Old 180 SD HF stuck on

[lunatic]

High i just bought a used syncrowave 180sd and im new to tig welding. What is the symptoms of the hf being bad?

[Tweekster]

it either works or it doesn't.

Push the pedal, get a HF spark, then the arc starts, and the HF spark stops the arc continues.

You can tell by the way it sounds.

[chromenuts]

Same Problem?

I wasn't sure if I should post here and dig this old thread back up, but this is really the only lead I have found which seems to describe the problem I am having with my Miller 180SD. I was hoping to get some feedback and find out if the OP was able to fix his machine.

I bought my machine used a few years back from a professional welder for some projects I had. He gave me the box and a regulator along with a cheap torch and ground clamp for about $800. I had to invest a bit more to get it set up the way I wanted it, including a foot pedal, tank, new ends for the torch and ground clamp, built a cart, lcd helmet etc. In the end probably closer to $1200. I used it a couple times and it worked fine on stainless and aluminum, then it sat for over a year and a half.

When I started it up again the other day to weld up a small piece it struck an arc and welded fine the first time, but when I paused to move the piece I started hearing a constant buzzing noise from the machine. I wasn't used to it and didn't know what to make of it at first. I turned the machine on and off, tried all the different modes, but it happened in every one as soon as I power it up. I took the cover off and saw that there was a constant spark across the gaps. I also noticed the torch would now arc across to the work constantly. It would still weld if I hit the pedal, but the arcing wouldn't stop.

I cursed a lot and scratched my head. I had a look at a manual I had downloaded and tried adjusting the spark gap and blowing things off with low pressure air. Wishful thinking I suppose.

So yeah here I am looking for help. The new boards I have found are about $750 online. I did call around to the welding supply that was helping me with some of the parts when I first got the welder and they were nice enough in turn to refer me to the welder repair service they use, who in turn was nice enough to tell me about a company they sometimes use called Innovat Corporation which will rebuild the boards in this model for $237. A little more poking around and I found Gem Electronics out of Florida that will do a "Quick Fix" of 2-3 components for $190. That is all much better than $750, but I am currently out of work and only getting small side jobs here and there for money.

My electronics knowledge is limited. I have also tried to troubleshoot some audio equipment of mine in the past with help from other people in DIY forums. I have a basic multimeter, soldering iron and etc. I was hoping that if the problem had been tracked down to the chip located at U8 that I might be able to find a replacement and fix this myself. I realize I would have to confirm that my board has the same problem, and would need guidance with that.

For now here is some other information and pics. The serial number on my unit is LA114611. Stock #903600.

Here is a pic of what is happening with the arcing at the torch with the unit powered up but the pedal still not activated. (I have tried disconnecting the pedal and all other cables to see if that makes a difference, it doesn't)

http://i97.photobucket.com/albums/l210/chromenuts/IMG_20110818_135437.jpg

And of the spark gap at all times after power up

http://i97.photobucket.com/albums/l210/chromenuts/IMG_20110818_134954.jpg

A pic of the main board assembly number 190772

http://i97.photobucket.com/albums/l210/chromenuts/IMG_20110826_172013.jpg

closeup of U8 on main board

http://i97.photobucket.com/albums/l2...826_174805.jpg

I have other closeup shots of the main and daughter board etc., but I think this post is a bit extensive already. I was able to easily locate the HCF4098 chips on ebay should I need them. Any feedback will be greatly appreciated.

Regards
Kevin

[ccawgc]

please carefully reread this complete thread.
Now, does the HF stay on in all modes including stick and AC and DC TIG.
At power up, no remote control plugged in?
If yes the opto triac may be shorted. The HF would turn off in stick for the OP so on his pcb the opto triac was good and the control U8 turned out to be bad.
No short cuts here. you need to do all the tests. learn about the parts you are testing or get help. Or send it off for repair.

[cruizer]

So, put a switch in before the hf transformer coil on the primary side to save some coin, turn it manually on and off when needed. If I couldn't say repair a board cost effectively there is no point for the customer to invest more money in an older machine

[chromenuts]

Testing

Hi ccawgc,

Thanks for your comments.

does the HF stay on in all modes including stick and AC and DC TIG.
At power up, no remote control plugged in?

Yes the HF does stay on in all modes...with and without the pedal plugged in to the machine. I also tried disconnecting the torch and ground cables. No matter what I try the HF starts on power up.

I reread the thread as you suggested. This stuff is a bit above my head. The schematic in the manual I downloaded and on the machine are the same and is hard for me to interpret. It doesn't look like it illustrates anything that I can understand as far as the opto triac and other components being mentioned and how they work in the PCB circuit. I understood enough (when I referenced cruizer's comments) to be able to locate the wiring and components related to the HF transformer and I should be able to cut power to the HF transformer at wire #4 if needed. I was considering the solutions cruizer offered, but I thought if it was possible to get the machine working as it was meant to I would prefer it.

For now, I started at the beginning and took a resistance measurement across the terminals for RC1-7 and RC1-8 on the PCB. I already had the board removed from the machine. I wasn't sure how I could take the readings with it installed and reasoned that I was testing the circuit on the board and hoped it didn't matter. I hope I didn't make the wrong assumption. My readings like this were much different from the OP's. I only got a reading with the polarity of the MM probes oriented in one direction which was with the black/negative probe on the RC1-7 terminal. I took a measurement of just short of 1300 Ohms like this. When I was adjusting the scale on my meter I noticed that I could take readings as I switched to 2k, 20k, 200k etc. but that they were different and not just shifting the decimal of the orignal measurement I took. I should say that this is an inexpensive Craftsman MM. Do I need to install the board to take the measurements properly or have the machine powered up? If not, does this give any clear indication as to the state of the Q3 opto triac that is mentioned?

I researched the number I found on the Q3 (Q2004L3 with TE9 printed on the lower segment)and wasn't able to find an exact reference to the TE9 portion. I did find this...

http://www.newark.com/jsp/displayProduct.jsp?sku=56J8537&CMP=KNC-G-SKU-LIT

I know I'm jumping the gun, as I don't even know if I tested things properly or if any conclusions can be made without more detailed testing. It was just a search to see if I could find anything as a replacement should I need to. I have no ability to determine if its specifications are appropriate.

[chromenuts]

Anyone have feedback on the board before I resign myself to trying cruizers ideas?

[cruizer]

Problem is that we know its an optocoupler or a relay on the board, If you don't have the required equipment to fix it, then you either send it out for repair, or get a new one.

Now with repairing they have generally a 60% chance of fixing it, and you are still paying even if its not fixed.

Without an expensive tracker, your simply not going to find out whether a component works or not. and if you do happen to replace a part that say was a IR component with a replacement NTE part. Often that replacemnt part isn't exact, and the unit still doesn't function the way its supposed to.