Please help me fix the issue with this automation board on Cutmaster 51

[gianniravioli]

Hello,

I was in a process of changing electronics on very old plasma CNC machine and made a mistake by providing the voltage 24-36V to the CPC connector, if I understand correctly pins 3 and 4 should be shorted but by mistake i wired relay wrongly and pushed the voltage to those pins..

I have tried to manually short pins 3 and 4 on CPC without luck, machine does not release air and does not create an arc. Torch is firmly connected, all consumables are fine and air pressure is sufficient.

Would I be able to fix this by replacing dead components? How to figure out which components are dead in first place?

Any help is appreciated.

Thank you!

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[tcaudle]

Looking at the top of the board photo there is not any visibly blown parts (which is consistent with logic circuits unless their VCC supply voyage gets hit by large over volatge). The Torch fire is going to be an input that basically shorts across the torch switch pair to fire the torch. With the plasma off ,see if you can trace the torch cable inside the unit and find the two smaller wires from the torch that would fire the torch from a hand torah. There will be more than one pair of smaller gauge wires
Get the block schematic of your unit (usually in the User Manual or the Service Manual) and the wire colors will be listed. If you have a hand torch its easier as you can trip the switch and trace the two wires that show a short . If you can short across the torch switch pair inside and fire the torch . you can bypass that 3-4 pin and still use the ARC OK (OK to MOVE) and the Divided volts (pins 5 - 6) . Just use your relay contacts on the THC to trip the torch switch pair
If the torch will not fire by using the torch switch pair inside that is a bad thing because that whole circuit is blown.

[tcaudle]

Update. Get the Thermal Dynamics CutMaster51 Service Manaul PDF (omline: Copyrighted material so can't post here ) and on the addendum pages 81-84 there are Block diagrams with connectors and wire colors for the torch and the Automation Interface card. Note the hand torch fire pair are the Green White pair, but that pair does not appear to be connected on a Machine torch. The Torcn fire pair leaves the Automation Interface but it appears to be a logic signal rather than a switch closure so I doubt shorting that pair would work and might cause damage further back!

Armed with that schematic and the connector pin out you might could get a good tech to at least cheek the input components for bad parts)

[gianniravioli]

Thank you for your reply @tcaudle.

I have been reading manuals and removed the automation board for testing. There is no damage it seems here.. What worries me is that pin 3 and pin 4 are directly connected to logic input on Main PC Board (TS1 & TS2 connector).. If this big voltage went there i am afraid those are fried.. I don't see any resistor in between.

This machine does not use THC and haven't planned to use one for now so I am not concerned about anything apart from start/stop. It has mechanized torch. Plasma machine turn the air valve on torch and start the arc. I am able to turn air valve on torch externally but haven't found a way to start the arc externally.. Not sure if it is possible actually.

If anyone has any idea, I would appreciate that a lot!

Thank you

[tcaudle]

How were you going to do that before? Software has to trigger some form of output . That same 24V output you used before can be used to trigger a simple relay and those contacts can be used to fire the torch externally. A 24V small relay can take SOME over voltage and you can put a zener across the coil of say 28 volts to kill spikes.
If you don't have IHS (touch off ) to set pierce height and cut height and you have no THC then a manual torch switch (Manual appendix shows Remote Torch Fire ) might be all you need.

[gianniravioli]

Before it stopped working software was triggering a relay which shorted pins 3 and 4 on CPC cable. From what i understand those pins 3 and 4 are responsible for telling the machine internally to release the air and start the torch - this should be equivalent to manual torch trigger. This was being done by this automation board. But that does not work anymore.

Screenshot 2025-04-27 093821.png

- On this image you can see that torch switch in this case dry contact over relay is being sent via CPC connector to the automation board (marked as 1. on image) and that signal is being transfered via J1 connector (pins 5 & 6) to the main board (marked as 2. on image).

Screenshot 2025-04-27 094415.png

- On this image you can see where this signal reach the main board (3.). Basically this E23,E24,E25,E26 are connected to the automation board..
- Also on same image I have noticed on the left side of the board that there is torch switch which perhaps i could use but I am not sure how to wire it correctly.. That pin 21 should be connected with something but not sure if that is pin 20 (RTN) or 22 (+12VDC).

This automation board is optional and was only used for turning torch on & off. My question is now when I removed the automation board is how to find correct pins to start the torch.

[gianniravioli]

I dig deeper into manual and have found that there are pins 3 and 4 that connects directly to the ATC torch connector. I believe that this are the ones I should short to simulate manual torch..

Screenshot 2025-04-27 112933.png

[adbuch]

I have been following this. Let us know if you have found a resolution to your problem.
Thanks,
David

[gianniravioli]

Hello @adbuch,

Thank you for following my struggle..

I have found some time today to test bit more but without any luck...

What I did is I tapped directly to the ATC wires inside the machine itself (on main board). Traced the 3 and 4 pin from the torch and shorted them manually with switch but nothing happened.. Air is not comming out (solenoid is not being being triggered) - Solenoid is not jammed as I have tested it manually by applying 24V external power.

I have also visually inspected main board & logic board and cant find anything suspicious at least to naked eye.

Unfortunately I am running out of knowledge and ideas..

If anyone has any additional recommendation; I am willing to test it out.

Thank you!