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View Full Version : Toasted my TIG machine - help? :(



Tony
05-25-2012, 05:12 PM
Decided to fix a problem I didn't really have.. and now I'm out a nice
150amp AC/DC tig welder. Man I feel like crap.

Homebrew foot controller worked fine.. didn't have the full range (couldn't
get down to below 10amps and couldn't get past 140 or so).. because
of the way the potentiometer mech in the foot pedal worked. (cosine error :) )

Anyway, bored one day, decided to finally "fix" it.

And boy did I.

Made a new pedal (all metal this time, no plastic crap) and was "tuning in
the range" of the pot with the pedal on my bench -- the same bench
I had the torch/ground rigged to along with the ammeter!

ps.. here's a vid of the pedal.. turned out pretty nice I think.

Sh*t -- and I thought $300 for the OEM pedal was highway robbery.

http://www.youtube.com/watch?v=nzKuQQKcclM


So long story short I think I had a short in the on/off switch in the pedal
(to the metal casework) and I think I sent HF/HV up into the machine.

Now here's the crazy part.. I've been told HF/HV back to the machine
causes MAJOR damage.. but the whole machine works just fine except
for one little small thing: I can't get any more than 5 amps out of the
box!

Arc strikes and is stable.
Up slope / down slope works fine.
I can selected AC / DC / Stick / Pulse / Freq, everything.. but the amp
control on the box is gone.

Called the mfg (Cemont).. they told me it was a bad control board.. $250.
ORdered it, waited 2 weeks, put it in.. nothing has changed.

Called them back: "Well we have no idea where HF/HV might go send us the
machine but probably needs a new mobo" which is something like $600 + labor.

Machine is (WAS) worth $2k. I don't have the money to throw into it.. its a hobby
I don't know how I even managed to buy it the first time.

So I'm going to dig in myself.

Anyone out there into electronics and know anything about inverter style welders?
Looking for tips / things to look for / etc.

First I got to figure out how to safely discharge these large caps with the sticker that
reads: Discharge me or die!


Tigless Tony

lazlo
05-25-2012, 05:22 PM
Made a new pedal (all metal this time, no plastic crap)
here's a vid of the pedal.. turned out pretty nice I think.

http://www.youtube.com/watch?v=nzKuQQKcclM

I can't help you on the control board, but wow -- that's a very nice foot pedal mechanism!

John Stevenson
05-25-2012, 05:30 PM
Tony,
Try here.

http://www.mig-welding.co.uk/forum/index.php

Brit forum but some very clever people on there.

914Wilhelm
05-25-2012, 05:35 PM
I often discharge caps that are low voltage (less than 440v) by using a light bulb placed in a temporary pigtail socket. Just touch one wire to each side of the capacitor. The lightbulb will light briefly and fade out as the cap discharges. If the bulb blows (excess voltage) use two in series. It sounds like your machine is putting out the minimum amps and I would suspect whatever got fried was what was first in line where the pedal plugs into the machine. Look at the portion of the circuit first. Look for burn marks from diodes, ICs and resistors. Have you checked the machines output with your foot control out of the circuit and deselected on the machine? Maybe you cooked the foot pedals potentiometer causing the machine to default to lowest output.

MrFluffy
05-26-2012, 03:20 AM
I have exactly this problem on my tig, but its a old relay based sinewave set from the dawn of time.
I lost power from the amps control in all modes and it just gave base output selected on the range selector, first I checked out the contactor which throws in when you trigger the tig torch , bad contact and a clean up did that good, then found a relay burnt and not switching the contacter in.
Ive now got full power control back on MMA because the selector switch for the machine bypasses the latching trigger/pedal circuit which I think still is damaged, but still no tig. But I came in with sore eyes after tracing wirewrap loom for 3 hrs.
Mentioning it because I think its how tig's are architected, and even though they're completely different you have to work on the modern equivalent section of the circuit to my relays and wires...

Tony
05-26-2012, 04:42 AM
Thanks guys.
John, I'll have an ask over there too.
This is an italian machine.. and I'm here in Italy.. funny thing is the
only one who'd even talk to me was a chap named Paul at Telford group
in UK. Great guy.

We cemont told me it was the analog control board I spent a whole
day taking it apart, piece by piece and checking. Checked out fine, but
I'm not EE. I should've trusted myself.

There are two sets of wires: torch switch and pot.

They all go to the analog board first, then the logic board below it.
Nothing is burnt/blow (first thing I looked for).

Thing is, the switch leads also run elsewhere (jumpers) and go deep into
the machine.

They really pack these things tight!

I'm hoping to find something obvious when I dig in.

And I just ordered a new CK 9 and 17 with superflex cables!

Tony

aboard_epsilon
05-26-2012, 06:22 AM
nice pedal... lovely job ..that's precision ..i like it .

I'm scared to death of anything electronic ..not afraid of the shock from the electricity ..but the price to fix .

my tig has transformers ..and a big windy handle ..and Doctor Frankenstein Hi Freq - jump the gap - generators.

bullet proof ..and hopefuly "fool" being myself ..foolproof.

OH.. IT'S ITALIAN AS WEL...L CEBORA

all the best..markj

Tony
05-26-2012, 06:50 AM
yeah some of those older Cebora are bullet proof.
I've got an old plasma cutter thats been to heck and back..
probably full of 10lbs of slag and still works like a champ.

Consumable are expensive though.

Best I can tell the only "digital" part of this welder is the logic
board. And I'd imagine HF/HV spike would've blow the surface
mount stuff to kingdom come.

Rest of it is all big transistors and transformers.

If nothing else this is a good excuse to finally pick up an old
oscilloscope. :)

How do they design these things so tight? I'm surprised air
can even make it through this machine.

Tony

John Stevenson
05-26-2012, 07:51 AM
nice pedal... lovely job ..that's precision ..i like it .

I'm scared to death of anything electronic ..not afraid of the shock from the electricity ..but the price to fix .

my tig has transformers ..and a big windy handle ..and Doctor Frankenstein Hi Freq - jump the gap - generators.

bullet proof ..and hopefuly "fool" being myself ..foolproof.

OH.. IT'S ITALIAN AS WEL...L CEBORA

all the best..markj

That's the one of mine that's broken...............