I have a hobby welder that I got for free. It's not working and I have narrowed down (at least I think so) to the transformer. I am wondering how I test the transformer to see if it is pooched?

Thanks all!

Steve.

 

There are several ways to check a transformer.. What I would do is check for incoming (primary) voltage first , depending on where you are, it should be around 220 volts. If not there check power switch. If that is ok then check output of transformer, depending on welder, it should be about 25 volts..
If it's a dc output welder and you have a secondary voltage from transformer check ac input to rectifier, probably 4 large diodes with braided leads mounted on an aluminum rail.. Let us know if you need help checking diodes.
As an afterthought make sure you are supplying the correct voltage. a 480 welder won't operate on 220...

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gerty

 

The welder is 110 volt. Just so that I understand, do welders work on high voltage or high amperage? I would speculate that it's amperage and the weld is formed based on resistance causing the metal to melt. Is that correct??

 

Yes, it's high current, with fairly low voltage.

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PIC programmer software, and PIC Tutorials at:
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Since the most likely problem with the transformer would be a primary winding that overheated and burned open, I'd unplug the thing and use an ohmmeter to first check across the power cord hot and neutral prongs with the power switch in the "ON" position. You should see a pretty low resistance, say under 50 ohms. If it's open circuit (infinity on a VOM or O.L on a DMM), then check the leads that are fed to the transformer from the mains circuitry (probably go through the power switch and/or a fuse or circuit breaker) and check their resistance. Should be the 50 ohms. If so, the problem is with the wiring to the primary whether it be the power switch, fuse, circuit breaker, line cord or the wiring itself. If the infinity reading, you have an open primary. It's likely not easily repairable since the primary of and E-I core is wound on first and the secondary on top. If a double-D core, you might have a better chance, but still only if the open is on the outer layer of the primary winding.

Dean

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Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

 

Steve,

If the transformer is burned out it will show on a visual inspection. What kind of welder is it?

Ante :roll:

 

It's a Crafstman Hobby welder from Sears.

 

Sears has great repair services, Chances are you might be able to buy the broken part.
http://www3.sears.com/help.html

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Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

Steve,

A MIG? Any chance of a schematic in the manual? Any pictures? What have you tried so far, what makes you think the transformer is the problem?

Ante :roll: