Thermal arc 175SE / ESAB buddy arc 180

[Jimbo Mc]

Hello all
Just wondering if anybody knows the rating of the Varistor element on the PCB.If someone has one and could pull the cover off and take a picture or put up the rating of it that would be super as I have to replace my one.
Thanks in advance
Regards James

 

[eddie49]

Hello and welcome to the Forum !

A Varistor is also be known as a VDR - a voltage dependent resistor, where the resistance decreases as the voltage increases. They are typically used to protect electronic devices by absorbing high-voltage spikes.
Perhaps the component you need is the soft-start thermistor ? They are usually from 20 to 100 Ohms.
This thread describes a similar failure in a 175SE inverter arc welder:

Thermal arc 175te PTC/NTC

Hi new here i recently got hold of the thermal arc 175te for cheap as not working kept blowing fuses upon inspection i noticed a blown capacitor and a bad ibgt so i ordered new and replaced them. The machine powered up for a second a went bang and blew the same cap upon further research...

www.mig-welding.co.uk

Note that as mentioned there, failure of this component is often caused by a short-circuit of the power semiconductors in the inverter switching stage.

 

[Jimbo Mc]

Hello and welcome to the Forum !

A Varistor is also be known as a VDR - a voltage dependent resistor, where the resistance decreases as the voltage increases. They are typically used to protect electronic devices by absorbing high-voltage spikes.
Perhaps the component you need is the soft-start thermistor ? They are usually from 20 to 100 Ohms.
This thread describes a similar failure in a 175SE inverter arc welder:

Thermal arc 175te PTC/NTC

Hi new here i recently got hold of the thermal arc 175te for cheap as not working kept blowing fuses upon inspection i noticed a blown capacitor and a bad ibgt so i ordered new and replaced them. The machine powered up for a second a went bang and blew the same cap upon further research...

www.mig-welding.co.uk

Note that as mentioned there, failure of this component is often caused by a short-circuit of the power semiconductors in the inverter switching stage.

Hi Eddie thanks for reply
It's this component here as circled in the picture.
Would that be the soft start thermistor.

 

[Jimbo Mc]

expand...

Hi Eddie thanks for reply
It's this component here as circled in the picture.
Would that be the soft start thermistor.

 

[Jimbo Mc]

Here's a closer picture.Any ideas what it is or why it would blow.

 

[eddie49]

Does the welder still work?
If it does, that component may be a varistor - rated at about 600v, to protect the input bridge rectifier, and wired in parallel with the AC mains input, after the noise-suppression mains filter. It may be just a simple capacitor.
If the welder does not work, then the failed component is probably the soft-start thermistor, in series and valued 20 to 100 Ohms.
Is there anything printed on the PCB in white silk-screen ink under the component?
A close-up photo of both sides of the board in that area would help to identify if the component is in parallel or in series with the mains supply.

 

[Jimbo Mc]

Yes it's definitely a Varistor.Welder is starting without it.I just need to be sure I'm putting in the correct rated varistor on the board but I can not get any information off my one.

 

[eddie49]

The varistor is a 431KD20. It is ceramic zinc-oxide, rated at 430 volts, +/- 10% tolerance, 20mm in diameter. Datasheet:

https://www.mouser.co.uk/ProductDetail/YAGEO/431KD20?qs=PzGy0jfpSMsSRAVCu43rsw%3D%3D

E.g available here:

Pardon our interruption...

 

[Jimbo Mc]

The varistor is a 431KD20. It is ceramic zinc-oxide, rated at 430 volts, +/- 10% tolerance, 20mm in diameter. Datasheet:

https://www.mouser.co.uk/ProductDetail/YAGEO/431KD20?qs=PzGy0jfpSMsSRAVCu43rsw%3D%3D

E.g available here:

Pardon our interruption...

Would that be the same 20D431K Varistor.Thanks Eddie

 

[eddie49]

Yes, that is the same part, just with the numbers and letters in a different order. E.G.:

3 Metal Oxide Varistor MOV 20D431K 275VAC UK Stock (120) | eBay

Epoxy coated disc construction with radial leads.UL & CSA approved. >330V nom. Lead pitch F. Rated Power (W). Max Energy 2ms (Joule). Peak Transient Current (A).

www.ebay.co.uk

 

[Jimbo Mc]

Super.Thanks for all your help Eddie.I will keep you posted on the outcome of the repair