[dkmc]

I think this is my second post.
Although I signed up here about 2 years ago, I spend more time on the machine shop forums.
Mostly because that's what I do more of....machining.
But I have a welder/welding problem that's kicking my butt....
Here it is:

Machine: Airco AC/DC Heliwelder
Model: 2A/DDR-224 HPA/B-D
About 1972-1975 vintage.
Upright, Orange with Black top
I think it's actually made by Miller.

Mystery:
Again today I had some 304ss to tig weld.
Fired up the machine, and started welding, and I get a cold puddle,
have to really push the pedal down to add heat. Then I get a wide
large puddle that seems to not want to flow together.
When it does, it has a lot of heat in it and the HAZ is wide.
After it cools, the weld is gray and somewhat dirty looking, with
some minor black soot around it. Almost like there's not enough
shield gas. So I do about 10 1" long welds and am done, shut it
down.

Have to wire brush off the black soot and the gray from the weld.
Then I forget I did not do the other side...........SO......fire it all back up,
turn the welder, gas, and cooler back on.
SAME settings...and now it welds like a DIFFERENT MACHINE!
Small, narrow, hot puddle that flows real nice, and when done,
the weld itself is NOT gray and scaly, it is golden-rainbow colored
and CLEAN with a bit of brown soot around the much smaller HAZ.
The soot wipes off with my glove.

I cannot figure out what the HECK is going on with this machine!
It acts weird on AC and alu. as well, the molten puddle "vibrates" up and down.
And it seems like no ammount of current is enough to make the puddle
flow.........OR......there is a severely limited ammount of current available (but only when it's acting up).
A buddy that repairs welders came over and played with it a couple years back.......and we saw it seemed to weld OK.....on THAT day.

I can hear the gas coming out of the cup, and can adjust it for flow.
I do wonder if maybe the sol. valve is sticking or not opening all the
way. But.....it also seems like the actual output is different.
Like the amps are more or voltage is higher/lower...???
All I did was turn it off for about 5-7 minutes, then back on and it goes
from a POS to a great machine that makes nice welds.
It has ALWAYS been this way since I got it back in 83-84....
Some days crap, other days, nice effortless welding.

I am confounded as to what it could be.
I wish I had a flow meter of some
sort that I could put OVER the cup and check actual flow.
Is there such a device available?
What's next......??
A scope on the output??
At first it seems like it could just be a gas flow problem, but then it seems like it's the
current/voltage output.....or a combination of both.

Any ideas greatly appreciated!

dan k

EDIT
Well, I found a portable flow meter....
http://www.netwelding.com/MIG_Flow%20Rate-Chart.htm

[noddybrian]

Hi - welcome back ! there is a regular here with the same machine as yours so hopefully he will have some insight - I've no experience with one - but the fault reminds me of several large Mig sets I've looked at over the years with similar intermittent issues that were hard to pin down - in all cases they were 3phase & suffering from a loosing a phase some of the time - not always the same reason - but worth checking if your machine is 3phase - with something like this it's always worth getting someone else to look at the machine with the covers off while you weld - if possible in subdued light - very often its a bad joint somewhere & will visible spark when fault occurs - the other thing that's good is to use a cheap infra-red type temperature gun - use the welder for a while with the amps up high then go over it internally looking for any parts that are showing a different temperature from the rest of it - hope this helps or someone else is able to provide an answer.

[MinnesotaDave]

That's the same flow checker I have - works excellent.
After ruling out a gas flow problem I'd look electrical.

I'd agree with noddybrian - look for a loose connection - I'd start with the input cables and see if you are intermittently dropping one leg.

I'd also try a torch switch when it acts up to see if it's an intermittent problem with the foot control.
If you don't have one, set the amperage control to panel (or local) and leave the contactor switch on remote, then your pedal just acts as an on/off switch and does not control current.

When it is working correctly, check the OCV (open circuit voltage) at the studs and then between the torch and ground clamp.
Then when it acts up, check it again at the studs and the ends of the torch and ground clamp.
(Checking to see if the machine is still sending power but it's not getting through the cables)

When you weld at reduced power the HAZ gets larger because you are traveling too slow and cooking the material.

I know these are all really simple checks, but I like to do the simple stuff first.

Oh, and it's been doing this since the 80's ??? I'd last less than a week with a malfunctioning welder and then it would be outside on fire or sold to someone who could fix it.

[rick9345]

As Minnesota Dave says simple first

Start at incoming cables at Breaker box and loosen and reseat all eleclrical connections, all power cord and all the little studs and so forth inside welder right out through to torch head and pedal. Its a tune up.

Don't overlook clean reseat HF points

Like on battery cables that are dirty on a vehicle no start some times, but head lights come on, but starter draw kills circut,and then no start.

Eletrical connections oft over looked even on new welder problems.

[dkmc]

Thanks guys!
I will check all connections, and see how it goes.
Maybe pressure test the gas system to check for pin holes or cracks.

dk

[Otto Nobedder]

What concerns me here is the "ocillating puddle on AC" combined with the DC issues...

I think you may have a failed/shorted rectifier.

My first step would be a complete de-casing of the machine and blow out every inch of every circuit with dry/oil free compressed air, and see if it has any effect.

Steve S

[MinnesotaDave]

If your machine looks like my avatar, then I have a technical manual for it stored for download in dropbox.

https://www.dropbox.com/sh/7ijbgx67wuq6ivd/sYvAlvq_LC

[dkmc]

It does look just like that (only a lot cleaner ) and I do appreciate the link!

Thanks!
D

[MinnesotaDave]

It does look just like that (only a lot cleaner ) and I do appreciate the link!

Thanks!
D

That's the standard level of clean for all my machines

...and my truck...lol

[kiwi2wheels]

What concerns me here is the "ocillating puddle on AC" combined with the DC issues...

I think you may have a failed/shorted rectifier.

My first step would be a complete de-casing of the machine and blow out every inch of every circuit with dry/oil free compressed air, and see if it has any effect.

Steve S

Steve, do you use an additional regulator to drop the maximum pressure and do you use one of those multi orifice gun nozzles to avoid damage to small board components and windings insulation on transformer machines ?

I ask, because some places I've been that always seem to have problematic inverters ( who never blow them out......) claim that it's too risky. Thanks.

[dkmc]

No inverter in this old machine to worry about.....

[Otto Nobedder]

Steve, do you use an additional regulator to drop the maximum pressure and do you use one of those multi orifice gun nozzles to avoid damage to small board components and windings insulation on transformer machines ?

I ask, because some places I've been that always seem to have problematic inverters ( who never blow them out......) claim that it's too risky. Thanks.

I use line pressure through a large nozzle, held a few inches off the boards.

If the wind blows a component off, that was probably the problem (though that's never happened).

Steve S

[kiwi2wheels]

Thanks Steve.

[dkmc]

You can actually was down circuit boards with contact cleaner, then gently
blow than dry or let them air dry. Helps with getting the metal grit off of
them. There is specific cleaner for this.

[Braehill]

Dkmc,
I had similar problems with my Miller Dialarc 250 HF and finally one day a capacitor for the HF failed and I had to replace it. If I remember correctly it was about $80-90 online, works fine ever since. The good news is my welder has been very reliable so I don't know a lot about fixing it, but the capacitor was plug and play.

Len

[dkmc]

I did replace the caps in the HF years ago because the HF was weak.
The new ones didn't make a heck of a difference.
But I do not believe that is the problem causing the weird (intermittent) weld problems.

[kiwi2wheels]

You can actually was down circuit boards with contact cleaner, then gently
blow than dry or let them air dry. Helps with getting the metal grit off of
them. There is specific cleaner for this.

Thanks dkmc.

[dkmc]

To take it one step further if you're after increased protection, there is a
spray clear Circuit Board Lacquer that you can apply a couple thin coats of
that does help prevent shorts from metal dust and corrosion from moisture
and high humidity. Available from places like Didikey, Newark Electronics,
Mouser, etc. Maybe the modern welding machines have factory dipped boards,
I don't know....Or maybe they'd just as soon sell a replacement board instead??

I had a power supply in a CNC control that would act weird on power up if it sat in the damp shop
for several weeks of no use. I washed down the PB board in it, dried it WELL with a blow drier
and then put on 2 light coats of Lacquer (both sides of the board). To this day (about 3 years later)
the weirdness is GONE. Boots up flawlessly every time, even in the hot muggy summer months.