EconoTIG information

[o.c.d.]

Hi guy's,

Today I purchased 2 Miller Econotig welders from a local welding supply for $200.00 each, one is a 2003 the other is a 1996. These units are supposed to be not working and in need of control board repair. I opened the units up and checked some components with a DMM and nothing appears to be shorted, but I have yet to plug either one in. I've wanted to try my hand at tig welding for a long time but never had the opportunity (or the money to purchase one) until I came across these units. So being green to TIG, I have a few questions for some of you more experienced people.

Is the EconoTIG a good machine for hobby type stuff? What are the pros/cons?

I have no shielding gas, I suppose that the arc start circuit could be faulty, at lease from what I've been reading on the internet. If I have no shielding gas will the welder still start an arc or is the gas necessary? I wanted to get the welders working before I go and buy a cylinder.

Does anyone have a detailed schematic of the control board?

[runchman]

You can get an arc w/o gas, but it won't weld for crap. But I can understand not worrying about the gas at this point...

- John

As a start I'd turn the beast on and see if you've got dc voltage to the control boards. i.e. start simple with the debug. Hopefully you know what you are doing with a dmm and won't electrocute yourself with the box open.

[Doolittle]

Make sure your breakers been excersized a little (snap it off and on a couple of times to make sure its limbered up). Go ahead and measure the resistance across the plug terminals (hots) and see if youve gotta dead short across the primary, or an open, make sure the on switch is on but unpluged!! (possible fuse, relay just dont know how they power these things up yet). Flip the switch back off..

Make sure your wire is beefy and Id use a lower current breaker than whats recommended just in case..

Plug it in.

I would try and put the amps at say, 10 stick mode, put my voltmeter lead directly on the tungston, electode holder or in the socket and the other to ground (DO NOT TOUCH ANY METAL OR THE END OF THE LEADS!!). see what voltage you get. It may just be a remote (footpedal) problem, ac only etc. Of course if the smoke starts rolling shut it down. Have a fire extinguisher handy, wear some gloves. Diodes seem likely to fail in a welder, so perhaps in the rectifier something went 'poof'? These have gotta be huge.

Wait a minute.. Heres a link that might work..

http://www.millerwelds.com/om/o303t_mil.pdf Goto page 22

It just shows the main power circuit, but definately put it on stick mode, you can leave the tig torch hooked up, or simply measure between the output terminals. Looks like thats the straightest shot through the maze.. That contactor (relay? magnetic switch?) looks suspicious.

Even miller probably replaces the board if it fails it looks to have a 2amp fuse somewhere, its gotta be for the control board. Replace it, if it blows right away, Id just get a new board. Maybe you have this info allready?

Whew, sorry about the ramble. The schematic is lacking mucho detail. But...

It looks to me that in stick mode, it bypasses the control logic. The 'contactor' maybe the amperage control but it also makes sense that the control turns a switch on to make the output hot. Give it try. (If you measure a voltage, try striking an arc with stick).

I do believe the only way to get anymore detailed on schematics, will be to contact miller. I here their customer support is top notch.. Perhaps they can tell you what the voltages are supposed to be at those mysterious test points...

As stated, Im no welder repairman, so take my advice for what it is. AND BE CAREFUL!

[o.c.d.]

Thanks for the information..

I've been repairing electronic equipment all my life so the control board poses little difficulty in regard to its repair.

Here's what I've found so far. Both welders power up and output either AC or DC + - depending on the control setting. I have no gas but it appears that using the TIG wand on a 16 gauge piece of steel burns through the tungston electrode almost as fast as the sheet of steel. I don't thinks this is normal. Possible the control circuit is wide open?? Both units do this regardless of how far the pedal is pressed. I guess I'll start ohming out the control pots and connect my oscope up to see if the control board is indeed pulsing the transformer.

[Brand X]

Get some gas before you go any farther. Without shielding gas that is exactly what happens.

[o.c.d.]

Thanks Brand X,

I dug up my old Richard Finch books looking to see of the sheilding gas adds cooling to the tungsten, have not gotten that far yet. I don't know what type of tungsten these 2 torches have but I started out with a sharp point on one and within seconds it was flat. Does that sound like what no gas would do? This particular torch was a weldcraft with 1/16 tungsten.

[WelderDaddy]

I bought a used 1994 econotig recently and it works but in DCEN mode it just puts out max amps regardless of pedal or front dial position. It will just get the 1/16 tungsten red hot even with gas flow. Miller technical service said that it is the circuit board since there is really nothing else in there for the current control that is not on the board. A new board is $450.

Im sure where you got these from were aware the board was out since they sold them so cheap. Seems to be a common problem?

You can check your foot control and front dial resistance with the DMM as well as the OCV (78 volts) with the machine on. Mine checked out OK on these. Hence probably the board.

[Doolittle]

Yep, thats what will happen on 1/16 especially. The gas shields the tungsten from the atmosphere, it may provide a little cooling effect, but the tungsten in itself has a super high melting point (pretty cool stuff). The argon also protects the molten puddle in the same way(I think from what ive read that Hydrogen is the big no no). I do know this, if you do not let the gas line purge out air, the beginning of your weld will suffer. You can use Helium or argon or a mix (read something about argon/hydrogen too). I think all of us use argon, it works well and is much cheaper and easier to find than helium.

Ive got a degree but rarely have I used my board repair skills since I fixed typewriters in late 80's, early 90's. I work for a manufacturer in field service work and even we cant get detailed schematics.. The world is changing. Sorry I was so basic, just didnt know your skill level ( I was imagineing someone who got a DMM for christmas and decided he could tackle welding repair as a hobby). Anyway, sounds like youve got working machines. Did they have a foot pedal with em? They control current 'remotely'. They will work without it, but it makes for better welding with one.

[Doolittle]

Does this board have any asics? Is it smt stuff? If its a common problem then its probably a common component on that board.

[o.c.d.]

WelderDaddy,

You hit it on the head. After reading my welding books I realised that the polarity needs to be - on the torch to direct heat to the work piece. I have 2 of these, oddly enough the newer one 2003 appears to work fine. The other one 1996 with the weldcraft torch 1/16th EATS the tungsten right away. I ohmed the foot control and the front panel pot and compaired to the "working" one. I then swap the control boardf and now the 1996 one works without burning a hole through the 16gauge sheet or melting the tungsten like a cannon fuse. I found a schematic here but I think it's for the older style board ( I have it also as it came with the second welder) the welder it self had the newer style board installed. So... I guess I'll start compairing one to the other to detertmine which part is bad. I'll let you know what I find.

I kinda screwed myself because I was too cheap to come up with the 400 bucks myself for the 2 so I talked a friend into doing half, now I've got to repair this thing come hell or high water or I'll have a 200 dollar boat anchor.

[o.c.d.]

Hey Doolittle,

The board is very basic no ASIC or SMC, just a nasty coating to protect the pcb and components. This darn thing, the bad board has identical SCR gate waveforms as the working board, but I have not checked the voltage yet. I hope I can find a schematic that matches the newer style board, in the mean time I going to check all the usual suspect components first with the DMM.

No big deal, I hear the same thing all the time as well. I started out repairing cars and lawnmowers in south Alabama when I was in the 8th grade, went on to repair tv's and vcr's through late high school. Now I'm a senior staff engineer for a major electronics manufacturer.

[Doolittle]

Cool man! Always wanted a job like that, got stuck doing this stuff now.. Its actually pretty fun and relaxed though, no boss hangin over my shoulder, travel around all day.

Just allways pictured myself being a QA tech since I love making things fail..heheh.

To see the engineers cringe when they hand me a prototype (maniacal laughter!)

After all these years of fixing their crap they wouldnt stand a chance now.
Anyhow, I kinda figured it would be a simple robust design, they potted the board!! ahhhh!!! How in the heck you gonna get that gunk off it?

Its probably one of those scr's then (shorted inside so it doesnt give a darn whats coming in the gate). Used to have those fail on heater circuits and either 1. pop clixon (thermal breaker) or 2. Weld itself to the plate it was mounted too of course, we replaced the board... Ours were controlled through an opto isolator from 12volts coming off the main pcb. The newer stuff is way more reliable.

So its just pulsing the output (duty cycle) to control current flow then ahh, now it comes together, thats what the output transformer is for! it smooths it out huh? just curious. I figured they got away from big variacs and VR's on these things.

That little bit I saw kinda looked like a tube amplifier speaker output.

Anyway, good luck man, youve got the schematic which is more than I can say... Let us know how it comes out. There will be alot of people interested in the fix (I see broken econotigs being scarfed up off ebay in droves)...

[o.c.d.]

Got it fixed! Thanks for all the information, you guy's are the best around.

Miller was kind enough to send a manual via email that covered schematics, waveforms, and a troubleshooting guide for the newer Econotig SN KD502157 and up, my welder already had the controller board upgraded some time before I got it. Regardless the manual works on either early or late models, but only has a schematic for the newer style controller card.

Here's what I did. Knowing that I had to get parts I decided to go for broke and replace most all in the shunt winding control circuit, most likely the only thing needing replacement was the main SCR (Q13), but what the hell. I live north of Dallas and know of a real cheap electronics surplus place. After $18.65 I get home and replace the following on the controller;

D22 1N4749A
D20 and D21 1N5062
Q13 S8055M
Q11 IRFD110
OC1 4N32
OC2 H11C1

Plug the board back in and try once again on the 1/16 tungsten torch. Now the tungsten burns down what I think fast but I have no gas, the other torch is a miller with a 3/32 tungsten it last quite a but longer than the 1/16th, and will maintain a point.

Now more questions for you experts out there.

I'll be welding mostly mild steel ~ 16gauge or larger (only hobby style stuff, 1 hour a week at most), what type of gas and what size cylinder should I buy? Anyone have any ideas of who would be the cheapest? I use Praxair for my O.A. but could change in a heartbeat.

Given the metal I'll usually be welding what tungsten is best the 1/16th or 3/32nd?

I will at some point like to weld aluminum do I have to use helium for this?

I'm afraid that the Econotig may be too heavy duty for what I would like to do, although the label says "DCEN 18 gauge should be easy", not ever using a tig welder before what do ya'll think?

[WelderDaddy]

Hey o.c.d

Can you email me the info Miller sent you on the schematics, waveforms and troubleshooting. I just have the basic owners manual off the Miller website.

my email is: hanson@engr.uky.edu

Thanks

[Brand X]

Generally the larger the bottle the cheaper the gas. It's a labor issue on filling
the bottles. If you could swing a 150 CF that should be a good size. Just use
100 % argon to start out with. 3/32 will be a good size tungsten for that machine.

The econo-tig will be a very nice unit to learn with. Aluminum it's down in
duty-cycle for anything thicker then .125 but it will work on somewhat thicker
stuff with preheat. The torch gets really hot on AC, but DC output you will be
fine. I would probably order some 3/32 blue tungstens off of e-bay to start.
Brown zirc. will work really well on ac, along with red Thoriated 2% on dc.
The blue will do both just fine. I used that combo on a Lincoln 185 the other
day and you can ball the tungsten for your ac work. You will want to do that
because a sharp point like you use for DC, does not work very well on those
type machines.

Have fun.

[o.c.d.]

WelderDaddy,

I forwarded the manual to you. Let me know if you don't get it.

BrandX,

Thanks for the information. To clarify, 3/32 blue tungsten (I guess just "Blue Tungsten" will be the correct thing?), for all mild steel use 100% Argon? Do I have to have Helium for aluminum?

Thanks for the information. My Finch book doen not go into any major detail, or maybe I need to read it again.

[Brand X]

Do I have to have Helium for aluminum?


No just argon because it works fine. If you need more heat for thicker stuff
then and some Helium to the mix. You will want argon for your dc work anyway.
If you are doing a lot of aluminum over .125, get a bigger machine. You could
try a mixed helium gas to help but it's probably a stop gap measure with the
machine. Duty-cycle is really low for much aluminum work. The starts kill the
duty-cycle because it takes too long to get the puddle wet. 200 amps on a
standard tig machine really helps get the puddle wet fast. Anything less
is alway somewhat of a struggle. The air cooled torch will get red hot on
that type of machine too. A inverter type machine can overcome most
of those problems because it spends way more time on the dc side.
That means more heat into the work and less into the torch.

Just learn and enjoy what you have. Also buy a thick glove for your
torch hand, when running on ac output.:)

[Doolittle]

Idunno, thats a pretty nice 220 dollar tig welder. And, you can fix it! heh.

Congratulations, and welcome to the wonderful world of welding...

See if you can find some 3/16 mild or thinner mild steel and some 1/8 sheet aluminum to play on. 3/32 is plenty big for this stuff and follow the other guys advice on the type of tungsten to use.. Heres a little spec sheet on types of tungsten.

[o.c.d.]

Thanks Brand X,

I found the blue Tungsten you were refering to, according to
Miller it looks to be the best on most anything except Aluminum. Already have some nice gloves that I use with my wire welder and O/A torch. Now I just have to come up with a couple hundred more dollars for Argon and tank, damn this hobby is expensive.

[Brand X]

The Brown stripe zirconiated will be the best for Aluminum with your machine.
It's about 5 times the cost for very little improvement on your machine. The
blue lanthanated is a pretty good overall tungsten for Rec. transformer machine or inverters.

http://www.aglevtech.com/LANTHANATED_Tungsten.html

[Doolittle]

The Brown stripe zirconiated will be the best for Aluminum with your machine.
It's about 5 times the cost for very little improvement on your machine. The
blue lanthanated is a pretty good overall tungsten for Rec. transformer machine or inverters.

http://www.aglevtech.com/LANTHANATED_Tungsten.html
Those are some good prices!

Is the 2% any better than 1.5% lanthanated?

[runchman]

I bought my lanthated from that aglvletech guy off ebay. Fast service, I'd recommend him.

- John

[Brand X]

Those are some good prices!

Is the 2% any better than 1.5% lanthanated?

I used the 1% black quite a while ago, and did not care for it.
I skipped the gold 1.5% and went straight to the blue. I used
it on a Dynasty 200, Lincoln 205 T and my machines,Thermal
prowave GTSW, TSW 300 and now the 185 arcmaster I own.
It holds it's pointed shape at higher current outputs. I still like
the lowly 2% red for the shape of the arc cone. The 4%
thoriated or orange has my interest up. I have a orange 3/32
that works really nice but I am not sure if it's ceriated or
the 4% ? It could be either.

[runchman]

Well now I'm going to have to buy some of the lowly 2% red and give them a try. My only experience is with the 2% lanthanated, and pencil leads er I mean harbor freight tungstens.

- John

[ss42768]

The orange is 2% ceriated, and will work well on aluminum, stainless and mild steel. Grind it to a point.

[Brand X]

The orange is 2% ceriated, and will work well on aluminum, stainless and mild steel. Grind it to a point.

Overseas, orange could be 4% thoriated.
I probably have ceriated but I can't remember
where I got the lone tungsten I have. The
econotig will not really like a sharpened
tungsten for ac work. Inverters thrive on
them.

[ss42768]

I'm not sure how the 2% ceriated will perform on the Econotig, but I've got two customers that build aerial platforms for fire trucks. Both use 2% ceriated on Syncrowave 350LX machines, which is a trans rec unit. Both operators have told me "Where's this stuff been all my life" as they really like how it performs.

___________________

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