Welding issues

[George Dennis]

Hi, I've a new to me welder, the previous owner (family member) brought it many years ago and didn't got on with it so brought a bigger and better one,
I thought I'd give a try out with basic welding and found that it arcs up only for a few seconds and then peter's out, this happens every time I try and use it, I'm fairly new to welding but have used my dad's cebora mono welder many times with no issues.
Would anyone have any ideas what could could be wrong and how to fix it
Many thanks

 

[Mark 2]

2 or 3 seconds is a long time in the welding process. Are the rods dry, they have a damp 1970s look about them? Rather like Chris Tarrant.

 

[BrokenBiker]

how deep into mid wales are you? id be inclined to bump the amps up...you havent really got any way of knowing if that dial is accurate. id bump it up to the max, try again, if it seems way too hot bring it down til it feels right and then see what setting it is on.

also, as above, those rods look older than me so possibly they could be the issue, stick one to the work for a few seconds to cook any moisture out then yank it free, as if you got it stuck while trying to start an arc...then try again and see if that makes any difference...it has a pretty poor duty cycle too, although 30%ish at 50 amps is more than enough from small stick welding jobs its something to keep in mind when purposely sticking rods to cook them dry, could easilly hit the overload

 

[George Dennis]

I've tried different rods with it and found the rods act in the same way, the acrs strikes , fairly weekly and then fizzles out, I've tried the same rods on my bigger welder for a while warning it up, and it works fine, then put the same rod back on this smaller welder and it does exactly same as before?

I'm in newtown powys mid Wales are you close by brokenbike,

 

[BrokenBiker]

I've tried different rods with it and found the rods act in the same way, the acrs strikes , fairly weekly and then fizzles out, I've tried the same rods on my bigger welder for a while warning it up, and it works fine, then put the same rod back on this smaller welder and it does exactly same as before?

I'm in newtown powys mid Wales are you close by brokenbike,

not exactly close, im in newport, south wales...if you were closer to brecon id call it close.

if the rods are known good rods then my only real suggestion is to crank the little welder up more and try again...my little fall back buzz box needs to be set at a supposed flat out 90 amps to light a 2.5mm rod that usualy runs at 70 on my inverter

 

[George Dennis]

I've turned it up to max and and it still does the same, it strikes up but weakly and fizzles out? It's a strange one?

 

[BrokenBiker]

I've turned it up to max and and it still does the same, it strikes up but weakly and fizzles out? It's a strange one?

are they 6013 rods?

have you got a multimeter?

pull the torch and return leads out, flick the machine on and test the DC voltage across the 2 sockets, it sounds a bit like it could be voltage related and a low OCV may be the cause although id expect that to make it hard to start but then start lit

 

[George Dennis]

I'll have a look tomorrow ( night shift starting soon )at the rods, I can't remember what whey are, I'll dig a few others out and try, I do have a multimeter but not not sure of the settings I'd need to test it?
Thank you for the advice so far helping with this

 

[BrokenBiker]

I'll have a look tomorrow ( night shift starting soon )at the rods, I can't remember what whey are, I'll dig a few others out and try, I do have a multimeter but not not sure of the settings I'd need to test it?
Thank you for the advice so far helping with this
View attachment 515622

turn the dial on the meter 2 clicks left, that will test anything up to 200V DC. the leads are in the correct sockets so just stick the black in the - and red in the + on the welder, and keep your fingers clear.

see what number it spits out. you want between 40-50 for 6013 rods, higher for something like a 7018 wanting around 60V or more. generally the higher the better, but im not expecting much from a little welder like that, so anything above 40 should verify the welder has the OCV to run the rods

 

[George Dennis]

Right just had a quick check the first reading Set it to 45 amp which read

The second reading was on the full 90 amp

I have work now I'll get back asap for any other checks

 

[BrokenBiker]

thats a lot higher than i was expecting...could indicate a fault, maybe not. but if thats the true OCV of the welder then it should run pretty much any rod

 

[jo1010]

That OCV between different settings should show a change - you have a machine problem - has it been stored in a shed maybe?

Damp rods also give the symptom you have .....Baking in the oven for 20 minutes at around 150 C....that will get the moisture out of them.....

 

[eddie49]

Checking the OCV of an inverter welder actually is not very meaningful. They typically show from about 60 volts upwards. This value applies to MIG welders as well as Arc ( MMA ) inverter welders, and of course traditional transformer-based MIG welders actually run at 15 to 30 volts. The output waveform of an inverter is not pure DC either, which will confuse a digital voltmeter. The only meaningful voltage tests would be under load, when the voltage or current feedback circuits are actively controlling the pulse-width modulated signals that drive the inverter power electronics.

I suspect that the current feedback control of this inverter Arc welder has failed.

 

[eddie49]

This thread describes the repair of an inverter welder that had a faulty current measuring sensor:

Thread 'SIP HG2500P AC DC Tig Control board bad?'

Aug 11, 2023

I spotted this £1100 odd RRP welder on FB marketplace this week for £150 as spares or repair. Phoned seller, nice guy and said it started to give trouble and with his work he had to buy another welder to keep him going and that was a few months back.

He did then take it to a repair guy and he had it for about 4 months but kept ignoring him and he ended up landing and collecting it back off him. What he did say was the repair guys parting comment was that it needed a control panel at about £100.

I then bought it for £150 including the leads etc.




First...

• JOEPRO
• Replies: 25
• forum: SIP & Cosmo

As shown in Post #23, the sensor is typically a square plastic block surrounding one of the two heavy current output cables, inside the welder. It provides an output that is proportional to the current flowing in the cable, and this signal is used to hold the arc current constant at the set value as the load increases. Arc welding requires a constant current ( CC ) power source.
Rather than the sensor, the fault could also be the control circuit on the main board.
It is also possible that the current feedback has no effect because a major fault in the inverter power source is preventing it from delivering adequate power.

Tec-Arc in York offer to repair any make of inverter welder.

 

[George Dennis]

Sorry the delay getting back the joys of working nights,
This morning I put several different rods in the oven as suggested for 45 mins to make sure they were fully dry,
I've tried again to get this to work with the same results a few sparks and the rod sticks but unable to strike up a continuous arc to weld with,
The history of the welder briefly is, a family member who owns a engineering firm brought it for something portable. but found it to small for their needs and never really used it , so it's sat in a cupboard , the past 15 years, PAT test says 2010 so I'm presuming , it was put in a cupboard before then? Company closed recently and it was passed on to me.
I'm all for opening the welder up with some guidance on what to look for and test would be greatly appreciated
I've put picture of the welds I've tried, the rods are in anti clockwise order

 

[chrismac]

I had the same issue with a eutectic power max 2, it was repairable just not by me, sold it on for scrap price.

 

[eddie49]

You could open the welder and look for loose connections. If a joint on the high-current path was loose, that would explain the lack of power to maintain an arc.
Start by disconnecting the machine from the mains and waiting an hour or two for the capacitors ( with up to 325v DC ) to safely discharge. Then remove the covers and check for:
- loose push-on spade tags at the back of the mains power switch and on the bridge rectifier ( a rectangular alloy block mounted on a heatsink, with 4 tags, - there may be two rectifiers in parallel )
- loose bolted connections on heavy internal cables and copper or aluminium busbars, at heatsinks, and on thick tracks on the PCBs, and at the back of the front panel Dinse sockets.
- loose or poorly-seated plugs on the multi-wire harnesses between the PCBs
- any sign of blackened or burnt components, especially the multiple paralleled power semiconductors ( MOSFETs, IGBTs, and diodes ) that will be attached to the large finned heatsinks.

In imported inverter welders I have found push-on tags that were barely seated, and bolted joints that were just finger tight.

If you are confident working on live equipment, measure the DC output from the bridge rectifier(s). It should be about 325v DC. After smoothing by the large electrolytic capacitors, it is this DC bus that runs the machine.
**Do not do this if you have any doubt at all about working safely on live circuits!! The high voltages, the charge held in the capacitors, and the DC aspect make inverter welders very dangerous.