Tweco 301/lorch T300 ac/dc fault diagnosis

[Munkul]

Machine bought with e25 error code with nothing plugged in.
Started stripping it down, nothing obviously wrong.

Checked T-MAPRO board for reference voltages.
Nothing wrong, so board removed to reveal primary driver board T-PR300 and secondary rectifier board T-GWH300.

Primary IGBT modules on T-PR300 checked with multimeter according to service manual diagrams and the help of ChatGPT.
That left the mosfet, and secondary igbts and diodes on T-GWH300.


Removed cables and checked all diodes and igbts.
Hooray! Found an issue with one of the diode modules, so started to strip out the board.


Board removed to show the modules


Bad module

UFB210FA40P
Now, this is a discontinued product from Vishay, does anyone know where best to get one from in UK? Or the replacement part number which is UFB211FA40.

I'm not super hot with electronics, i only know enough to get by, so is there any likelihood that this part has damaged anything else? Like i said, I've checked all of the other diodes and igbts, all check ok.

Any assistance greatly appreciated

 

[tom2207]

well done on getting that far ,,, fingers crossed for ya

 

[m_c]

Digikey has a UK presence https://www.digikey.co.uk/en/produc...nductor-diodes-division/vs-ufb211fa40/5423283

 

[Jan-DIY]

Avoid mixing different types of diodes in this section.

This can cause an early breakdown.

Broken diodes are very common here.
In the very most cases it is only the diode.

 

[Munkul]

Aloid mixing different types of diodes in this section.

This can cause an early breakdown.

Broken diodes are very common here.
In the very most cases it is only the diode.

I've spoke to Lorch dealer, he has the correct Lorch part number on the shelf, but its an ST branded equivalent component, not Vishay.
Do you think this will be a problem?
I thought it was just the IGBTs that needed to be super balanced?

 

[Jan-DIY]

These are superfast diodes to rectify ac voltage from primary inverter.

If Lorch not recommend to change them all you can get lucky.
St stth2004 is what I think they’re using.
Common in these applications.

 

[Munkul]

I was going to just order the one from Express cutting and welding, but they have closed for Christmas this afternoon. I decided to take your advice and order 6 matching diodes from mouser, which I've just done.

There are two takeaways for people reading this thread.
1. Lorch machines (and other quality European built welders) are designed with repair in mind, not replacement.
2. Lorch dealers actually carry component level parts on the shelf. Think about this. I don't know any other brand dealers who do this.

Bottom line - the possibility of cost effective repair was the reason why this broken machine had any value to me at all. You wouldn't get that with a Chinese machine. Fingers crossed I've got the correct diagnosis, hopefully this welder will be up and running soon enough

 

[Jan-DIY]

Tbh Lorch never did repairs on component level.
On assembly level they did.

Btw these Mapro often failed in primary smps section.

I repaired 4 or 5 of them on component level.

Lorch offered a new mapro for about 1300€ which was a financial no go for the guys they send them to me.

 

[Munkul]

New diodes fitted today.
Powered up. No error codes. Yay!
However, it thinks its in remote/pedal mode and won't adjust primary amps, in tig or stick modes.
Funnily enough, i plugged my lorch pedal in, and it does actually adjust the amps that way.
I think it might be related to the tweco torch/remote wiring and possibly needs a torch plug plugged in, which i don't have just now (its an esab/tweco torch plug, not lorch)

I will do some digging.

 

[Jan-DIY]

Do a factory reset first.

 

[Munkul]

Cheers, i did try that but no joy.

I've managed to get it to work by shorting the wiper to pot minimum on the front torch connection socket. Welder works great, no issues
However, i plugged my lorch foot pedal back in, and i am unable to set a min/max amps at all, it just starts at 5 amps, and tops out at 25 amps.

Is this because of the tweco/thermal arc/esab foot pedal control logic? Does it need a bigger/smaller resistance pot to get the full range?

The welder works perfectly though, tested all the way up to 300 amps.

 

[Munkul]

I've had a look at the ESAB manual for the Arcmaster 301 AC/DC and I think it sheds some light on my issue.

Foot Control Operation
The foot control listed above Part Number W4013200 foot control will allow you to adjust the maximum output preset amperage. Other 8
pin remote's used with some of our other welders will function as below.
Press the foot pedal to start the machine output functions. The foot control potentiometer controls the welding current up to the level set
on the welding power source. Note that the maximum current must be set on the power source by the operator prior to the foot control
being connected. With the foot control connected, the power source will only display minimum preview Amps until the foot control is
depressed then it displays actual welding current when welding. Pressing the pedal to increases the welding current; letting up on the
pedal decreases the welding current. Releasing the pedal completely extinguishes the arc and initiates the post-flow shielding gas timer
(where fitted).
Note that some power sources may require the remote/local switch set to remote, the maximum setting of the power source will be
determined by the respective front panel control, irrespective of the remote control device setting. As an example, if the output current on
the power source front panel is set to 50% of the available current and the remote control device is set to 100% output or maximum, the
maximum achievable output from the unit will be 50%. Should 100% output be required, the respective front panel control must be set
to 100% or maximum, in which case the remote device will then be able to control between 1-100% output.

This would make sense, I had the main amps set around 25 amps before I plugged it in. Very silly arrangement.

The rear 14 pin connector works fine for the Lorch foot pedal, but it functions the same as the Esab/Tweco machines in that you're supposed to set a max amps, then plug a foot pedal in to the front 8 pin connector.

I'm used to the Lorch machines where you plug the pedal in the back, and you can use torch buttons, foot pedal and front panel controls all like normal, and set min/max etc on the panel no problem.

I assume I will need a jumper wire across the wiper to pot minimum on the front torch connection socket when I get a proper torch setup for it.

 

[Munkul]

Not sure if I should get a separate cooler etc for the tweco, or mount the tweco on the esseti cooler and build a smaller mobile cooler for the handytig.