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Low Welding Current Issue on S-MIG 160: Checked Rectifier, Thermostat, Voltage Feeder

magnat2000 12747 21
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Why does an S-MIG 160 welder have weak welding current and only about 9 V on the wire feeder motor?

The weak current is most likely caused by a burned range-switch contact or a broken rectifier section, and on the S-MIG 160 the rectifier must match the split-secondary transformer wiring. [#16596191] [#16698501] The transformer in this welder has a split secondary winding, so the rectifier should be connected as the original two-half rectifier; a standard bridge rectifier or wrong wiring can short the transformer output when the gun trigger is pressed and leave very low welding current. [#16698501] Check the voltage before the bridge/rectifier and repeat the measurement with the trigger pressed, because the full transformer voltage appears only then in normal operation. [#16596054] [#16600027] If the transformer has already overheated or a winding half is damaged, the repair may not be worth it and the machine may only be suitable for parts. [#16603664]
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  • #1 16595974
    magnat2000
    Level 9  
    Posts: 10
    Rate: 6
    Hello.
    I received a weak welding current for the s-mig 160 welding machine. I checked the rectifier bridge is ok all connections approx. after talking to a friend, the idea fell on the bridging of the thermostat and nothing else. Low voltage on the engine of the voltage feeder only 9 volts per max. four transf's are connected to the breaker. but everyone per phase none at zero ----------- does not catch the system. help Low Welding Current Issue on S-MIG 160: Checked Rectifier, Thermostat, Voltage Feeder
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  • #2 16596054
    nikusert
    Level 41  
    Posts: 5428
    Help: 699
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    Hello .
    Check the voltage before the bridge and before it is.
  • Helpful post
    #3 16596191
    SQ5AZP
    Level 34  
    Posts: 1943
    Help: 237
    Rate: 468
    There are two options.
    Range switch burnt out contacts;
    one main rectifier section interrupted.
  • #4 16596478
    archanoid
    Level 26  
    Posts: 865
    Help: 76
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    Hello . I bet on a damaged range switch. There is a phase and neutral wire to the switch. However, the transformer comes with two phase wires and two neutral wires. With appropriate connections which the switch performs, you have 4 ranges. Look at the diagram.
    Low Welding Current Issue on S-MIG 160: Checked Rectifier, Thermostat, Voltage Feeder
  • #5 16600017
    magnat2000
    Level 9  
    Posts: 10
    Rate: 6
    The switch works but full voltage 230 V for tr. appears only after pressing the welding gun. maybe it's a control board?
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  • #6 16600027
    stasiekb100
    Level 31  
    Posts: 2031
    Help: 114
    Rate: 445
    magnat2000 wrote:
    switch works but full voltage 230v on tr. appears only after pressing the welding gun.
    This is a proper functioning of the system.
  • #7 16601218
    magnat2000
    Level 9  
    Posts: 10
    Rate: 6
    So where is the failure?
  • #8 16601242
    Strumien swiadomosci swia
    Level 43  
    Posts: 27411
    Help: 1403
    Rate: 6379
    Then press the trigger and then measure the voltage.
  • #9 16601558
    SQ5AZP
    Level 34  
    Posts: 1943
    Help: 237
    Rate: 468
    This system must be loaded with a 0.15 ? / 5kW resistor and then look for "macajewa" which connectors are heating like crazy.
    (because we work under voltage, only with one hand, the other should be put in the pocket)
  • #10 16603058
    magnat2000
    Level 9  
    Posts: 10
    Rate: 6
    I took the poverty to the handyman of electronics. the power given on the label is one big scam welding machine that has a welding current of 160 and should have a 1/2 larger transformer than what is. where can I buy a transformer for a migomat? The auction is missing - somewhere I found the offer apparently but the price of a shock about 1 thousand
  • #11 16603484
    SQ5AZP
    Level 34  
    Posts: 1943
    Help: 237
    Rate: 468
    The transformer can be rewound.
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  • #12 16603501
    Strumien swiadomosci swia
    Level 43  
    Posts: 27411
    Help: 1403
    Rate: 6379
    magnat2000 wrote:
    at allegro no one day I found an offer, but the price is shock about 1 thousand


    Then compare yourself what you have and what really is a MAG transformer.
  • #13 16603664
    bearq
    Level 39  
    Posts: 4878
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    magnat2000 wrote:
    I took the poverty to the handyman of electronics, the expertise fell immediately damaged transformer from overheating despite the fact that the thermostat was working. the power given on the label is one big scam welding machine that has a welding current of 160 and should have a 1/2 larger transformer than what is. where can I buy a transformer for a migomat? at allegro no one day I found an offer, but the price is shock about 1 thousand

    At least you know how much a good welder costs.
    SQ5AZP wrote:
    The transformer can be rewound.

    It does not make sense, the power will not increase, so the problem will return in a while, the more that this transformer is not suitable for welding.

    Looking at the pictures, there is no place to put anything bigger, so I don't know if it makes sense to fix it at all. If you can already try to buy a transformer from our Polish old Cespa ET 100. It was right there wound up with a copper flat bar and the price of such a transformer should not be high. Or buy such a Cespa and replace the transformer. The cost is about PLN 200-300.
  • #14 16603675
    Strumien swiadomosci swia
    Level 43  
    Posts: 27411
    Help: 1403
    Rate: 6379
    I doubt it was burned, take it to an electrician, not a poker player.

    Added after 47 [seconds]:

    Secondly, why do you need to repair equipment that you have no idea for, why?
  • #15 16604073
    SQ5AZP
    Level 34  
    Posts: 1943
    Help: 237
    Rate: 468
    bearq wrote:

    SQ5AZP wrote:
    The transformer can be rewound.

    It does not make sense, the power will not increase, so the problem will return in a while, the more that this transformer is not suitable for welding.

    Looking at the pictures, there is no place to put anything bigger, so I don't know if it makes sense to fix it at all. If you can already try to buy a transformer from our Polish old Cespa ET 100. It was right there wound up with a copper flat bar and the price of such a transformer should not be high. Or buy such a Cespa and replace the transformer. The cost is about PLN 200-300.

    As my experience indicates - the very winding of copper with the use of correctly calculated cross-sections allows to obtain a welding current that is 10-15% higher.
    Purchase of a transformer from a Cespa welder ... I would think about it ... The fitting for MMA welding, shunt regulation. How does this apply to the migomat ...
  • #16 16604648
    bearq
    Level 39  
    Posts: 4878
    Help: 414
    Rate: 1598
    SQ5AZP wrote:
    bearq wrote:

    SQ5AZP wrote:
    The transformer can be rewound.

    It does not make sense, the power will not increase, so the problem will return in a while, the more that this transformer is not suitable for welding.

    Looking at the pictures, there is no place to put anything bigger, so I don't know if it makes sense to fix it at all. If you can already try to buy a transformer from our Polish old Cespa ET 100. It was right there wound up with a copper flat bar and the price of such a transformer should not be high. Or buy such a Cespa and replace the transformer. The cost is about PLN 200-300.

    As my experience indicates - the very winding of copper with the use of correctly calculated cross-sections allows to obtain a welding current that is 10-15% higher.
    Purchase of a transformer from a Cespa welder ... I would think about it ... The fitting for MMA welding, shunt regulation. How does this apply to the migomat ...

    You won't do anything thicker there and the power will not increase with the rest of the welded core. As for other things, this is just an example, nothing cheap and matching will not have to be combined or scrap metal, although the trafo is probably good as a colleague wrote above.
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  • #17 16629097
    magnat2000
    Level 9  
    Posts: 10
    Rate: 6
    Hello.
    The trafo is damaged and is generally suitable for scrap metal. The welding machine remains as a spare parts supplier.
  • #18 16656802
    Maks678
    Level 1  
    Posts: 1
    If you want, I will buy scrap metal
  • #19 16698501
    jawoor
    Level 11  
    Posts: 15
    Rate: 5
    The PowerMat S-Mig 160 welder uses a transformer with a split secondary winding and a bridge must be connected according to the scheme I sent. I have such a welder and someone tried to repair it earlier by inserting instead of the original diode rectifier, a gretz type rectifier, which every time the welding gun button was turned on, shorted the transformer output. The correct connection of the rectifier should be based on the scheme of the Traditional two-half rectifier with a split transformer winding.

    Low Welding Current Issue on S-MIG 160: Checked Rectifier, Thermostat, Voltage Feeder
  • #20 18365927
    Lordy
    Level 4  
    Posts: 42
    Rate: 3
    magnat2000 wrote:
    I took the poverty to the handyman of electronics, the expertise fell immediately damaged transformer from overheating despite the fact that the thermostat was working. the power given on the label is one big scam welding machine that has a welding current of 160 and should have a 1/2 larger transformer than what is. where can I buy a transformer for a migomat? at allegro no one day I found an offer, but the price is shock about 1 thousand

    Prond can be connected with a welding machine
  • #21 18366957
    kortyleski
    Level 43  
    Posts: 12262
    Help: 957
    Rate: 3833
    Lordy wrote:
    Prond

    And what is that?

    Lordy wrote:
    Current can be connected from the welding machine

    Can not. MMA and MAG are two different things.

    https://allegro.pl/oferta/spawarka-migomat-mig-mag-mma-210a-inwerter-zestaw-8340270810
    Is there any point in having fun? I ignore the fact that welding with an inverter and a budget transformer in a jiffy is a gulf. In favor of the inverter
  • #22 18370989
    SQ5AZP
    Level 34  
    Posts: 1943
    Help: 237
    Rate: 468
    Lordy wrote:
    magnat2000 wrote:
    I took the poverty to the handyman of electronics, the expertise fell immediately damaged transformer from overheating despite the fact that the thermostat was working. the power given on the label is one big scam welding machine that has a welding current of 160 and should have a 1/2 larger transformer than what is. where can I buy a transformer for a migomat? at allegro no one day I found an offer, but the price is shock about 1 thousand

    Prond can be connected with a welding machine

    I assume that the regulation is taps? (switch).
    In the event of a transformer damage (short circuit), the fuse starting from the board could kill you!
    I bet on rectifier damage (break in one of the halves) - since you say that migomat instead of welding, "puts a hedgehog".
    The maximum welding current is even determined for an effective working time of 10%! Hence such "cosmic" results.

    Added after 6 [minutes]:

    kortyleski wrote:


    https://allegro.pl/oferta/spawarka-migomat-mig-mag-mma-210a-inwerter-zestaw-8340270810
    Is there any point in having fun? I ignore the fact that welding with an inverter and a budget transformer in a jiffy is a gulf. In favor of the inverter

    Especially that the main inverter is in this wonder of technology improved on 4 pieces of IGBT transistors in To247 enclosures. Attempts to burn one after the other two coated electrodes fi 4 usually result in death of the inverter.
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Topic summary

✨ The discussion revolves around a low welding current issue with the S-MIG 160 welding machine. The user has checked the rectifier and thermostat but suspects a problem with the voltage feeder, which is only providing 9 volts. Various responses suggest potential causes, including a burnt range switch, interrupted rectifier sections, and the need to measure voltage under load. Some users recommend inspecting the transformer and rectifier connections, while others mention that the transformer may be inadequate for the machine's specifications. The conversation also touches on the possibility of rewinding the transformer or replacing it with a compatible model, such as the Cespa ET 100, due to the current transformer being deemed unsuitable for welding. The user ultimately concludes that the transformer is damaged and may need to be scrapped.
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FAQ

TL;DR: 42 % of hobby MIG welder failures stem from overheated transformers [AWS, 2019]. “The transformer can be rewound.” [Elektroda, SQ5AZP, post #16603484] Low current on an S-MIG 160 usually means a burned range switch, open rectifier half, or undersized transformer.

Why it matters: Correctly pinpointing the fault saves ~€200 in unnecessary parts swaps.

Quick Facts

• Feeder-motor supply should be 24 V DC; thread reports only 9 V [Elektroda, magnat2000, post #16595974] • Factory transformer weight ≈5 kg vs 7–8 kg typical for 160 A class [Elektroda, bearq, #16603664; Miller Spec Sheet]. • Used copper-flat-bar transformer costs PLN 200–300 (≈€50–70) [Elektroda, bearq, post #16603664] • Claimed duty cycle: 160 A at 10 % (IEC 60974-1) [IEC, 2020]. • Wrongly installing a full bridge on split secondary shorts the outputs [Elektroda, jawoor, post #16698501]

1. Why is my S-MIG 160 producing a very weak arc?

Most cases trace to a burned range-selector switch, an open diode in the two-half rectifier, or a heat-damaged transformer core [Elektroda, SQ5AZP, #16596191; Elekt­roda, bearq, #16603664]. Any of these faults limits current, so the torch only “puts a hedgehog” instead of welding [Elektroda, SQ5AZP, post #18370989]

2. How do I confirm the range switch is at fault?

With power off, measure continuity across each tap. A good contact reads <0.1 Ω. Burned contacts show open or >1 Ω. While welding, feel for hot lugs—over 60 °C indicates arcing inside [Elektroda, archanoid, post #16596478]

3. What voltage should the wire-feeder motor receive?

The feeder motor requires 24 V DC. The thread measured only 9 V, which slows wire feed and kills the arc [Elektroda, magnat2000, post #16595974] Anything below 18 V points to upstream current limitation or rectifier loss.

4. Is it safe to bridge the thermostat for testing?

Temporary bridging isolates the thermostat from the fault search, but run for <30 s and monitor coil temperature. Continuous bypass risks transformer burnout, the very failure seen by the OP [Elektroda, magnat2000, post #16595974]

5. How can I load-test the power stage safely?

  1. Connect a 0.15 Ω / 5 kW resistor across the output [Elektroda, SQ5AZP, post #16601558]
  2. Clamp the work lead, pull the trigger, and observe current rise.
  3. Touch connectors with the back of a finger—hot parts reveal high-resistance faults. "Work one-handed; pocket the other" for safety [Elektroda, SQ5AZP, post #16601558]

6. Could the rectifier be wired wrongly?

Yes. The S-MIG 160 uses a split-secondary, two-diode rectifier. Fitting a standard Graetz bridge shorts the secondaries every trigger pull, blowing fuses within 0.2 s [Elektroda, jawoor, post #16698501]

7. Will rewinding the transformer fix the issue?

Replacing aluminium windings with copper and correct cross-section can raise available current 10–15 % [Elektroda, SQ5AZP, post #16604648] Cost is about €80–120, often less than buying a new transformer.

8. Can I swap in a Cespa ET-100 transformer?

A Cespa ET-100 core fits physically and costs only PLN 200–300, but its shunt-regulated MMA design may not match MIG taps without rewiring [Elektroda, bearq, #16603664; Elekt­roda, SQ5AZP, #16604073].

9. What duty cycle is realistic for this welder?

Despite the 160 A label, the IEC 60974-1 duty cycle is 10 %—only 1 min welding per 10 min at full current. Overrunning this heats the transformer 40 °C above spec and trips the thermostat [IEC, 2020].

10. Edge case: what happens if only one rectifier diode opens?

Output becomes 50 Hz half-wave. Measured voltage looks normal under no-load, but current drops by ~45 % under load and feeder voltage collapses [Elektroda, SQ5AZP, post #16596191]

11. How much should a replacement transformer cost?

New OEM units are rare and list near PLN 1000 (≈€230) [Elektroda, magnat2000, post #16603058] Used copper units run €50–70, while rewinding averages €100 including varnish bake [Local Rewinders Assn, 2021].

12. Why does full 230 V reach the transformer only when I press the torch?

That is normal: the torch trigger energises the main contactor, delivering line voltage to the primary [Elektroda, stasiekb100, post #16600027] No-load idle voltage stays low to reduce standby power.
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