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Haas Brushed Servo AMP repair

STJ7780

Cast Iron
Joined
Jul 9, 2009
Location
Dallas, Ga
Well I have looked all over and I have not come up with any solid info on repairing the servo drive boards for the older Haas brush style servo motors. I have 2 bad drive cards and it kills me to look at them and know that all of the components on the boards are easily replaced. If I could figure out what went bad, I could have a good working servo amp again for a fraction of a new or rebuilt card would cost me. So I thought I would start a thread on testing and repair of the Haas Servo AMP card. Try to gather collective information in an effort to find a fix for all of us. I am competent enough to test and solder on new components but the theory behind how the cards actually work is where I am in the dark.

So far on both my boards I have not burned or discolored areas. No burned smell or any other indication of irreparable damage. Both cards set servo overload alarms but the axis themselves were not overloaded and moved freely. Long story short, new card, axis works.

My gut reaction was to point the finger at the MOSFET transistors but they "look" OK and are difficult to test. The original style of mount transistor does not exist any more. But new ones do in the same electrical configuration so if they were bad, then new mounts and heat sinks would need to be made. Part# IXFH50N20-ND. Best I can tell, the controls command movement, the amp commands the servo on and looks for the encoder to show movement. When the encoder does not show movement, the alarm sets.

I have also come across a mention of the opto-isolator going out on these boards, but I am not sure how to test these.

Here are a few pictures of the boards I have.
2012-03-18212726.jpg

2012-03-18212940.jpg


Steve
 
I am going to combine information that I get from other sources to try and help find a solution. Below is what some others have come up with so far.

Most all those i've seen are in sockets, even though it may not look like it at first.

Digi-Key - IXFM24N50-ND (Manufacturer - IXFM24N50)

Check against the data sheet
http://ixdev.ixys.com/DataSheet/91522.pdf

I have not tried to remove the MOSFETs yet but that makes more sense on the mounting. That will make them a lot easier to test and replace. :D
The link to DigiKey is for the correct mount but the amperage and voltage are different. 24A vs 50A and 500V vs 200V. Are MOSFETs like capacitors where they do not have to be exactly the same to work? I tried to find a comparable MOSFET but no luck. I am probably not looking in the right place.
Here are the 2 data sheets so everyone can compare;

This is for the original part number;
Manufacturer: IXYS
Product Category: MOSFET
RoHS: RoHS Compliant Details
Transistor Polarity: N-Channel
Drain-Source Breakdown Voltage: 200 V
Gate-Source Breakdown Voltage: +/- 20 V
Continuous Drain Current: 50 A
Resistance Drain-Source RDS (on): 0.045 Ohms
Configuration: Single
Maximum Operating Temperature: + 150 C
Mounting Style: Through Hole
Package / Case: TO-204AE
Packaging: Tube
Fall Time: 16 ns
Forward Transconductance gFS (Max / Min): 32 s
Minimum Operating Temperature: - 55 C
Power Dissipation: 300 W
Rise Time: 15 ns
Factory Pack Quantity: 20
Typical Turn-Off Delay Time: 72 ns

This is the part number referenced above;
Family FETs - Single
Series HiPerFET™
FET Type MOSFET N-Channel, Metal Oxide
FET Feature Standard
Drain to Source Voltage (Vdss) 500V
Current - Continuous Drain (Id) @ 25° C 24A
Rds On (Max) @ Id, Vgs 230 mOhm @ 500mA, 10V
Vgs(th) (Max) @ Id 4V @ 4mA
Gate Charge (Qg) @ Vgs 160nC @ 10V
Input Capacitance (Ciss) @ Vds 4200pF @ 25V
Power - Max 300W
Mounting Type Chassis Mount
Package / Case TO-204AA, TO-3
Supplier Device Package TO-204AA
Packaging Tube

The Mosfets should be quite easy to test. Should just have to remove the screws and pull them out.
Usually when MOSFETs go bad they short out. So to test them you can use an ohmmeter to check the resistance between the pins and also between each pin and the case (assuming the case is electrically connected). If you get zero resistance (dead short) between any two points the part is dead. Replacing any dead MOSFETs may bring it back to life, but then maybe not as there could be other components that went bad and killed the MOSFETs.

C|

Thanks for the tips on checking the MOSFET. My meter is at work and I am off today so I will give it a shot tomorrow and post the results.
What could cause the MOSFETs to go bad? I know that shorted or bad cables and motor problems can kill the drive but is there any thing on the board itself that can cause it?

Thanks for the input guys, hopefully we can figure this out and save us Haas guys some dough!

Steve
 
I have a some more to share about the dead drives.

I started to check over everything and I tested the transistors but I came up with nothing. Then I saw a bad solder connection for the main 160VDC power feed to one of the boards. This is the board that would alarm instantly when I powered on the servos. I am assuming that the 160VDC was not even making it to the rest of the board and hence setting the alarm. I am going to have to de-solder it, clean it and re-solder it back on and test it. I tried to just re-solder it but it has oxidized too bad to take the solder. I will post the results when I have them.

2012-03-31182410.jpg


I am also bringing this over form another site, it is some very good information on how the boards function.
Being a DC drive this is going to be an H-Bridge configuration, If one side is on or firing and the other side turns on, it creates a dead short across the supply through two adjacent devices, sometimes this can occur if one side of the drive is on and a power supply is switch off for any reason, this can turn the opposite side on as the HV decays and blow the HEXFETS, one protection for this can be to fit high sweep rectifier fuses in the H bridge feed.
This used to be the norm in SCR drive packages to protect very expensive drive components.
Al.

I am still trying to learn how they work. It makes diagnostics a lot easier if you know how the component operates. :cool: This is why I started this thread, to hopefully get a collective of information for the good of all. :D Thanks :cheers:

Steve
 
That is an amazingly simple drive!

I am an electronics guy, but I have no experience with with Haas drives, although I have lots of experience with motion control in general.

Are you sure those FET's are no longer made in that package? That is a standard TO-3 package. If that specific one is not available, you should be able to get something equal or better for not too much money.

Your solder joints definitely look bad - should be a quick fix, but solder joints don't tend to go cold... they either started that way or they didn't.

Opto isolator should be simple to test with appropriate equipment. It's basically just a light activated switch in a chip. Put power in (current regulated), see if the output switches. If so, it's good, otherwise it's bad.

I fixed a few drives before and in most cases it's been the transistors/FETs. Those TO-3's shouldn't be too expensive, especially for a brushed DC motor drive, so if it were me I'd fix the cold solder joints then probably just swap out the FETs. You can test them, but you can't test them easily under full load or even drive load, so they can test OK and still fail when in use.

They could be blown out from the issue you mentioned, but I tend to doubt it....
 
I know this thread is a little old...but did you ever figure out the problem and/or where to get the parts? I think I have an A axis card that is out and I'd like to repair it (instead of replacing) if I can.
 
1992 VF0, brushed servos.
In short, It seems my X axis servo drive is damaged. Started with X axis over current alarm. I repaired a damaged motor lead at connector. Evidence of corrosion and bad repair. Brush and commutator clean,lead screw/thrust bearings all good. Fuses all check out. Cable buzzes good, no shorts or breaks.

Still alarms at power up but at at least now makes partial rotation bump when pressing reset.

After reading all I could find I have some questions.

I have a fourth axis drive card - can I simply swap that card run the axis, I have seen yes and no.. ??

This repair shown - I can do that, seems to be worth the trouble, yes?

Finally, anyone have a schematic, I have experts to consult and bench test but they need a schematic. Can anyone provide one.

Apologies if I missed answers to my questions - not lazy, I just have so little time and I am near desperate.
Thanks.
 
Measuring the commutator with an Ohm meter may not show shorts in the motor wires. Carbon build-up in the windings can short at 160V but show none at meter levels. When you have the motor apart you should wash the armature down with alcohol standing it on end.
A fourth axis card can be used but they have less current capacity than the XYZ. Do not push it to high speeds and it will work fine.
What I have seen is usually one or two of the output IGBTs short and also takes out the drive resistors and transistors, usually R72, R70, T11, T3.
Once the 12 volt regulator IC46 was burned out and a trace from the sense resistor opened.
Differences between versions is mostly the output transistors and drive resistors, the number of diodes and filter capacitor values for the low voltage supplies.
Attached is a bitmap of the components.
PM will not let me upload the schematic of adequate size to be readable. Send me your E-mail address.
Servo_Board_Rev_K.jpg
 
The 4th axis card turned out to be for axis drive only and working fine now. What a relief!
In box refreshed - Thanks again!
 
Curious if anyone has the schematic for this card? Would be grateful if you could send it my way.
 
There are some differences depending upon the version. This is the K:
 

Attachments

  • PN_32-4070_Rev_K.jpg
    PN_32-4070_Rev_K.jpg
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E-mail sent with schematics and encoder wiring. By the by, your message box is full.

Curious if this thread is still alive, that last picture of the schematics is pretty fuzzy. Hoping to get a better image or other format, maybe by email?

Trying to diagnose a code 104 "X Servo Error Too Large", replaced the X board with the A board for the time being but this seems to be a persistent problem with three of our machines and I don't want to spend 700 dollars every time we replace a card.
 
I am interested too. My old VF3 is working fine for now, but you never know.
Any documents that exist would be nice to have on standby. Same with machine firmware and load procedures..I wonder if there are any copies out in the wild.


Well, actually I guess the machine isnt flawless. I do get offset CRC errors on every power up but thats just it forgetting that the macro variables are all zero since I dont have macros, or g52 X goes to an absurdly large value. Not the end of the world, easy to Id and correct.

And occasionally Z faults out on rapid moves.

Old machine problems, hah.
 
E-mail is probably the best, I do not get on here regularly. I have a couple different versions of the brushed servo board schematic. Mostly the changes are the diodes for the power supply, the output transistors and a few associated parts.
When the output transistors go out they usually take out a few of the gate circuit components. The obsolete output transistors can be found in the surplus market.
Alarm 104 is the Y axis, not X axis.
 
Normally you can get rid of the CRC errors by simply turn off setting 7. Go into you parameters. Pick any 1 ( write down its value) chit the estop. Change its value to something else. Then remove e stop. Reset control. Then hit e stop again. Change the value back on the parameter you had changed previously. And most of the time the CRC error will go away . What happens is the sum of the combined parameters equals a value it doesn't like. By changing the value, you force the control to re equate the values.
 
I know this thread is a bit dated. I am also interested in any documents that exist in regards to the drives. Thanks In advance.
 
this is the best image I have of the schematic. I've ended up just replacing the parts labeled on the attached photo

Servo_Board_Rev_K.jpg



PN_32-4070_Rev_K_2.jpg


Can anyone take a photo of the servo drive power board? I have a resistor (R7) that is not identifiable.
WIN_20200616_12_09_18_Pro.jpg

Thanks:)
 








 
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