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IndustryArena Forum > MetalWorking Machines > Tormach Personal CNC Mill > Anyone had a control board failure?
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  1. #1
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    Anyone had a control board failure?

    Just trying to troubleshoot a problem with my Series III.
    When I switch on power to the secondary control circuit it trips out the MCB/breaker every time. Primary power circuit is fine.
    After some rudimentary tracing today, if I remove 230V power to the control board (wire#202 to J5-2 on the machine control board) then the tripping stops. Plug it back in and it trips. Mostly immediate, but occasionally takes a second or so.

    I've stopped checking for today (I'm in the UK and it's cold, dark, and haunted out there now), but first thoughts seem to be a control board failure of one component or another. I'm not an electronics guy in the slightest, so excuse my broad description.

    But just wondering if anyone else has had a control board failure, and if so, what were the symptoms? Or is there something else simple I should go and check tomorrow?
    I'll say thank you in advance for any help or insight provided

  2. #2

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    Re: Anyone had a control board failure?

    I don't know the series 3 at all but looking at the wiring diagram it appears that 202 runs through a 6 amp fuse and continues on to provide power to the coolant, computer and computer monitor outlets on the machine. Do those outlets function correctly?

  3. #3
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    Re: Anyone had a control board failure?

    Quote Originally Posted by soofle616 View Post
    I don't know the series 3 at all but looking at the wiring diagram it appears that 202 runs through a 6 amp fuse and continues on to provide power to the coolant, computer and computer monitor outlets on the machine. Do those outlets function correctly?
    Though a process of disconnecting at various points and testing - then yes, up to that point nothing is producing a dead short to trip the mcb.
    So it's either the board or something else connecting through/past the control board. I was hoping someone else may have experienced a similar issue and would have some insight.

  4. #4
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    Re: Anyone had a control board failure?

    Their wiring diagram is confusing, but wire 202 sure looks like it's on a 110v circuit. If you're feeding it 220v that is a problem.

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    Re: Anyone had a control board failure?

    Quote Originally Posted by footpetaljones View Post
    Their wiring diagram is confusing, but wire 202 sure looks like it's on a 110v circuit. If you're feeding it 220v that is a problem.
    It comes straight off the 230V line via the main disconnect then line 207 and FU6. We don't use 110v here in the UK except via stepdown transformers where required - and obviously Tormach confirmed this voltage was perfectly OK before I bought the mill 9 yrs ago. It's been running flawlessly since then, so supply voltage is not the issue. A dead short somewhere is.

  6. #6
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    Re: Anyone had a control board failure?

    Quote Originally Posted by Peter Neill View Post
    It comes straight off the 230V line via the main disconnect then line 207 and FU6. We don't use 110v here in the UK except via stepdown transformers where required - and obviously Tormach confirmed this voltage was perfectly OK before I bought the mill 9 yrs ago. It's been running flawlessly since then, so supply voltage is not the issue. A dead short somewhere is.
    Hi Peter
    As you say, 230V is ok.
    Just for the record, does your fuse trip when you turn on the main disconnect or only after you press the green button on the control panel?
    Can you identify whether the fuse is tripping due to an overload or does the FI trip due to an earth leakage current?

    J5-1 and J5-2 only connect to the fuse F2 and the normally open contacts of the relay K5. That's exactly what I would expect, and I can see no other tracks on the board. If you disconnect J5-2 you should measure an open circuit between these two terminals. The contacts close when PathPilot turns on the coolant and this requires the mill to be fully powered.
    Even if these contacts are shorted this should only turn on the coolant pump, or what ever you have connected to this outlet.

    Presumably you've tried pulling all the plugs on this circuit and inserting them one by one? First the input power, then coolant output, PC and finally monitor?
    Have you tested with just the coolant switch set to "off"?

    Do you have ANYTHING else connected to this mains circuit in the house/workshop? If so, it would be worth pulling the plugs (not just turning them off). It may be due to a completely unrelated device. You mention "I'm in the UK and it's cold, dark, and haunted out there now" (that's one of the reasons I left the UK ) - perhaps you're using some form of electrical heating in the workshop that you don't normally have???

    Let us know how you're getting on.
    Step

  7. #7
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    I've got a thread posted here on my problem this past Fall. Summarizing, I cooked the coolant pump which blew a fuse. The steppers could be powered up, but the PathPilot controller and monitor were dead.

    I pulled the PP and monitor plugs and ran them to a separate plug to get back up and running. That's when I found that the pump was fried. Replaced the pump and fuse and was back up running.

    Maybe try the same thing, run the PP computer and monitor on a remote plug.

    Bruce

  8. #8
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    Re: Anyone had a control board failure?

    Removed and isolated wire #204 & 207 from J5-1 and J5-2 on the controller board, everything fires up perfectly, and no tripping.
    I still have the coolant pump working and delivering pressure just fine, but only via the manual switch on the cabinet, rather than through software or machine control.
    Been test running the machine thorough some warmup programs for a couple of hours and all seems fine.

    I'm going to check the pump out separately over the next few days as I need to do a coolant change. But I'm sure it's ok, as it's still going through the original supply circuit, and any earth faults or shorts would trip the mcb immediately.
    So it looks like the fault is either in the connections to the board or to/in the K5 relay

  9. #9
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    Re: Anyone had a control board failure?

    Quote Originally Posted by Peter Neill View Post
    Removed and isolated wire #204 & 207 from J5-1 and J5-2 on the controller board, everything fires up perfectly, and no tripping.
    I still have the coolant pump working and delivering pressure just fine, but only via the manual switch on the cabinet, rather than through software or machine control.
    Been test running the machine thorough some warmup programs for a couple of hours and all seems fine.

    I'm going to check the pump out separately over the next few days as I need to do a coolant change. But I'm sure it's ok, as it's still going through the original supply circuit, and any earth faults or shorts would trip the mcb immediately.
    So it looks like the fault is either in the connections to the board or to/in the K5 relay
    A relay "shouldn't" really short from the coil to the contacts but anything's possible. You may also have a small leakage current. With J5-1 and J5-2 disconnected check the resistance from the test pin TP3 (red arrow) to the two terminals J5-1 and J5-2. The measurements should show an open circuit.
    Step

    Attachment 455516

  10. #10
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    Re: Anyone had a control board failure?

    Yep, open circuit with no continuity between the test pin or either junction.
    Did find a couple of millivolts there though.

  11. #11
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    Re: Anyone had a control board failure?

    Quote Originally Posted by Peter Neill View Post
    Yep, open circuit with no continuity between the test pin or either junction.
    Did find a couple of millivolts there though.
    I disconnected J5-1 and J5-2 on my machine and my DMM showed less than 0.2mV, which is too small to be relied on. I checked out the board again and I can really only see connections from these two terminals to the fuse and relay contacts. However improbable I can only assume there is a small leakage current either through the relay or between the PCB tracks.
    Attachment 455638
    A new board costs a small fortune. The relays are fairly standard and cost maybe £2 but they would be difficult to remove without damaging the board. My approach would be to first try adding another relay on the output of the board so the wires 202 and 205 connect only to the output terminals of the new relay and the on-board relay only drives the coil of the new relay. The coil could be driven from a small isolated power supply, like a 12V wall socket "brick". The new relay would provide the isolation - if this is indeed the issue - so any leakage paths on the board would become irrelevant. I would also tie the 0V of the 12V circuit to chassis to prevent it drifting.
    First we would need to make sure the on-board relay is still working and being driven by the driver IC (U9 - to the left of the Power and Probe LEDs). I'd recommend attaching a couple of wires to J5-1 and J5-2 to bring the connections away from dangerous voltages. You can then safely measure the continuity while switching the coolant relay on and off using the PathPilot Coolant button. If PathPilot can control the relay, and the relay contacts still switch, then the above solution should work ok.
    Step

  12. #12
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    Re: Anyone had a control board failure?

    Another test option would be to replace the coolant pump with another load (say a desk lamp)
    If the lamp works, the most likely culprit is the coolant pump motor. Its _very_ unlikely that
    a relay would have a coil/contact short (at least without some fireworks)

  13. #13
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    Re: Anyone had a control board failure?

    Quote Originally Posted by PCW_MESA View Post
    Another test option would be to replace the coolant pump with another load (say a desk lamp)
    If the lamp works, the most likely culprit is the coolant pump motor. Its _very_ unlikely that
    a relay would have a coil/contact short (at least without some fireworks)
    As I said earlier "A relay "shouldn't" really short from the coil to the contacts", that's why I had Peter measure the continuity and he confirmed "...open circuit with no continuity between the test pin or either junction." so we're not talking about a short at this point. Peter also mentioned that after inserting the wires into the terminals it sometimes "takes a second or so" for the circuit to trip. The pump runs fine via the manual switch and the on-board relay is simply connected in parallel to this switch. If everything on the board were ok, simply connecting the terminals would have zero affect on the operation. However, connecting the wires to the terminals trips the breaker. So based on this information I'm assuming the failure mode must be associated in some way with this path. The only other failure mode I can imagine, however improbable, would be a leakage current from the live connection (which would be wire 202) either via the relay contacts across to the coil, or perhaps more likely between two tracks on the board, through to the control circuitry, which may trip an earth leakage switch (I think you might call them RCDs?). This leakage path would hardly be measurable with DMM voltages. I had originally suspected the culprit would be either the PC or pump but Peters' measurements appear to contradict this. The machine is 9 years old so an increased leakage current, however improbable, is not absolutely impossible.

    When you have eliminated the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes).

    Step

  14. #14
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    Re: Anyone had a control board failure?

    Appreciate your help on this TurboStep. My electrical/electronics knowledge is definitely in the limited category.
    I've got a project machining some A2 steel that I need to get on with, and I'll be doing that dry, with carbide & an air blast. And when that's done I'll, follow your further testing advice.
    For the moment it's just good to be able to use the machine again

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