HF Start Repair Linde 185 AC/DC TIG BOC Smootharc Ryval

[tjones99]

New to the forum. Pretty new to TIG welding. I have been using a borrowed Linde 185 AC/DC TIG welder (finally bought it off the owner!!) and ever since I have been using it I have had to use lift start because the HF start was not working. I have never used HF start for TIG so I had no idea how it behaved... Today I got it working and OMG HF start is awesome...

Read many posts on this forum in the process of hunting. Time to give back in hopes it helps others.

I spent a LOT of time on the web looking for a schematic or service manual for the welder and discovered that the Linde 185 AC/DC welder was the same or VERY similar to the BOC SmoothARC or the Ryval welders so I am mentioning them in case it helps others with those. No love. Could not find.

At the same time I had the welder apart and I noticed in the area of hte spark gap that there was a power resistor that was fried and broken. Looked like a smoking gun to me. But the resistor was beyond recognition so no way to get a value from it. I needed help.

Then while searching through Google Images of welder schematics I happened on a picture from someone that had designed his own HF trigger circuit. The pictures he posted (reposting here) looked similar to my welder so I looked at his post. He posted two pictures and while different from mine it was close and the SECOND picture showed what looked like the upright resistor that was fried in mine... and the poster had also posted a schematic fragment... even before I found the schematic I noticed there was actually a silk screen on the PCB that showed 5W 1K!!! Score...



I sourced a 5W and a 10W 1K resistor and got to the repair.

Disassembly looked daunting... but I discovered that I was able to remove only the bottom panel and leave the bulk of the welder intact so I could get at the solder pads on the bottom of the PCB to replace the resistor.

Once I had the bottom off I discovered that the PCB had arced and burned near the spark gap.


I repaired that using a Dremel tool to grind away the PCB (not the traces!!!) that is burned because burned PCB is conductive and will continue to arc across. Basically I just made the air gap that they build into the board larger!

I soldered in my 1K 10W resistor in place of the 1K 5W original just because there was room. I suspect 1K 5W would have been fine.

Not sure how the original failure happened... one theory is the welder was left wit the trigger pressed for a long time maybe laying on the bench or dropped and this resulted in continuous HF arc at the spark gap and maybe moisture or dust provided a path across the PCB resulting in an arc path that once started would forever get worse.

Happy to report that HF start now works and OMG does that make fine TIG work SSSSOOOOOO much easier when you can get into proper position and just start welding rather than lift start that ends up pulling you too far away and the arc stops etc... In fact I think for crappy welders like me it helps more than it might with the pros!

Just hope this helps someone down the road!

[Jack Ryan]

Nice work - congratulations!

By the way, BOC is a Linde company.

Jack

[adamkrizsan]

Hello, my name is Adam, and i hope i can revive this thread for a little time. I have a Rotenbach WIG 200P TIG/MMA only with hf(not the large but the smaller one) which is apparently the same as Everlast or Super machines. And i have the same problem, however when i got the machine hf was forking for a year or so, but one day it started not to work but it was easy to solve by turning the machine on and off. I think it worked like two times then it never came on again(hf), but i could still lift weld.

So I looked inside the machine and i instantly spotted a burnt resistor. I couldn"t read the resistors value and i was a bit scared to remove it, because i didnt know if it could have been the problem or it was just dirty. Anyway after reading this post I rushed over to a nearby electronics store and I bought a few ceramic 5w 1k resistors, quickly replaced it and the new resistor burned instantly.

It made it obvious in my head that I have a much deeper problem and i dont know where to look at im not exactly a professional in circuits, but i did my best and couldnt see any damaged or irregular parts on any circuit boards. I can make photos, i can solder and buy parts locally so i would appreciate any help locating the error.

If somebody can hear my desperate cry into the void,


please help me