THC Troubleshooting (No resistance)

That seems about right. Are you getting voltage out of the div output cable from the VIM? It should be around 1.5v

measured it and got -2.3V with the red inside the barrel and black outside of the barrel.

Per the THC troubleshooting guide- The DC voltage that you measure here should be identical to the value measured in step 1 above. If you are getting a negative voltage here but the magnitude of this value is correct, you need to switch the polarity of your wiring on the plug to the 50:1 voltage port. Failure to do so will result in no voltage reading in FireControl; the THC module can only measure positive voltage.

Is this my issue? If so, how do I switch the polarity of the wiring on the plug?

If you measure directly on the pins in the connector on the front of the plasma cutter, the red should be on the right and the black should be on the left. If you get negative voltage there, the wires on the back of the connector are reversed.

If you get positive there, but negative at the other end of the cable, then the cable is wired incorrectly to the aviation connector.

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so it is 2.6V on the pins in the connector on the front of the plasma cutter (red on right and black on left).

As tested previously, I measured -2.3V on the div output cable from the VIM (red inside barrel and black measuring outside the barrel).

so with what you stated previously, the cable is wired incorrectly to the aviation connector? Could you explain that further or how I might fix that issue. Also, would this issue cause the THC problem?

If you are getting negative voltage out of the VIM, that will definitely cause a zero voltage reading on the THC.

You should be getting a lower voltage out of the DIV output from the VIM, since the VIM lowers the out from 50:1 to 73:1.

Measure the output at the barrel connector end of the Divided voltage cable that is connected to the plasma cutter(meaning before it goes into the VIM). Red on the inside and black on the outside. Is that voltage negative?

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Yes, that one is negative.

Also measured -1.9V between pin 1 & 2 of the Output Voltage Cable (one that enters the electronics box)

So this is what I have so far, starting at the plasma cutter.

measuring 2.6V on the pins in the connector on the front of the plasma cutter (red on right and black on left).

measuring -2.3V on the div output cable from the VIM (red inside barrel and black measuring outside the barrel).

Measured -1.9V between pin 1 & 2 of the Output Voltage Cable (one that enters the electronics box)

OK. It appears that the polarity is reversed in your aviation connector that connects to the plasma cutter. You can open the connector and switch the wires to correct the polarity.

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spoke with Langmuir and they suggested I do the following:
Notice the wire labeled C. I believe that wire comes from IHS. C may eventually connect to the white wire coming from THC connector but leave C alone. I recommend trying to switch A and B. A and B both come in through the THC connection port.

If the data you provided was accurate it would seem the cable connecting the divided voltage coming from the plasma cutter and going to the VIM is wired wrong. If switching the wires inside does not fix the issue then a new cable will also not fix the issue. The wire switch should prove polarity is the issue. You can switch the wires back if switching works and then we could send a cable.

So, I just did what they suggested and switched those wires and still the same issue. Any thoughts?

If you are getting a negative voltage. What do you get if you switch the leads on your meter?

Then just to make sure are you using ac or DC on your meter? I am guessing you are using DC just making sure.

You switched the two wires coming into the THC port, correct? The white wires are for the IHS and aren’t involved in the voltage reading.

If you’re still getting zero volts, then something is not hooked to the board correctly. Follow those two wires and make sure they are connected to the board.

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If the polarity is reversed, then the output voltage in fire control will read 0.0 vdc.

I had the same problem with mine. Wired per the instructions (checked and rechecked 5 friggin times) just to find out that the wires somewhere were wrong, so I just switched the two at the CP cord to the VIM cord. Now I have voltage in firecontrol.

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Correct. There is a grey and white wire coming out of the THC port so I then switched them making each wire have a grey line and white line.

thanks for coming to help. Could you walk that out a little clearer; sorry new to all this. Which is the CP cord and what did you switch?

If I am understanding right, Langmuir said that is not the issue if what I did in the picture above didnt fix the issue. Is that true?

I had to delete the original, and post edit since I just reread the entire thread in detail.

In short, you were working fine, parked the system for a month then came back and you are getting an ohms resistance reading that may or may not have been there before you parked it.

Did something in you setup short out?..possibly. Never underestimate the power of corrosion and dust to screw with electronics. I have had several electrical control systems that were giving every indication of being fried, that worked perfectly fine after a good cleaning to get all the dust off the control board, and clean the connections of corrosion.

Did your cables and plugs suddenly switch internally - NO! It was all working correctly before you replaced the control board which may or may not have been bad.

Are you absolutely sure that you put all the wires and plugs inside the control box back in the correct spots on the replacement board?

Did you take pictures of everything inside before you took it apart? If so, scrutinize those pictures and verify that your replacement is wired the same.

What else changed from last month (well 2 months now) when it was all working fine to now?

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Deleted by me

@Univ.Sculpt - Any luck? Keep the thread posted for either help or your solution so others may benefit.

No luck so far but an update and maybe the community can continue helping me get a resolution.

Per Langmuirs instructions, I again switched the THC wires (per the last image above) and measured the voltage at A1 to GND while cutting. Before making this switch with the wires, I was getting 0v between the two. After making the change in wires, I was getting 1.2v while cutting.

Next test I will do will be to cut with THC enabled and see if I am getting Live Volts greater than zero since making this switch in the wires.

Any thoughts?

As always, follow Langmuir instructions first. You are getting voltage now, so it should work.