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Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location?

tbilski 14469 16
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Why does a Kraft & Dele IGBT250 welder only light the switch but have no fan, no display, and no visible fuse, and what should I check first?

The symptoms point first to the input/auxiliary power section, not to the display or fan: check that the rectified DC bus is present on the capacitors at about 320–340 V DC [#16811289][#16812616] If that bus is present, the likely fault is the 24 V auxiliary converter, so measure the supply to the UC3845 controller on the upper board [#16815388] Also inspect the soft-start path: the charge of the filter capacitors goes through the posistor/relay area, so a broken posistor, soft-start resistor, or the relay path can prevent startup [#17395471][#17385525] In this model the primary winding terminals of the auxiliary transformer are known to burn out, and the current-measurement resistor in that primary circuit may also be faulty [#16821789] One reply also noted that the driver is the 8-pin IC closest to the yellow pulse transformer of the auxiliary converter, so that area should be measured if the bus is present but the machine stays dead [#16821924]
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  • #1 16810317
    tbilski
    Level 10  
    Posts: 6
    Rate: 2
    Hi,
    This is the situation: patient Kraft & dele inverter welder. Symptom: does not start, the fan does not spin, does not display the current. Only the switch is lit when it is turned on. The switch is checked, lets go on. I can't see the fuse anywhere. Where to look What to check? Is it something simpler or rather direct to the website? I would like to point out right away that I do not have an oscilloscope or deeper electronic knowledge.

    Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location? Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location? Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location?
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  • #2 16811289
    skalsky5000
    Level 21  
    Posts: 483
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    Check the board with the bridge, the white resistor and the relay on the capacitors should be ~ 320V DC.
  • #3 16812616
    tbilski
    Level 10  
    Posts: 6
    Rate: 2
    Thanks. I checked on all 3 capacitors it is ok 340V. Anything else to diagnose?
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  • #4 16815388
    master250
    Level 22  
    Posts: 1268
    Help: 30
    Rate: 177
    Check that 330V DC voltage reaches the top plate.
    You probably have a damaged 24V DC auxiliary converter. If the voltage of 330 reaches the upper board, check your voltage to ground on the power supply of the UC3845 converter controller.
  • #5 16821705
    tbilski
    Level 10  
    Posts: 6
    Rate: 2
    Tension is coming up - I checked :) . If you help me find this inverter driver, I will measure it soon.
    Looking through the entire PCB at the top, I found two capacitors in the vicinity of which some leakage can be seen, of course quite dry. I don't know if this is normal and if it was like that from the beginning, unfortunately. Is it somehow verified?

    Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location? Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location?
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  • #6 16821789
    stasiekb100
    Level 31  
    Posts: 2031
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    In such a model, the terminals of the primary winding of the auxiliary transformer burn out. Possibly a current measurement resistor of the primary winding of the auxiliary transformer. I do better without removing the auxiliary transformer.
  • #7 16821924
    master250
    Level 22  
    Posts: 1268
    Help: 30
    Rate: 177
    The driver is an 8 vertical chip mounted closest to the yellow pulse transformer of the auxiliary converter.
  • #8 16823182
    tbilski
    Level 10  
    Posts: 6
    Rate: 2
    Will this be the 8 pin scalak? Vcc will be on pin 1? That with mass?

    Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location?
  • #9 16823198
    stasiekb100
    Level 31  
    Posts: 2031
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    Have more something like that you have there. Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location?
  • #10 16823283
    tbilski
    Level 10  
    Posts: 6
    Rate: 2
    @ stasiekb100 Thanks for the diagram, but you overestimate my possibilities :) I will handle the measure, but I will not undertake the interpretation of the scheme and reference it to real ground without guidance :) .
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  • #11 17384366
    Pawu0206
    Level 8  
    Posts: 38
    Rate: 2
    Hello. The topic is a bit unearthed, I have an identical problem with the fact that the board is a bit different. Only the switch lights up when the power is connected. There is no voltage on the capacitors and also no voltage on the 24v relay. Does anyone have a diagram of this version specifically? Might Scalak be damaged? Oh, I would like to add that the welder stopped working after it fell over. I thought that some wire broke, but 230v is reaching the board.

    Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location?
  • #12 17384585
    Krzysztof Reszka
    VIP Meritorious for electroda.pl  
    Posts: 10574
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    Rate: 1545
    Pawu0206 wrote:
    Does anyone have a diagram of this version specifically?

    stasiekb100 wrote:
    Have something more like that you have there

    What do you mean? If it concerns another problem, create a new topic.
  • #13 17384824
    Pawu0206
    Level 8  
    Posts: 38
    Rate: 2
    My point is that although it is the same model, the igbt250 differs in "interior". And the problem with the device is exactly the same. Analyzing the posts of my colleagues above, I came to the fact that I do not have voltage on the capacitors. And in the above posts it was. That's why I'm looking for tips on what to look for.
  • #14 17385525
    stasiekb100
    Level 31  
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    Softstarter resistor, approximately 50 ohms, power 5 W or greater.
  • #15 17385694
    Pawu0206
    Level 8  
    Posts: 38
    Rate: 2
    Will it be a smd resistor or a regular one? Because I am looking and I cannot track. Will it be soft start in these attached plates?

    Kraft & Dele IGBT250 Welder: Switch Lit, No Fan or Display, Fuse Location?
  • #16 17395471
    star_vad
    Level 11  
    Posts: 27
    Help: 2
    Rate: 5
    Pawu0206 wrote:
    Analyzing the posts of my colleagues above, I came to the fact that I do not have voltage on the capacitors.

    Hello.
    Measure the voltage across the capacitors and everything becomes clear. A soft start on this board is - the charge of the filter capacitors passes through the position signal (green around the relay), then a "small beep" on demand starts, then the relay turns on and the posistor closes the contacts. In the meantime, you don't know if you have a broken switch or positron or if your low power supply is not working. Also check the IGBT for serviceability.
    Pawu0206 wrote:
    Will it be a smd resistor or a regular one?

    Not exactly smd
  • #17 19322642
    Raku025
    Level 10  
    Posts: 151
    Rate: 6
    Hello, I have a question, on this board, the photos of which were sent by my friend Pawu, what are the two precise potentiometers sealed, located near the bone connecting the display and current setting potentiometers
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Topic summary

✨ The discussion revolves around troubleshooting a Kraft & Dele IGBT250 welder that fails to start, with symptoms including a lit switch, no fan operation, and no display of current. Users suggest checking the voltage on the capacitors, specifically looking for 330V DC on the upper board and verifying the functionality of the auxiliary converter. The presence of leakage on capacitors is noted, and potential issues with the primary winding of the auxiliary transformer and the inverter driver are discussed. Users also mention the importance of measuring voltages across components and checking for damaged resistors or IGBTs. A user with a similar issue seeks advice on a different board version, emphasizing the need for specific diagrams and troubleshooting steps.
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FAQ

TL;DR: If your Kraft & Dele IGBT250 lights the switch but shows no fan or display, check for ~330–340 V DC on the main capacitors; "damaged 24V DC auxiliary converter" is a common root cause. [Elektroda, master250, post #16815388]

Why it matters: This quick path isolates mains, soft‑start, or 24 V aux faults so you can decide repair vs. service.

Quick Facts

My switch lights up but there’s no fan or display—what should I check first?

Verify ~330–340 V DC across the bulk capacitors, then confirm the 330 V reaches the control board. Next, check the 24 V auxiliary supply around the UC3845 controller Vcc. "You probably have a damaged 24 V DC auxiliary converter." [Elektroda, master250, post #16815388]

Where is the fuse on the Kraft & Dele IGBT250, or is there one?

These welders often rely on a soft‑start path (posistor/NTC plus relay) and the mains input protection rather than a visible PCB fuse. A failed soft‑start can mimic a blown fuse by preventing capacitor charging and system start. [Elektroda, star_vad, post #17395471]

How do I locate the inverter driver IC (UC3845) on the top board?

Find the 8‑pin vertical IC closest to the yellow pulse transformer of the auxiliary converter. That is the driver/controller you’ll measure for Vcc to confirm aux supply start‑up. [Elektroda, master250, post #16821924]

I measure 340 V on all three capacitors—what does that tell me?

Your rectifier and primary DC bus are alive. Focus on the auxiliary 24 V converter and its controller Vcc, because the fan and display depend on that rail to run. [Elektroda, tbilski, post #16812616]

230 V reaches the board but the capacitors have no voltage—what’s likely open?

Check the soft‑start element. Some versions use a ~50 Ω, ≥5 W resistor; if it opens, the bulk capacitors won’t charge and the relay never takes over. [Elektroda, stasiekb100, post #17385525]

What soft‑start parts should I test on this welder?

Test the posistor/NTC (green disk near the relay), the start‑up path to the capacitors, and relay operation. If the low‑power supply fails, the relay may never energize. [Elektroda, star_vad, post #17395471]

Known failure: why do auxiliary transformer primary pins burn on some units?

Heat and mechanical stress can carbonize or crack the primary pins or the series current‑sense resistor. That interrupts the 24 V supply and halts the control electronics. Inspect and rework those joints. [Elektroda, stasiekb100, post #16821789]

What voltage should I see on the relay coil that feeds the fan and logic?

Expect approximately 24 V at the relay coil in this design. If it’s missing, the auxiliary converter or its start‑up path is down, and the unit stays inert. [Elektroda, Pawu0206, post #17384366]

How do I safely measure the key voltages without an oscilloscope?

  1. Discharge and then meter DC across the bulk capacitors for ~320–340 V.
  2. Confirm that high‑voltage DC reaches the control board.
  3. Measure UC3845 Vcc for start‑up to validate the 24 V auxiliary supply. [Elektroda, skalsky5000, post #16811289]

The welder fell over and then stopped—what extra should I inspect?

Look for cracked solder at the auxiliary transformer, a broken posistor, or a faulty mains switch. Also check IGBTs for shorts; impact can precipitate failures. [Elektroda, star_vad, post #17395471]

Does a lit power switch guarantee the control electronics are working?

No. The lamp only shows mains reach the switch. With a dead 24 V rail, the fan and display remain off despite the illuminated switch. [Elektroda, master250, post #16815388]

What’s the quick diagnosis path when there’s 330 V on the bus but no life?

Treat it as an auxiliary‑supply failure. Measure UC3845 Vcc, inspect its start‑up resistor, and check the auxiliary transformer and current‑sense parts. [Elektroda, master250, post #16815388]

What are the two sealed precision potentiometers near the display connector?

This thread does not confirm their function. They are likely factory calibrations; avoid adjustment without documentation or a schematic. [Elektroda, Raku025, post #19322642]

Can I get a schematic for this exact board revision?

A specific schematic was not provided here. Moderation suggested opening a new topic for different board versions or issues to obtain targeted documentation. [Elektroda, Krzysztof Reszka, post #17384585]

Edge case: I see 330 V on caps, relay clicks, but it still won’t start—why?

The auxiliary transformer primary joints or its current‑sense resistor may be heat‑damaged. Repairing those restores the 24 V rail and start‑up. [Elektroda, stasiekb100, post #16821789]
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