Hede Nielsen mig welder

[Martini]

I have been using a Hede Nielsen Mig welder on and off for about twenty years. Suddenly it has started burning holes through 1.0/1.2 mm steel sheet when on its lowest setting. The arc looks and sounds more fierce than it used to. Any suggestions as to what has changed? Everything inside looks and feels ok (connections, switches etc) It has three large capacitors. Could one or more of these failing cause this?
All suggestions welcome as I either need to fix it or buy a new welder.

 

[anto]

Is it a gas or gasless welder?
If its a gas welder then it sounds like you've run out of gas.
If its gasless then I don't know.

 

[mike 109444]

If caps not working then there would be LESS punch and your welds would be building up and lacking penetration.
You might need to set machine to lowest setting and back off/flip off wire feed, then meter between the work ground clamp and the weld tip (meter set to DC volts) and see what voltage you are getting. Maybe step up through the range and note the readings.
Could be you have a duff diode that's passing SOME AC through.

 

[mike 109444]

Oh and welcome BTW

 

[Martini]

Thanks guys.
Welder is a Hede Nielsen Euroboy 3. which I bought new many years ago.
Gas Pressure gauges show ok and I can hear gas release.
Capacitors all look good and it is good to know that they should not cause this type of fault.
I will try to test the diodes to see if any have broken down.
Welder has 4 power settings and is working fine apart from arc is too fierce even on lowest setting.
I will try some voltage measurements.

 

[Martini]

Small update. Stripped out diode pack. 8 diodes on as 4 pairs on heat sink grid. All diodes test ok.
Will take capacitor bank out next

 

[Martini]

Update:
I have removed capacitor bank. Three 16000 uF capacitors in parallel which I presume add up to 48000 uF.
Tested each capacitor with ohm meter. Two test as open circuit and show changing values as they try to charge.
One fluctuates between open and short circuit. Retested all three with power supply and bulb discharge. Two will charge and discharge, the third will not.
I bought 3 x 15000 uF capacitors from RS components and fitted them. Welder is once again ok with thin metal. So it seems that the smoothing from the capacitors is important in avoiding burn through of thin steel sheet. My guess is that one capacitor was failing by short circuit so effectively cancelling all of the capacitors. I have treated the welder to a new complete torch. I also purchased 4 new large diodes so at some point I will make a new diode bridge to try out.

 

[mike 109444]

Result and good on you for posting results back on here

 

[mickleaver]

ANY ONE GOT A SETTING SWITCH FOR A EUROBOY 15 WELDER

 

[eddie49]

Hello, and welcome to the Forum.
By "setting switch" I assume you mean the welding power range switch? These multi-position, multi-pole switches can be very hard to define and to source, especially one for this rare and obsolete Danish MIG.
Is the switch jammed or are the internal contacts burnt? Have you tried a spray with contact cleaner or WD40?
There may be a label on the switch with the manufacturer's name and a model number.
If you disconnect any of the wires, be sure to label them. It is generally not advised to try to open these switches, they tend to self-destruct if you do that.
How many positions does the switch have? Can you trace the wires that feed power in and select tappings to the transformer? If it is something simple like 1 pole 6-way, it should be easy to find a generic substitute.

 

[mickleaver]

THANK YOU FOR THE ADVISE MY SWITCH DOESN'T WORK ON NO2 NOT BAD GOING AS I'VE HAD IT 35 YEARS JUST HAD IT REPAIRED £350 CANNOT WELD 20 GAUGE PLATE WITHOUT BLOWING HOLES WERE CAN I GET A LOAD RESISTOR TO SUIT EUROBOY 15

 

[eddie49]

If only one setting of the power range switch does not work, it is probably caused by a burnt internal contact at that position. It is just possible that the transformer tapping wire for position 2 is simply loose at the screw terminal on the switch, or maybe that tapping wire has burnt out or fractured at or on the path to the transformer. Internal pictures of the switch area and transformer windings and tappings would help.
When you bought the machine 35 years ago, did it come with a manual, did that include a circuit diagram, and can you still find it ...!! ?

Repaired for 350 Pounds,,, wow.. you must be very attached to it...could get 2 new ones for that price !

I'm not sure what your plan is for a "load resistor", if you mean to reduce the welding power for thin plate - no, that won't work.

 

[mike 109444]

If Eddies suggestion does not fix it. A cheep (temp ) fix would be to disconnect position 1 wire from switch and insulate (and label it) and move position 2 wire to position 1.

 

[mickleaver]

If only one setting of the power range switch does not work, it is probably caused by a burnt internal contact at that position. It is just possible that the transformer tapping wire for position 2 is simply loose at the screw terminal on the switch, or maybe that tapping wire has burnt out or fractured at or on the path to the transformer. Internal pictures of the switch area and transformer windings and tappings would help.
When you bought the machine 35 years ago, did it come with a manual, did that include a circuit diagram, and can you still find it ...!! ?

Repaired for 350 Pounds,,, wow.. you must be very attached to it...could get 2 new ones for that price !

I'm not sure what your plan is for a "load resistor", if you mean to reduce the welding power for thin plate - no, that won't work.

 

[mickleaver]

EDDIE YES I'M VERY ATTACHED TO EURO BOY 15 THIS ONCE FINE WELDER IS NOW HARSH NOISY TO MUCH SPLATTER NOT THE MIG I KNOW BEEN TOLD A LOAD RESISTER WILL REDUCE THE POWER OTHER WISE £350 WASTED

 

[eddie49]

Using a resistor to drop the output voltage of a MIG welder is just not going to work. If the welder is putting out 30 volts DC and you want to drop that by 10 volts, then at a welding current of 30 Amps the poor resistor is going to have to absorb 300 Watts. It would melt.
If your very expensive repair job was recent, I would take the machine back to where that was done and demand they put it right.

Otherwise, we need to diagnose what has gone wrong. From the symptoms, it could be a short-circuit in one of the ( 4 ) diodes. They can be tested with an Ohmmeter, or a digital voltmeter ( DVM ) on the "Diode Test" range.

Another test is to check the voltage output: turn the gas off, slacken the pressure roller, connect the negative of a DC voltmeter to the Earth clamp and the positive to the tip of the MIG torch. Set the machine at the lowest power range, press the torch trigger. The meter should read about 15v DC. Go up to the next range, and repeat. You should see the voltage rise steadily as you step through the power settings, going from about 15v to maybe 30v at the top setting. Let us know what the results are.

 

[mickleaver]

Using a resistor to drop the output voltage of a MIG welder is just not going to work. If the welder is putting out 30 volts DC and you want to drop that by 10 volts, then at a welding current of 30 Amps the poor resistor is going to have to absorb 300 Watts. It would melt.
If your very expensive repair job was recent, I would take the machine back to where that was done and demand they put it right.

Otherwise, we need to diagnose what has gone wrong. From the symptoms, it could be a short-circuit in one of the ( 4 ) diodes. They can be tested with an Ohmmeter, or a digital voltmeter ( DVM ) on the "Diode Test" range.

Another test is to check the voltage output: turn the gas off, slacken the pressure roller, connect the negative of a DC voltmeter to the Earth clamp and the positive to the tip of the MIG torch. Set the machine at the lowest power range, press the torch trigger. The meter should read about 15v DC. Go up to the next range, and repeat. You should see the voltage rise steadily as you step through the power settings, going from about 15v to maybe 30v at the top setting. Let us know what the results are.

 

[mickleaver]

UNFORTUNATELY MY FRIEND IS A WELDER FABRICATOR WITH LIMITED KNOWLEDGE OF MIG SO HE SAID HE CANT CARRY OUT THE TEST YOU RECOMMEND NEED SOMEONE IN SOUTHEND AREA MANY THANKS FOR YOUR ADVISE

 

[slim_boy_fat]

Welcome aboard @mickleaver I'm afraid I can't help with your search, but please turn off your caps lock - it's construed as the equivalent of shouting, and thereby bad form.

 

[mickleaver]

Welcome aboard @mickleaver I'm afraid I can't help with your search, but please turn off your caps lock - it's construed as the equivalent of shouting, and thereby bad form.

THINK BEFORE YOU POST I'VE HAD TO OPS ON MY LEFT EYE AN CANT SEE SMALL PRINT