Need Help with Econotig Internals

[buffumjr]

I just bought a Miller Econotig. The stick (SMAW) settings work well. The TIG (GTAW) side has an issue. The foot pedal is supposed to regulate power. It seems that all it does is turn the gas on and off. I looked inside. Nothing is obviously burned. What should I look for, and how should I test? I have a digital volt meter and a good magnifying glass. I have a solder sucker, and have done circuit board soldering before.

MILLER MUST BRING BACK THE ECONOTIG! FOR BEGINNERS, A PHENOMINAL VALUE. FOR AUTO SHOPS, SAME.

[buffumjr]

What is the resistance and wattage of SUP1 and SUP2? Too badly burned to read the rings. Anything usually go bad with these?

[shovelon]

A couple things I would check before going into the machine. Check the resistance on the potentiometer inside foot control. Then continuity of all wires coming from the foot control. Then see if the microswitch in the foot control is tripping a relay inside the machine. If it does look for the contactor block that the relay should energize to start the power. Another problem could be the AC/DC switch. Sometimes the contacts are burned or the switch is not fully engaged.

Good luck.

[buffumjr]

I'll do that. I found a website where they promise to rebuild the board for $120.
http://gemelectronics.ieasysite.com/
I have an email in to them to see if this is still a good price.

(Big Grin) The only thing that could make your impressive tool list perfect would be a large Kearney and Trecker horizontal mill.

[buffumjr]

OK. I pulled the board. It has the designation 164431.. SUP1 and SUP2 are blown badly. Unable to read any bands. Look like 1/2W resistor. What is the ohm rating so I can replace these? Really counting on you guys.


The repair shops stay mum, hoping to rake in the Benjamins. I can't count on reading it as the resistors' cases are ruptured, and there's carbon residue.




One fellow posted a cuircuit diagram, but it had no ohm or wattage rating, only a number, like R24. Wasn't really helpful.




ANY help appreciated.

[buffumjr]

Inside the two white circles are SUP1 and SUP2. Unfortunately, the photo is too blurry to read the bands. I do get a silver band, but that's all I can make out.

[buffumjr]

SUP1 and SUP2 may be "suppressors". What might a suppressor be? Surge suppressor?

[duaneb55]

Yes, they are surge suppressors and you need to determine why they blew before just replacing them and touching off the machine or you'll be replacing them again. These protect the control circuit for the main transformer electronic shunt coil that controls weld output current.

[buffumjr]

So, maybe I should send the board to Gem Electronics. I remember watching some techs at a TV station rebuild boards. They had documents that told what voltages should be at what points, and the identity and values of all parts. It then became a matter of probing and applying current from a power source. I don't have any of that.

The main coils are ok, as the stick side works fine.

Am I in over my head?

[duaneb55]

That's puzzling as weld output is controlled by the current applied to the T1 shunt coil by control board PC1. High shunt coil current = low weld output current and low shunt coil current = high weld output current. Low/no shunt coil current from PC1 would explain why you're experiencing uncontrolled maximum weld output current when attempting to TIG.

Seeing as TIG and stick output are both controlled by T1 shunt coil current and surge suppressors SUP1 and SUP2 are both blown indicating a problem on one end or the other, it's a little puzzling that TIG mode output is uncontrollable and stick is - or appears to be.


Did you see my PM request for an email address?

[buffumjr]

Got your email. Thanks for the PDF of the user manual. I went to the troubleshooting section.

I came to a decision. I'm chickening out. Give me the white feather. I'm sending the board to Gem Electronics. They seem to be reasonable. After Gem, I'm taking the machine to an authorized Miller repair facility. If they aren't too unreasonable, I'll have them check it out before and after installing the rebuilt board. It'll cost some bucks, but without parts information, if I find a bad part, I can't replace it. Period. I'm sure if the information was somehow exposed to the public, I would have found it, or found someone who found it by now.

In repairing technical stuff, information is everything. Ignorance generates blue smoke and fires.

[buffumjr]

Great news! Disregard previous post! I called Miller Tech Support. They identified SUP1 and SUP2 as transient suppressors, part number 164412. $3 apiece. I'm going to give it a try. Still going to test the thyristor.

[buffumjr]

I dismounted and tested the SCR. Current flows in both directions, without stimulating the sensor leg. Bad. The SCR could not be ordered from Miller, but lots of places stock it. On order by mail. The suppressors arrived from Miller. They are directional. I called Miller tech support, but they had a day off. Must wait until Monday to find out how to install them.

Another Econotig came up for sale on Craigslist. Twice the price I paid. All functional. This way is more fun. Buy broken and fix.

[buffumjr]

In checking everything, I found the foot pedal was bad. Tech support said to check resistance between pins C and E. Some small resistance, 5 ohms, at full up, then nothing when off full up. Tonight, I'll pull it apart and check to see if there is a replaceable rheostat.

The suppressors were not directional, according to Tech Support. All installed, and everything back together.

Once the foot pedal issue is solved, I'll be off to the official repair facility to have them check everything.

[buffumjr]

I opened the foot pedal. It was like a legend out of computer lore. The foot pedal was filled with mud dauber nest. After working the rheostat to shake off the mud, it came to life. Now, on to the Miller repair facility.