , metric, NO conveyor, No palette. (+alternative DC AMP)


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    Exclamation gtk

    HI !

    So....

    Those AMPs which are equipped with 12 power FETs can use of course a weaker Amper rated FET since 3 is paralell connected , so all pins are common (gate, drain , source). So max 20 amper flows through 3fets at the same time. Voltage still the same of course. So a fet can be used radted only for 10 as well and it still can handle more than 20A.

    DC servo AMP card revision C , D probably got 12 FETs , later they changed it to less (8 FET). Or those with less are rated for less Amper.

    Akos

    FADAL VMC4020 HT 1995, Z 28" (if true) , 88HS , 10K rmp , 21 TC geneva /rotary/ , VH-65 (A-axis) ,3ph 400V , metric, NO conveyor, No palette. (+alternative DC AMP)


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    Exclamation succesful repair

    Hi !

    I think ive managed to repair my DC servo AMP.

    Problem was that it made the axis go further than it was programmed. AMP was used for Z axis so it was watchable as it ran over and "bounced" back to its desired position. It was of course mostly recognisable when it was stopping form G0. And made error : ' AMP error '

    Ive changed 2 ICs and ALL trasistors and FETs (not the power FETs). The two IC was the I/O ic-thats a schmitt trigger ic- and one operational amplifier next to the O/I ic.

    So i put it into X axis today for testing. Made the balancing procedure and now i can not see this overshooting. I even raised the MAX feed from 400 to 700 IMP.
    It was lowered cose this error what Z axis made with the faulty AMP card.

    Made som tests high speed , low speed, circular iterpolations etc. NO error occurred.

    I hope thats all for me.

    FADAL VMC4020 HT 1995, Z 28" (if true) , 88HS , 10K rmp , 21 TC geneva /rotary/ , VH-65 (A-axis) ,3ph 400V , metric, NO conveyor, No palette. (+alternative DC AMP)


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    Default repairing



    Ive made some works on the same panel cose it started to behave as before. Made AMP FAULT on screen. So i replaced all ICs on the panel. But that was a bit complicated.

    There is a OPTO coupler for the power FETs (4pcs 6pin ICs next to the FETs). And there are 3 FET drivers. 4 is needed, but each driver has 2 circuit inside so they made it so. (Every circuit drives 3 FET so 4*3=12 fet is used). In the middle all is used at the sides only one driver circuit is used. Driver makes an inverted signal cose power FETs are N channel fets so they "open" to a negative voltage.

    This 3 diver IC is a SG3626. Has 8 "leg" and it is next to the FETs as well. This one i ve tried to replace but it was a mistake. Probably this SG3626 is a bit different form what i tried. It blown ot some power FETs along whit the 20A fuse. LOL

    So i put back the SG3626. And the optos too. All other IC has been replaced with new ones.

    Power FET what i used to replace the GTK45705 --- IRFP460 (N channel FET, 500V / 20A) ( TO247 )

    Picture is before the FET replacement... RED-opto couplers, Yellow-FET drivers



    This means the nearly only one FET could do the work of the 3, but to cope with the loads and temps 2 or 3 is better to have.


    Akos

    Last edited by pilot001; 07-20-2012 at 04:54 PM.
    FADAL VMC4020 HT 1995, Z 28" (if true) , 88HS , 10K rmp , 21 TC geneva /rotary/ , VH-65 (A-axis) ,3ph 400V , metric, NO conveyor, No palette. (+alternative DC AMP)


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    Default Re: repairing

    Would you please share what type opto-couplers are suitable for this application. On my board (GA370) two GTK45708 are burned. Drivers are SG3626 too, but now these parts are not available and I have to replace them with some other types.
    Thank you.



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    Member pilot001's Avatar
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    Lightbulb Re: repairing

    Hi !

    I cant give u a brand nor a part number.... sorry (i have no access to the board)

    As for the opto coupler. Should be the same pinout and a fast one (or not too slow) * response time,
    The controller side is not really problematic.... the conrolled side should be 300 V rated at least... but i guess those can take pretty more..

    Of course u can use a diffrent pinout version but the u need a "stick on" board there.

    Akos.

    FADAL VMC4020 HT 1995, Z 28" (if true) , 88HS , 10K rmp , 21 TC geneva /rotary/ , VH-65 (A-axis) ,3ph 400V , metric, NO conveyor, No palette. (+alternative DC AMP)


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    Default Re: repairing

    Thanks for the reply.
    After reading your posts above I left with the impression that you have replaced all ICs except opto-couplers and drivers. And transistors, of course. Am I right?



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