EWM Picotig 180 welder- Schematics anyone?

[TheD312]

Hello guys,

I`ve rescently bought a defective EWM tig welder (for the Germans out here this should be a known name  ) for next to nothing. It´s parts are "hangin around in the breeze", therefore it seems that all the parts are there except for the most important thing.

It is missing the front panel. A example in this link:

http://www.ewm-russia.ru/upload/iblock/f46/PICOTIG_180-60.gif

As you can see it is just a plate with a encoder, few buttons, leds and a 7 segment on it. However a ewm pats seller here in Germany wants to charge 190€ for such a spare part, so I thought maybe I could fabricobble one together for myself.

I already found a manual in which you can see the panel and a cable that connects it to the main control board (page 56):

https://www.ewm-group.com/de/ewm-data/partner-web/Betriebsanleitungen/099-002046-EW500.pdf

You can see that the flatband cable contains the power and encoder pins, however the terms "WR RD CS OE" are used. I red a little bit about this and it has something together with SRAM, however I do not have any experience with such a communication way.

So basically to built a front panel I would need to know the schematic and parts that are used in this welder.

Here is the question then:

Does anyone have some schematics for this welder? I would also apprechiate if someone of you that owns this welder could unscrew the Panel and sent some photos of the PCB, then I would kindof get an idea how things are connected to each other....

Maybe I will post some pictures of the good machine tomorrow.

Best greetings from Germany,

TheD

[ace1903]

I haven't such welder but I looked at the block schematics.
A and B are both channels from the encoder. WR RD CS and OE are probably for shift registers. There is CLK signal for shifting data.
I think that on the pcb should be pair of shift registers , one serial to parallel conversion for LEDs and one parallel to serial for the switches.
All components costs ~15 EUR so it is worth to try to fix it.

I would like to see how well it is made and pictures from power switching elements.

[TheD312]

Hey,

Thx for the answer.

Yea I will post some pictures. This will be a "fun" restoration project, the welder is really in bad condition and I really am a big EWM fan.

I will look up some tipical applications for shift registers to think how it all works.

[TheD312]

So here is the little puppy, a made a few photos of the parts, I noticed that it really only misses the Front panel and some small things but not more than that. It can all be fixed easily, so I think for 50 quit I made a good bargain.

I took a look at some of the circuitry and have to say that it is a very very simple and legit design.
The main inverter PCB has what looks like a H- bridge DC-DC converter. The big transformer you can see on the inverter board (I labled the pats in one picutre) is the main transformer. It primary is driven with a few power trannys and the secondary gets rectified with two diodes (so the sec is a normal winding with a center tap being - aka ground).

A second board is used to drive the HF ignition transformer and has a little of torch contol circuit.

There is only one main board that controls everything, most of it is SMD and the main control chip is covered in epoxy, so sadly I can`t tell what chip they have used.

There is also some things the manufacturer did nice. Like that shunt built in to the outut connection or a "quick and easy" amphenol plug adapter 

I will clean the good boy up, rebent the back panel and try to get it up and running.

I just have no idea how to start builting that front panel thing.

This is something for the digital guys here, not really for me. I will measure out the dimmentons and make a custon front panel out of sheet metal with a foil screen in front of it, I will also plan to make a PCB beind the front panel with all the digital stuff.

I would really apprechiate if anyone could give me just a little idea how it all works. Or upload the schematics of the machine if you have one.


I actually put the photos to dropbox because here they will be either to big or jpeg.

Here is a link:

https://www.dropbox.com/sh/frzw6ly8nawbvq0/AACBDljilQTdvQ1esUnu7H2Ia?dl=0

[ace1903]

Before making any design is better to check if unit gives signs of life.
Is it possible to make spot weld using default settings without entering current with encoder?
Does valve clicks when switch is activated on welding torch?
I have never used this kind of welder but guess that hf part if working will produce spark.

Reverse engineering will be bit  difficult due to 7segment led.
First thing to do is to find voltage level for clock RD WR CS and OE.
Scope or logic analyser to find how many bits are shifted  in each sequence?
Any chance seller that asks 190EUR to provide you picture of the module that he/she sell?
Can you take better picture from main board especially around X4?
You can remove white label from the main chip using scalpel to remove epoxy just from the top of the chip.
I put my bet that it is STM32.
 

[TheD312]

I won`t really try welding with it first, I guess without the front panel it wont make any sence.

Here is what I came up with so far. The MCU is a STM UPSD3312D 8- Bit microcontroller.

I used my continuity tester of my multimeter to measure up where some important traces go.

The result is in the pictures. There is one important IC which seems to do some SPI to that RD CS... conversion, it does all the work but unfortunatly I wasn`t able to find any schematic of it at all.

Its part number is 89E77LK from Ti.

I also wrote some emails to random people who may have this welder asking for some photos. I don´t think the reseller would like to sent these....

I still do not have a scope so I can´t measure the signals.

[ace1903]

Based on my experience I think that marking is misinterpreted.
That's why I have asked for better resolution photo and close up from part around X4:
If it is like this
89E7
7LK
Then 89E7 is datecode and manufacturing place and 7LK should be SN74LS07.
I expect buffer/driver to be placed there.
Drawing with pencil are completely unreadable on the photo.

It is better to check for signs of life before spending hours on reverse engineering.

Where is ON button located? On missing board?