TIG Welder Overheating

[masterkorp]

Hello everyone,

So yesterday my TIG Welder decided to stop working.

The welder only welds for 2-3 seconds and the it just stops welding. The overheating light just comes on. But I am pretty sure it ain't overheating.

So I opened the welder and I think I found the temperature sensor.

I've tried the following:
- Disconnecting the possible sensor makes the same result, which either means I am totally wrong or the sensor is totally dead and the circuit has a failsafe when no connectivity at is given
- Shorting the pins together makes the overheating light immediately come on. (Without start welding) which kinda enforces I am on the right track
- The pin has 24v when machine is connected
- I could not read any resistance values from the possible temperature sensor.

I think what I will try next is buying a 10k, 1k and 100 ohms resistance and connected them to the pin and check if I see any change in the behaviour.

Any ideas are welcome! I really need this machine to work.

[jlmoon]

Some documentation and more data would best to determine your problem. 
It is highly recommended not attempting any unknown resistor shunts or bridges unless you know what you're bypassing or shunting. 
Schematics or service documents are your top priority.

[tautech]

In an inverter style welder the are 2 possible locations for the sensor, in the transformer and on the switching device heatsink. Maybe both.
Which is yours?
Can you remove the sensor and post a photo?

[masterkorp]

Some documentation and more data would best to determine your problem. 
It is highly recommended not attempting any unknown resistor shunts or bridges unless you know what you're bypassing or shunting. 
Schematics or service documents are your top priority.

I could not find any schematics of this china welder. Please if someone could get me anything I would be thankful.

In an inverter style welder the are 2 possible locations for the sensor, in the transformer and on the switching device heatsink. Maybe both.
Which is yours?
Can you remove the sensor and post a photo?

Mine is an inverter style welder. I do think I am correct with the sensor location (last attached picture)

[jlmoon]

Can you post the Manufacturer & Model Number ?

[Seekonk]

Even though it says over temp light, these often serve multiple functions.  Unplugging the sensor and having the light come on immediately makes me believe the fault is not overtemp at all.

[masterkorp]

So I yesterday night I've made a tool to extract the temperature sensor.


And as it turns out its a fuse not a sensor
The fuse is BR-B2D at 95C apparently its the 24vdc version since the voltage coming of the pins is 24v
Current conclusions are:

• This is why disconnecting the sensor/fuse had the exact same effect has with it on.
• Also explains why the light comes one immediately after shorting the pins together, no matter what resistor I put in there
• The problem may be elsewhere, which means I am fucked
• I really need and try to find the schematics

Can you post the Manufacturer & Model Number ?

I wish I knew this, but it seems that the manufacturer and model is not mentioned anywhere on the machine. No documentation came with it.
The best I can do I to post a link to a very similar machine from the exactly the same seller I bought .I have a friend that has that exact model and its working fine so far. I've compared pictures from both machines and they look exactly the same.

Also i've tried that email, and I get no answers.

Any input would be very welcome at this point! As I am really out of budget for a new proper machine, and I really need this working,

[masterkorp]

Another link of the same welder I have

[Psi]

I think a lot of these welders are copy's or rebrands of jasic welders

The same temp led may get tripped from overcurrent which could happen if one of the power FETs/igbts is a bit faulty but not totally dead.

If it was me I would be checking all the power FETs/igbt's first because a fault there won't trip a fault condition forever. Repeated attempts to start it with a partial short will damage it more until Bang!  And then you'd need to replace all the FETs and maybe more.

Just my thoughts on it

[masterkorp]

I think a lot of these welders are copy's or rebrands of jasic welders

The same temp led may get tripped from overcurrent which could happen if one of the power FETs/igbts is a bit faulty but not totally dead.

Thanks for the info.

If it was me I would be checking all the power FETs/igbt's first because a fault there won't trip a fault condition forever. Repeated attempts to start it with a partial short will damage it more until Bang!  And then you'd need to replace all the FETs and maybe more.

Just my thoughts on it

Ok, how do I do that ?

[masterkorp]

I followed the circuit and it seems to be like this:

D6 (the red led) ->R30 -> R29 -> R28 -> (to the PCB that is vertical) -> R22 -> R21 -> C12 -> Q4 -> Q3 -> R15 and the goes to the most upper left pin of that mosfet/whatever.

It was that number BCPB-K01-D which a googling gives me nothing.

So I've tried to remove that sticker and check if there is anything under it.




And it seems to be this number VA28A 3525A which then again google gives me nothing.

Some new questions:
How the heck can I find information about these numbers ?
Can I debug this with just a multimeter ?

[mentaldemise]

Might it be one of these: https://www.fairchildsemi.com/datasheets/KA/KA3525A.pdf

[masterkorp]

Might it be one of these: https://www.fairchildsemi.com/datasheets/KA/KA3525A.pdf

Thanks, how can I test if it working correctly ?

[masterkorp]

Hello everyone.

So I completely disassembled the whole welder and inspected all the board and such, and found this:


And found what seems to be a "nose monkey" shorting those 2 pins together, also completely sprayed all the PCBs with electrical cleaner spray and the welder works again!

I had almost a week of downtime on this machine. I have a lot of work to repay for.

This being said. I plan to get a proper machine long term (I always wanted but no budget for it yet).

Thanks to everyone that helped one way or another !

[Tallie]

Glad you got it fixed! My guess would've been the spark gap(assuming it has one).

[masterkorp]

Glad you got it fixed! My guess would've been the spark gap(assuming it has one).

What is the "spark gap" ?

[Tallie]

Glad you got it fixed! My guess would've been the spark gap(assuming it has one).

What is the "spark gap" ?

Works the same way as on a Tesla coil... basically. It allows the circuit capacitance to charge and discharge.

[tautech]

Glad you got it fixed! My guess would've been the spark gap(assuming it has one).

What is the "spark gap" ?

Works the same way as on a Tesla coil... basically. It allows the circuit capacitance to charge and discharge.

Yep, it's part of the HF circuit for easier arc establishment at start of welding.
Older welders would whistle when HF was engaged.
Pretty much outlawed now because of the horrible EMI interference it creates.

I'd expect in this one if it has an HF mode it done electronically.

@masterkorp
 
You can put off that eye test for a bit now.
Good find, well done.

[masterkorp]

Yep, it's part of the HF circuit for easier arc establishment at start of welding.
Older welders would whistle when HF was engaged.
Pretty much outlawed now because of the horrible EMI interference it creates.

I'd expect in this one if it has an HF mode it done electronically.

My welder seems to be like this, it make a horrible noise before starting.
I got the hang of it, by tapping the rod onto the metal to start the welding process.
This happens more in AC than in DC.

@masterkorp
 
You can put off that eye test for a bit now.
Good find, well done.

Thanks !

[G7PSK]

All the modern TIG units that I have had use an HF block that cannot be serviced as not only are the electronics encapsulated the whole thing is moulded into a plastic case, on the other hand the best TIG unit I ever had was an ESAB unit made in the late 50's or early 60's and the HF unit consisted of a Bosch spark plug and ignition coil and some very high voltage silver mica capacitors, it was built like a tank weighed 280 KG including the transformer which was in over 100 litres of oil and would run 400 amps all day no modern unit would touch it. And the idiot that I am traded it for a modern light weight unit just for one job where I neede to get it up some stairs.

[Kuria]

I Know this an old post but I have a similar problem. My welder OC light is always on and while the machine switches on and the knobs and display seem to function
It's doing nothing it's blocked. I wrote a lengthy post on it ..... Any advice?