ESAB Smashweld 250 3-phase approx 1975? PC-board

[kaiser]

Hi.
I have an old ESAB SMASHWELD 250 which I would like to restore. The control board is not working, I assume the transistors have given up the ghost. The board has a number 34160-001A. There are 5 transistors on it, two of them are metal capped round units, that have corroded and the numbers cannot be read. They are placed in positions Q1 and Q2 on the board
If anyone would be able to put some values to these components or provide numbers, it would be fantastic.

https://imgur.com/rq5atzr component side
https://imgur.com/a/3p3KXFB track side

 

[Barking Mat]

Welcome mate, could be me, but your pictures don't seem to work.

 

[Seadog]

I'd say that your problem is more than likely the blown capacitor just below the relay. The orange block. I'd also look at the large orange electrolytic capacitor on the right. In a machine of that age it may well be failed or on the way out. Look for swelling of the canister.

 

[eddie49]

The control board is not working,

What is the fault, as exhibited by the machine as a whole? Have you done any troubleshooting of that fault that has led you to suspect the PCB?

 

[kaiser]

Some caps are gone as well, you are right, but there i can read the values. The small rectangular caps are cracked, (more than swollen).
My problem is with the components where I can't establish the values.

 

[kaiser]

What is the fault, as exhibited by the machine as a whole? Have you done any troubleshooting of that fault that has led you to suspect the PCB?

The machine did not respond when applying 380V. The fan was cut out, and I had to take the whole thing apart, because I can see broken caps and botched wiring. The thing needs a total rebuilt. And you almost have to take the whole machine apart to get to the board, so I want it right, when it goes back in!
I am only doing this, because I think these are excellent small welders, and I remember using one years ago, and it was smooth and nice to weld with. I also think the design, and it's extreme compactness is attractive. I know it is not worth the effort to restore it, but I am going to do it anyway! Provided I can get the board working!

 

[kaiser]

Welcome mate, could be me, but your pictures don't seem to work.

I tried to imbed the pictures, but it only shows IMG so I provided a link to IMGUR, where i uploaded the pics.
Here are some more, let's see if I can get this to work!
https://imgur.com/kxlDvcO
https://imgur.com/N0AyypK
No, not much success it seems!

 

[Seadog]

Upload the images to the post, not another host. Bottom right of your screen next to the "Reply" radio button.

 

[eddie49]

The links to all four of your photos ( both sides of the PCB, the wirefeed assembly, the front panel ) on Imgur work for me.
That machine has been through the wars! It is really rusty all over. Worth restoring though, good luck with it. Looks like it has 10 power ranges, two selections of inductance, and a Spot timer.

If you cannot identify the transistors, and if we can't source a circuit diagram for the PCB, then I'd suggest carefully removing each transistor in turn and using the Diode Test function to check collector-emitter high res both ways, then base-emitter and base-collector diode function. If OK, put them back.

 

[500e]

 

[Bobbes]

Is it this board?

 

[kaiser]

It is indeed that one! The only difference I can see is the number. Mine is number 341601 - 001A, so maybe the earliest version. As far as i can see the lay-out and the components look identical!
And of course a thanks for all the advice. Now even the pictures work as intended!

 

[Bobbes]

That number you gave is a factory number from a board without components. A pc board complete ends mostly at --- --- 880.

 

[kaiser]

Welcome mate, could be me, but your pictures don't seem to work.

While I searched the net for information, I came across this forum. I wanted to join and put my name and email address in, and it came back that the name and email address must be unique! So I must actually have signed up quite a while back, and never posted, and I forgot all about it.
Anyway, seems like a super forum for anything to do with welding! So I am glad I have now made the jump! And thanks for the welcome.

 

[Bobbes]

Herewith the partslist of your board. You see the number of your board without components in the list with the parts.

 

[kaiser]

OK. That could be it, my number is on the back of the card.
This is the board then, no doubt about it.

 

[kaiser]

Sir, I owe you one!
Thank you.

 

[kaiser]

Phew!! 4 years! anyway, an update. I started with this machine 4 years ago, and stripped and painted the unit, the paint I used was a beautiful green I had on the shelf, and a two pack at that. It turned out that the mix took months to cure, the hardener was either not effective or used too sparingly! So the nice paintwork was ruined as dust settled in the paint and it stuck to anything that came close. Shortly, not very successful!!
Then Putin eradicated Covid, and I got busy on other stuff!
This year I started looking at the machine again. The paintwork has now dried to the extent, that the parts can be handled, and I thought I better get my PC board found, and get on with it.
And then I could not find the board! I thought and thought, and then phoned a friend and asked him if I had given it to him. I had! (it was an act of desperation, I had completely forgotten!!) I got it back, he had not had time to do anything, and I then took it with me to Europe. While there I posted it to Boppes (the guy who gave me all the information in the thread above). He lives in Holland, and he fixed the board and I now have it again. Upon my return I started to work on the unit, and I cleaned up, traced wires and connected the board. It has twenty wires going to it. Most of them are black, but with a tiny number somewhere on the casing. I got most of the machine put together. It is a very compact unit, in fact so compact, that the wire roll cannot be housed in the casing, half of the spool protrude above the machine, and it has a small band of heavy cloth lying on top of the roll to keep the wire free of rust and dust. I decided to make it even more compact, and cut off almost the whole bottle tray at the back. I prefer to have a long gas pipe, and leave the bottle chained to the wall. We mainly have huge bottles here, and they are about 1.6 meters and weigh I guess 70 kg. A bottle like that strapped to the back of a small machine is asking for trouble. Trouble I can well do without!
So everything got connected and checked and double checked. Then I switched the power (380V) on, ready to switch off again in a jiffy if anything should bang, smoke or burn. Absolutely nothing happened. then I switched the machine itself on, still nothing. The fan is not yet connected and there is no pilot light. Then I bridged the trigger points on the euro connector, and the contactor and relay clicked in, and the motor turned!! Success!!
For about half a rotation, then it stopped. I thought I had burned something or connected something wrongly, and switched off again. Halfway disappointed but also greatly relieved that nothing had ended in a mighty bang.
I switched on again, the motor did not move, although the relay and contactor activated. No movement on the motor. I switched off, inspected everything for heat or burns and found nothing.
I measured the voltage to the motor, and depending on the position of the potentiometer, I had between 3.5V and 17.5 Volts DC present. Yet the motor did not move. I took the motor out and connected it to a car battery. It ran perfectly! I put it back in the machine, nothing! Measured and I had voltage on the supply wires. Back to the battery, motor runs!, Then I took a wiper motor and connected to the machine. It ran and the speed was adjustable! So it was then clear that the motor had some sort of problem. I took it to pieces, cleaned all parts, oiled and greased it and checked wires and brushes. All seemed fine. Assembled it and tried again. Nothing. I took it to pieces once again and could find nothing. and it still did not work.
Yesterday evening I took it apart again, but left it lying on the table because the light got too bad to see properly in the evening. This morning I was hell bent. It had to be found. I measured each section of the commutator and found one that did not have proper connection. Taking my illuminated magnifying glass out I studied each section carefully.

BANG!! there it was. Each wire from the winding ends at the commutator, where a small copper plate is folded over the wire and pressed down on each section of the commutator. All these tabs were bent down and touching, except one, which had a gap of a fraction of a millimeter. I took a small hammer and gave it a tiny tap. the motor now works!

On the picture above, you can see the tiny gap below the copper tap.
I have beautiful control from lowest setting to highest.
Come to think about it, I think this machine has never worked properly. On higher voltage, the speed of the motor will most likely have provided enough energy to let the motor rotate past the non conductive segment of the commutator, but on low settings the motor would have stuck on that part. That also explains why I at times measured open circuit, when I tried to measure connectivity between plus and minus on the connection terminal.
that machine I got maybe twenty years ago from a chap that had it standing defective. I think it would have left the factory faulty!

But this is the story so far. When time permits, I will get on with it and report accordingly. This almost had me foxed. You start questioning everything and doubt your sanity!

And to Boppes. Thanks for the repair. Good service!

 

[kaiser]

Just a short update. I have fitted a fan, adjusted the wire feed path, assembled the casing and made a fresh earth. Took an old MIG 0.8mm roll and wound the outer rusted layer off. Fitted to machine and used an old 350 North torch. Looks a bit weird with the botched paint, but never judge a dog by it's looks!
WOW!!
Without gas, as a test. Crisp, smooth, even!! The wire feed is so easy it is just laughable, no fiddling, no stress.
I will give an update when I get gas unto the unit, but this is about the smoothest (?) I have ever seen, exactly as I remember.
Who needs an inverter when a well behaved transformer unit welds like this?
And this one, with a bit of luck will outlast me by decades!
An inverter would not!
Hat off to old school machines!!

 

[kaiser]

So, now I have the machine as I want it. I started welding with the unit after I got it going, but I was not happy with the amount of spatter I got. I tried all combinations of settings and was even considering trying another gas, but this gas works well on other machines, so I decided to take the machine apart again. This time the electrical connections to the rectifier, the transformer, the Dinse plugs etc etc. It has taken about 4 hours, each bolt and each connection has been sandpapered or cleaned with steel wool, and I have just tried the machine again. It is like night and day. Smooth and spatter can almost be eliminated now, by making sure the right earth outlet is selected together with the appropriate speed and power.
Perfect welding. Very happy. I will see if I can get a video made!

So my advice to anyone with an old machine you think should perform smoother. Clean all connections. If you can see one, clean it, and tighten it when assembling again. Real hard, without overdoing it.
It also gave me an opportunity to try out my new impact wrench with a battery, and I can only say it is a heaven sent, if you need to get a stubborn connection loosened. And far easier to bring to the job, compared to the pneumatic version, which is much more powerful, of course. So all in all, a fruitful morning!