my MIG gonna die?

hi group. hoping to elicit some preventative medicine. have a 3ph 300V mig welder (weldtronic -

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that i bought 2nd hand about a year ago and its been running like a champ fulltime ever since i've had it.

a few days ago its started emitting a highpitched squeel. well, lets say 'buzz' ... sortof like those old buicks when you leave the doors open.

it still works fine, but since its never made this sound before, i'm starting to get nervous.

based on that limited info, anyone take a stab at what it might be? i've heard capacitors make this sound before, and i'm afraid it might kick out on me. i'd like to take some action before i'm stranded.

no more warantee.. and there aren't any service shops anywhere around (i live in the middle of nowhere and would have to drive 3 hours to get it inspected.. since i'm in europe, that means i can kiss it goodbye for a good 2 weeks easy).

thanks,

-tony

Reply to
tony
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Has it got a cooling fan in it? Could be the fan bearings.

Reply to
mb

Take as many covers off it as you can, turn it on and get a length of rubber hose you can put up to your ear. Use the hose end to find out exactly where the squeal is coming from and start checking those parts out.

Good luck-

Paul T.

Reply to
Paul T.

mb, yep its got a big fan in it. the buzzing sound continues even after the fan has gone off.

the sound (buss) is consistent. when the fan is running its hard to pick out. when the mig powersdown, and the fan goes off, the buzzing is prevalent.

-tony

mb wrote:

Reply to
tony

I have a mechanic's stethoscope, and that helps identify the source of lots of sounds. Plus, I can play "The Mad Doctor" when I have the 24" probe in my hand, and the things in my ear and ask someone, "So, how you feeling?"

Rubber hose or mechanic's stethoscope should help you zero in on it.

Steve

Reply to
SteveB

Just a thought...

I don't know how big the caps are in a welder. In a guitar amplifier, if one sticks a metal mechanics stethoscope around in the workings, one runs a chance of killing one's self.

I'd verify that the caps are safe or discharge them before poking around with a metal thing attached to my head. OTOH, if the caps in these things aren't a danger, never mind...

Peter

Reply to
Peter Grey

I trust this is an inverter machine? If so, inverters run at high frequencies and components such as coils can move in response to the pulsing current that sets up a magnetic field. This movement causes the air to move and you hear the sound. This can be amplified by it causing the circuit board to vibrate and also components may resonate at that particular frequency making the noise even louder. So it can be nothing other than a component has loosened up a bit and is now vibrating a bit more.

I have a 2HP woodlathe that has an electronic variable frequency drive whose circuitry is not that different from an inverter and when the lathe is stopped but the circuit is still running you can easily hear a high-pitched hum or squeal. This is considered normal although some people find it annoying.

If you do go poking around inside please be careful since the input voltage on this machine can kill you and inverters often internally use very high voltages to make energy storage more efficient. Do not put anything metal anywhere near the components.

Billh

Reply to
billh

thanks for the info guys... i opened'er up today. no capacitors inside. i dont think its an inverter billh. it had a VERY large transformer on the bottom rack.

the top rack (the case is divide in two on the inside.. and it has a detachable top.. with the wire on it)

anyway the top rack has two large voltage setting rotary switches and a small transformer (about the size of a grapefruit) the hum/buzz was coming from the small transformer.

sounded real tinny when i opened up the mig welder. like a rattling loose nameplate if you know what i mean. but nothing was visibly loose.

is this a sign of a die'n transformer? should transformes make buzzing sounds (again, its never done it before)? is this all very normal?

-t>

Reply to
tony

Tony, I have come across lots of transformers that buzz and they keep doing it forever. The laminations are not tight and are vibrating due to the magnetic field. See if you can tighten any screws that hold the transformer together and/or hold it to its mount. Make sure that there is not something else vibrating caused by the transformer vibration.

I don't necessarily recommend it but I have heard of people loosening the screws and taking a thin knife and prying the core's laminations apart a little to let varnish run between them. Then after it dries re-tighten the screws. This probably would only be practical with transformers that have fairly coarse (thick) laminations. Some have very thin laminations and this would be very difficult to do. Personally, I would just leave it alone.

Billh

Reply to
billh

bill, thanks for the quick response. i'll have a closer look tomorrow.

i only had side access to the transformer and didnt note if it had any screws. if it helps any, the 'outter core' looked like the laminations (striations?) were welded. i mean, it was definitely welded.. i noted the pretty bead. :)

the 'inner core' was wrapped with yellow tape.

sorry for the poor terminology. i'll take the face off and see if there aren't any screws.

thanks again

-t> Tony,

Reply to
tony

Tony, The 'inner core' as you call it is probably the copper windings. Since the laminations are welded there is little you can do other than tighten any screws you find and ensure the transformer is secured to its mounting surface. There is a chance the windings are moving slightly causing a vibration. If so you can gently, and I emphasize gently, put a thin wood shim between them and the laminations and see if it will help. I would probably push gently on them and other places with a wooden stick to see if I could localize the problem. Very good chance you are going to have to just live with it.

Billh

Reply to
billh

Hum - how about the arc points ? Finally burnt down a bit and now the voltage (jump high voltage to start an arc (assume there is one)) is not arcing in time and the arc is back in the transformer / circuit.

See if there are arc points - I suspect you would have known if you had the top off - I bet they are burnt back. A little every time one used it.

Is the circuit board area somewhat clean ? maybe there is a short due to conductive dust.

Couple of ideas for you to check out.

Martin [ With TIG ]

Reply to
Martin H. Eastburn

Ah, Martin, it is a MIG.

Gary

Reply to
Gary Coffman

Sounds like one or more diodes in your welder has gone out. Have you noticed a change in weld quality and or your need to up the voltage or wire speed than normal.

Consult this diagram :

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In order to check the diodes you'll need to remove the wires, so mark them well to get them back onto the right places.

Good luck

Jim Vrzal Holiday,Fl.

snipped-for-privacy@f>hi group.

Reply to
dotdotdot

can't thank you guys enough for the tips.. haven't had a chance to open the welder up as its been working hard all week.. however..

dotdotodot & others: i'm not sure if i'm imagining this, but the welder does seem to be having a problem. didn't make much of it until i found another guy fiddling with the rollers (traction).

wire seems to be burning back much too fast / too often. typical symptom of slipping drive/traction rollers... bump up the speed, and its still not keeping up with the heat. wire is burning back and sticking.

i reset (tightened) the rollers and it seemed *ok* then i found someone doing the same thing a few hours later.

could this be voltage/transformer/electronics related?

or are my rollers just worn?

sorry, realize that might be hypothetical still, i'll know more when i open everything up. dot-dot's post got me thinking.

night,

-t> Sounds like one or more diodes in your welder has gone out. Have you noticed a

Reply to
tony

Gary - don't know MIG - thought it would have a HV unit to start the arc on it as well. Guess not.

Can an arc be struck - e.g. melt some metal ? or is there an in-line fuse-wire that went safety on you - ?

Martin

Reply to
Martin H. Eastburn

Now that I corrected my name in the newsreader I'll continue:

If you dropped a diode in the rectifier block (assuming it is a block) you'll get a large ripple in the voltage output to your gun. The more diodes you loose the worse it gets.

With one or two diodes gone (also depending where and how) will cause your transformer to either feedback (a shorted diode) or drop a phase to the rectifier block (open diode). Where I work a shorted diode usually causes the noise you mentioned.

Your welder may be using the final voltage out of the gun (via a sense wire) as a speed control to the wire feed rollers. Dropping a phase on the rectifier block will add ripple to the output and or lower the voltage which will confuse the wire feed control.

Hope that will lead you to a solution

Jim Vrzal Holiday,Fl.

t>can't thank you guys enough for the tips.. haven't had a chance to open >the welder

get

Reply to
mawdeeb

Tony, Now that another problem has come to light it very well could be related. If the small transformer is being excessively loaded due to the other problem then it could cause a hum because of the higher currents caused by excessive load from say an overloaded feed motor (assuming the small transformer powers it) or a failed component such as a diode in the circuit fed by the small transformer. Billh

Reply to
billh

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