BrokenBiker
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burn back is meant to control how much wire is left sticking out after you terminate the arc
- Thread starter Gareth J
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Post #2 of this thread has a typical schematic for the Migatronic control logic contained in the box which connects with a 9-pin D-sub plug:
The contactor and gas valve are AC components driven by a TRIAC, but the simple permanent-magnet DC motor is electronically controlled by power transistors, with no relays or mechanical brake involved.
I think that there is an electronic fault on the board, in the logic for on/off switching, possibly around the 2T/4T area, or in the higher-powered drive/braking transistors. This may be caused by a component ageing and/or being affected by heat. It will need power-on component-level troubleshooting to fix this, or you could do some static Ohms tests and speculatively replace likely components.
The basic trigger/wirefeed/speed control functions of the control box could be replaced by a relay and a generic eBay motor speed controller ( "PWM speed controller" ), but it would take some work to integrate this.
Perhaps if you put a couple of low-power ( one or two Watts ) 12v bulbs in series and wired them across the 24v motor wires, the flashing on/off would help to decide if the error is influenced by the Spot/Stitch/2T/4T modes?
The contactor and gas valve are AC components driven by a TRIAC, but the simple permanent-magnet DC motor is electronically controlled by power transistors, with no relays or mechanical brake involved.
I think that there is an electronic fault on the board, in the logic for on/off switching, possibly around the 2T/4T area, or in the higher-powered drive/braking transistors. This may be caused by a component ageing and/or being affected by heat. It will need power-on component-level troubleshooting to fix this, or you could do some static Ohms tests and speculatively replace likely components.
The basic trigger/wirefeed/speed control functions of the control box could be replaced by a relay and a generic eBay motor speed controller ( "PWM speed controller" ), but it would take some work to integrate this.
Perhaps if you put a couple of low-power ( one or two Watts ) 12v bulbs in series and wired them across the 24v motor wires, the flashing on/off would help to decide if the error is influenced by the Spot/Stitch/2T/4T modes?
Tec-Arc in York would probably be able to fix the control box if you disconnected it at the 9-pin plug and sent it to them, or maybe you could find a "Spares & Repairs" Migatronic and swap the box.
I do have Migatronic, but not sure which model. It is in a remote garage, I could check it....
I do have Migatronic, but not sure which model. It is in a remote garage, I could check it....
Gareth J
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I know. And I may be wrong about the setting I'm on about. But stick out length is what it depicts and altering it changes the duration of post flow of gas (potentially amongst other things I can't detect)
Gareth J
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Thank you,
Yes, that sounds similar to what I achieved with the welder I put a cheap pwm into. I don't recall the details but could open it up and copy if I did get the time. Or just plump for a whole suitcase wire feed unit and try to marry that up.
I can certainly try a bit more probing with test bulbs/a multimeter. But attempting to test stuff on a circuit board is going to end in confusion and take ages in the process I'm sure.
Yea, I have been keeping my ear to the ground for similar models for a while on eBay. But they don't come up much at all! Will contact Tec-Arc and see if they mind looking.
To be honest, now I've got a handle on how to run it without making the motor lag, I can fairly comfortably carry on using it. So long as I leave a bit of time between spot welds. For now at least.
See what Tec-Arc suggest. If you're desperate, I'm in Truro and could take a look at it, but it wouldn't be fast. I'm not an electrical engineer by any means, but have a variety of test equipment and electronics tools and a workmanlike ability to troubleshoot broken electronics as a hobby and to keep my hi-fi and tapes running. Sometimes on looking at a board there's an obvious problem that doesn't need a working knowledge of the whole circuit to repair, and the components are all of a size where their values can be read and the soldering's not microscopic.
I went down a rabbit hole looking for schematics too and wonder if post #9 of the following thread is more like yours as similar board and the schematic has the mode switch.
What mode was it in when you took the video, to me that video's audio suggests it was also holding the main contactor in until you paused, then it dropped out, then the final pull it worked as expected - Did I interpret that correctly?
Given the circuit diagram for mode selection, it would be worth cleaning and checking that switch (if you haven't already), along with any related post-weld delay control pots, even if you've changed them recently. After that you could resolder each point on the pcb in case it is a dry joint. But then, if it's not electo-mechnical you're into component level diagnostics as Eddie said above.
What mode was it in when you took the video, to me that video's audio suggests it was also holding the main contactor in until you paused, then it dropped out, then the final pull it worked as expected - Did I interpret that correctly?
Given the circuit diagram for mode selection, it would be worth cleaning and checking that switch (if you haven't already), along with any related post-weld delay control pots, even if you've changed them recently. After that you could resolder each point on the pcb in case it is a dry joint. But then, if it's not electo-mechnical you're into component level diagnostics as Eddie said above.
Gareth J
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Regarding the mode position switch, it's only possible to tell on either the standard weld setting, or the pulse weld setting. Both produce the same results. On either other setting (toggle on/off or timed spot) you can't cycle through to a restart fast enough to cause the drop out/lag.
I reckon that control box from that thread would just about fit straight into this machine.
In that video, it's confusing as the other main noise you hear is the gas solenoid, which, because the stick out knob was wound all the way, was staying open for often longer than it took to pull the trigger on/off/on. So didn't click off.
You can occasionally hear the main contactor thumping but its loud ess varies. Sometimes it thumps in with a fair whack, other times it's quieter.
Anyway, the torch is live correctly and gas solenoid fires reliably with the trigger. If they were all delayed together it would be less of a bother as I wouldn't keep sticking wire to the tip when the wirefeed fails to fire straight away.
Thank you for the offer.
I can't see anything blindingly obvious. It's not a complete write off yet as, now I've ascertained how to reliably avoid it, I can workaround the issue given the little welding I do. But that said, if things deteriorate and/or professional services are impractical, I may well be glad of a better pair of eyes.
mike 109444
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This is the motor that was in my Bora mig. 4 wire motor. 2 wires had power to one field till triger pressed then that went off and other pair of wires powered motor
Erie Fred
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"Burn Back" does not change the gas flow.
It changes the time the feed motor stops & the welding voltage is turned off.
The circuit diagram linked to by @rich_c in post #27 is the correct one.
The motor speed controller uses two large diodes and a Siemens DE11A13 "dual thyristor" as a half-controlled bridge rectifier across the 24v AC power supply. Motor speed is controlled by varying the firing angle of the two thyristors.
The control box plug has 14 pins, not 9.
The AC supply is fed in on Pins A and D and L and P.
The wirefeed motor Field winding connects to Pins B and M. As @mike 109444 suggested in Post #31, this is energised alone to act as a brake.
The brushes and armature of the motor connect at Pins C and R.
The contactor and gas valve, driven by the BT134 TRIAC, connect across Pins H and L and P.
The motor speed controller uses two large diodes and a Siemens DE11A13 "dual thyristor" as a half-controlled bridge rectifier across the 24v AC power supply. Motor speed is controlled by varying the firing angle of the two thyristors.
The control box plug has 14 pins, not 9.
The AC supply is fed in on Pins A and D and L and P.
The wirefeed motor Field winding connects to Pins B and M. As @mike 109444 suggested in Post #31, this is energised alone to act as a brake.
The brushes and armature of the motor connect at Pins C and R.
The contactor and gas valve, driven by the BT134 TRIAC, connect across Pins H and L and P.
