Question about Welding Tools
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Posted on Jan 02, 2017
You don't say what model welder you have, some Miller welders have 3 slip rings and brushes some have just 2. In either case the next step is to use an ohm meter to check the resistance of the rotor and brush assembly. If this is a 2 slip ring model, take one of the wires off of one of the brushes then measure the resistance between the 2 brush terminals - it should be something between 10 and 100 ohms. If you get an open circuit measure the resistance from one slip ring to the other right at the slip rings - if you now get something other than an open you've got bad brushes (about $10 each to replace),
The 3 slip ring models are similar but have 2 rotor windings - take off the wire from the middle brush and measure from it to each of the ends.
If your rotor and brushes checked out OK you should next check the fuse in the exciter circuit, this will be on the block where the other end of the brush wires go.
If the fuse was good you need to do an excitation test. This is a bit dangerous so be careful. Look at the schematic pasted inside the case and figure out which brush is the positive (+) one. The wires are numbered and so is the schematic so this isn't as hard as it might seem.
Disconnect the wires from both brushes (all 4 wires in the 3 slip ring model) and tape them off so you won't get shocked. Get a 9V battery or make up jumpers that will let you connect the welder battery to the brushes. Start the welder and connect your temporary power supply, measure the AC at the outlets (it should be around 60VAC with a 9V battery) and the DC voltage at the weld terminals (should be above 10V), lastly measure the voltage at the wires you disconnected from the brushes (should be around 70V DC). Disconnect the temporary power supply and shut down the welder.
If you didn't get AC at the outlets and DC at the weld terminals above, something is wrong with the stator in your welder. If you didn't measure any DC on the wires that go to the brushes (most likely thing to happen), you've got something wrong in the exciter circuit. Check the rectifier, the capacitor, the exciter winding in the stator, and lastly the current control board. Older welders will also have the fine current control rheostat in this circuit (look for burned windings on it).
That's about all of the general advice I can give you without knowing more about which welder you have.
Posted on Dec 02, 2008
well depends did u use it in cold tempatures if so no it was u. if not then most likely or could have been just a crazzy thought here that there was a electrical discharge when it was pluged in and cracked the block on it but honestly thats 1/10000000000000 chance of happening. or it overheated and cracked it but relistically if its new then just take it back and play dumb or if its still under warrenty play dumb and get it fixed. aslo u can search for a new part on craigslist or ebay. last but not least if its not uner warrenty or new to take back or u cant find a part either thru the ones i listed or by calling the man. ur last resort is to just throw it away.
Posted on Apr 03, 2009
Switch S1 may be dirty or damaged. The field should not need flashing as that will occur when you engage the start button.
It is possible there are some faulty connections in the 24 volt control section. Loose or corroded 24 volt connections to the contactor may not be allowing adequate current to flow. The connections on the SR 1 board should be checked as well. Also check the rectifiers. THey should be moderately high in resistance with test leads held one way on the rectifier, then with leads reversed, the resistance should be at a minimum 10 times different than the first reading either greater or lesser. Use a decent DMM to test them.
Posted on Jan 07, 2012
If it is only momentary, it may be sand in the contactor- blow unit clean or as best you can and "tent" some poly plastic over the contactor with duct tape to seal it to cabinet. Use the heavier 6 mil stuff or fabrcate a cover from phenolic sheet or fishboard (flame proof material looks and feels like cereal box cardboard)- old circuit boards from derilect equipment, etc also can work, the idea is to dust proof the contactors- the heavy one especially.. Check to make sure it does not melt either as it will get exrra warm there. They were made for a metal shop not a desert. No offense intended.
Also check to make sure the circuit breakers CB1 and CB4 are sound- they can fatigue fail and/or wire connections work loose and become intermittent under load.. Also cycle the switches a few times to clear the crud. If you have LPS1 available- it can help clean the contacts and dries without residue.
Also check the trigger switch and replace it if you can find no other obvious faults with an ohm meter. If not, the microswitch might come apart to clean up the contacts. It "might" even be interchangeable with.derilect mcrowave interlock switches- which would need to be sealed with silicone out there.
If you do not have the manual for it from Miller, you can download it from their website
then just scroll down to the flavor of 302 you have. Engine controls are the only real difference between the three models
Lesser possibilities are an issue witht he current sense coil- PLG-6 attaches there- also check that connection. They would be wires 141, 142, 143, 144 They go to the main board.
Also check RC-12-1 and RC-12-3 these will be on the PC-2 board- they are the voltage sense wires and they go to switch 1.
Also check SR-1 the rectifiers- make sure they are not loose or have faulty soldering- this can drop out the voltage too.
Posted on Sep 25, 2012
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Weld Cable (+) To Feeder lead cable.
Work Cable ( - ) To Workpiece Weld cable and work cable connections to power source (DCEN/DCEP) are dependant on wire type.
Since feeder is not polarity sensitive, there is no need for an electrode polarity switch.
Voltage Sensing Clamp Connect voltage sensing clamp to
Gas Hose to regulator.
Gas Cylinder to regulator.
Use of shielding gas is dependant on wire type.
You are all set up to weld.
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