SIEG KX-1 KX-2 parallel interface board repair/replacement suggestions

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mgbyrne3

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I have a KX-1 CNC mini mill sold by Little Machine Shop that has lost three direction motor output channels. Pins are stuck active low regardless of commanded direction. Losses occurred incrementally over a couple of weeks and my work around was to reassign spare output pins via Mach3.

With recent history I'm out spare pins and considering replacing the interface board. The installed OEM board is labeled Mach SM-11 on the schematic and on the board.

Options:

1) repair: one candidate fault is failed optical isolators on affected channels. I'm not confident of my ability to confirm that nor identify and install replacements.

2) Little Machine Shop parts for KX-1 shows interface boards for over $500. I assume these were production OEM.

3) Alibaba.com offers what appears to be OEM boards for around $300 (if I can only one?).

4) cnc4pc.com offers C11G boards for under $100. My OEM technical documentation shows the KX1 mill cabinet with that label on the parallel interface board. I'm guessing this was a pre production board installation.

I would appreciate feedback regarding repair or replacement of the KX-1interface board:

1) board troubleshooting and repair experience?

2) experience with the vendors I've mentioned or other candidate sources?

3) Experience with current production C11R board? Data sheet inspection suggests C11G is pin compatible but the relay output connections for motor speed control are not obvious to me.


I would appreciate any help from KX1/KX3 users.

Mike
 

timo_gross

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  • any pictures of the thing? Parallel Interface Board, 3501 & 3503 3721 - LittleMachineShop.com that one?
  • do you have any idea why your I/O failed? If you spend 500$ on a sparepart keeping the root cause "functional" it will damage the new part as it did damage the old one. :cool:
  • Are you sure it is the interface card? Maybe it is your PC that does the bad stuff?
  • I think if you pay for the spare part (as always) you do not pay for the board, you pay storage, documentation, drop in compatibility, saving your nerves and time wasted.
Greetings Timo
 

mgbyrne3

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Thanks,

Board looks like the one for Vx1/KX3 you mentioned. LMS parts pictures match the installed board.

I have 2 different computers both running with Mach 3 via integrated motherboard parallel adapters. Adapter issue seems less likely.

I don't know why the IO ports failed. In each case the direction channel failed active high for a short intermittent period.
It would work, go down, recover after an overnight shutdown, then a hard failure. Workshop was not hot cabinet cover is off.

I agree with you notions of spare pricing. I trying to do due diligence.
 

timo_gross

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Thanks,

Board looks like the one for Vx1/KX3 you mentioned. LMS parts pictures match the installed board.

I have 2 different computers both running with Mach 3 via integrated motherboard parallel adapters. Adapter issue seems less likely.

I don't know why the IO ports failed. In each case the direction channel failed active high for a short intermittent period.
It would work, go down, recover after an overnight shutdown, then a hard failure. Workshop was not hot cabinet cover is off.

I agree with you notions of spare pricing. I trying to do due diligence.
Just another odd thought, I had also a non working machine last week. Yesterday I got around to have a look and I noticed that one of the stepper drivers was defective. As a result none of the three axis was moving.
 

mgbyrne3

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I currently have bi directional motion on 3 axis. With the failed high direction signal, jog in both directions results in same direction offset. Reassigning motor drive output to a spare pin restores bi direction control.

Al 4 of my motor drivers seem to be working; I swapped Z to the spare and saw no change until I also reassigned the pin.
 

RonGinger

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I have re-wired a couple of the KX1 machines to use one of the common parallel port breakout boards. I have used both PMDX boards and CNC4PC boards. Either work fine. Just remove the current board and mount the new one in its place, then rewire to the current steppers.

The spindle speed control is a bit harder to get right, but most of the BOBs offer an analog voltage output.

I did one using the CNC4PC board with the daughter card for a Smoothstepper and ran Mach4.
 

bdrmachine

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That board looks fairly straight forward to repair if you have a hot air soldering station. They are pretty cheap these days. Try doing a search on LinuxCNC as there maybe some folks that have tackled this issue before.

When it comes to troubleshooting you have the advantage that their are multiple circuits to compare against.

$500+ sure seems like a HUGE makeup on such a simple board with such a small part count.
 
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That looks like a very typical optically isolated parallel break out board. Unfortunately LMS doesn't have docs for the board showing. You'll have to go back into the machine or the documentation with the machine to double check there aren't any weird functions, and what kind of spindle control is used. As Ron mentioned, the spindle control can be a bit interesting. As this is a basic machine using mostly standard parts, odds are pages 6 and 7 of the C11G users manual will fill in the blanks for VFD or PWM. I'd suggest figuring out exactly what you really have and if there is a reason it failed. Double checking voltages would be a good idea before proceeding further. If nothing turns up, don't spend sleepless nights searching, quite a few of the Chinese chips have a shorter lifespan that you might expect compared to US and Taiwan chip fab houses. They are getting better every year, magic smoke blowing out prematurely is a far less frequent event these days, although leaving protective diodes out of 5A stepper drivers still occurs...

Note that the board you have is optoisolated, while the C11G is buffered. Probably of no significance for most folks, but can be useful if you have to float the lines off ground.

Good luck sorting it out,
Stan
 
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