# Century "five Star" 295ac/250dc Welder



## amuller (Feb 11, 2016)

I just picked up one of these for $25 and have been going through it.  I checked all the diodes, got the shunt and its operating linkage working smoothly, it seemed ready to go.  But the fan motor failed the first time I tried to weld with it.  (It was working when I buttoned up the machine.) The motor coil seems to be open and these little motors aren't cheap.

So, are these welders any good?  Worth the investment in a new fan motor?  Or should I write it off?

I also notice that while the welder is rated 295 A, the instructions inside the cover don't seem to recommend rod above 5/32.  Is this really a 295A welder?

Thanks for any guidance.


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## RJSakowski (Feb 11, 2016)

Small fans abound.  Assuming the welder is otherwise working, I would just find another fan and swap it out. You should be able to test the function of the welder without needing the fan by making a few short welds. 

Based on my Miller welders, there is not a problem with space inside the case.  I would think that some of the old 120 vac axial fans which were used on the earlier computer power supplies could serve well.  They come with different cfm ratings so look for a higher rated one.  Otherwise, fans from old dehumidifiers put out a good air flow.


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## brino (Feb 12, 2016)

Does it have configurable input voltage?
Could you have accidentally put 240V on a 120V fan? 
(I only speculate as you don't say how deep your clean-up/checking has been, if you replaced the line cord/plug, etc.)

I have found some welding machines overly generous with their faceplate/marketing current specs.
I do not know this machine specifically, but the best thing to do is try it with larger rods/jobs and find the limit yourself.

However, be cautious of the "duty cycle" rating........you may find you can only weld at higher currents for one or two minutes out of ten!

-brino


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## amuller (Feb 12, 2016)

brino said:


> Does it have configurable input voltage?
> 
> Yes, but 208/240.
> 
> ...


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## amuller (Feb 12, 2016)

RJSakowski said:


> Small fans abound.  Assuming the welder is otherwise working, I would just find another fan and swap it out. You should be able to test the function of the welder without needing the fan by making a few short welds.
> 
> Yes.
> 
> Based on my Miller welders, there is not a problem with space inside the case.  I would think that some of the old 120 vac axial fans which were used on the earlier computer power supplies could serve well.  They come with different cfm ratings so look for a higher rated one.  Otherwise, fans from old dehumidifiers put out a good air flow.



The design of this one doesn't lend itself to easy access or a different size fan.  I'll have to remove the diodes/heat sinks to get the fan out.

The dehumidifier fan idea is good and I happen to have a couple of dead ones in the rathole.  Except that they will be 12o volt fans.  Could be connected between a hot leg and the ground but that would not be good practice.

Thanks for the good suggstions.

Alan


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## LucknowKen (Feb 12, 2016)

When the fan on my Powermate 220 Amp mig died the cheapest replacement was over $100 US plus shipping.
The fan motor was 240V. I bought a crate of 220V space heaters that all had good fan motors.
I was shocked to find that the fan motors ($20 for the crate) were a direct fit.
The crate was marked "vestibule heaters".


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## RJSakowski (Feb 12, 2016)

How about an external fan if you can't get one in the box?  A 120 volt fan should be OK.   Many pieces of equipment pull off one leg for 120.  Bottom line, that's whats done anyway, just at your load center.  You have an issue if you lose your ground connection but if you do, there are bigger concerns.


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## amuller (Feb 12, 2016)

LucknowKen said:


> When the fan on my Powermate 220 Amp mig died the cheapest replacement was over $100 US plus shipping.
> The fan motor was 240V. I bought a crate of 220V space heaters that all had good fan motors.
> I was shocked to find that the fan motors ($20 for the crate) were a direct fit.
> The crate was marked "vestibule heaters".



These welder fan motors seem to be readily available but cost $80 bucks or so.  It's a very simple shaded pole motor and it could be the easiest thing to just rewind it, if in fact the coil it really burnt.


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## chips&more (Feb 12, 2016)

Check the fan coil for damage. Does it have that fried smell? Could be just a loose wire/open connection. Does the coil have good color? Then check where the magnet wire/winding wire transitions to a terminal or it might transition to another kind of wire. You can always rewind the coil. I noticed the type of welder you have on the net. The fan motor has a simple one field coil. Easy enough to rewind…Good Luck, Dave.


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## amuller (Feb 12, 2016)

chips&more said:


> Check the fan coil for damage. Does it have that fried smell? Could be just a loose wire/open connection. Does the coil have good color? Then check where the magnet wire/winding wire transitions to a terminal or it might transition to another kind of wire. You can always rewind the coil. I noticed the type of welder you have on the net. The fan motor has a simple one field coil. Easy enough to rewind…Good Luck, Dave.



Just my own line of thought!  The fan is attached to the rectifier assembly and I won't be able to inspect the coil until I take it out, but as far as can tell the coil does not seem burnt, and I don't know why it would be--the bearings are free and it was running fine, and it's *cold* here in Minnesota.  So hoping it is a lead connection problem.  In any case, the secondaries of the transformer and the choke are aluminum, and the terminations rather rudimentary, so taking them loose for a cleanup and treatment with joint compound is likely enough a good idea.

Thanks again.

Alan


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## chips&more (Feb 12, 2016)

amuller said:


> Just my own line of thought!  The fan is attached to the rectifier assembly and I won't be able to inspect the coil until I take it out, but as far as can tell the coil does not seem burnt, and I don't know why it would be--the bearings are free and it was running fine, and it's *cold* here in Minnesota.  So hoping it is a lead connection problem.  In any case, the secondaries of the transformer and the choke are aluminum, and the terminations rather rudimentary, so taking them loose for a cleanup and treatment with joint compound is likely enough a good idea.
> 
> Thanks again.
> 
> Alan


Well, if it is that cold. It could have a thermal fan switch. And it’s just off because it’s so cold?


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## amuller (Aug 7, 2020)

Well, I see I started this thread SIX years ago and just got back to working on the machine.  And here is the thread just waiting....

Found fan with a 115 volt motor wired across the line, so no too surprising it burned out.  So I cleaned up connections, checked the rectifier diodes, hung a fan on the outside, and it worked nicely for about five minutes before one of the rectifier diodes shorted.  Disconnected the DC side and it works ok as an AC machine.  So it uses 150 A 300 volt stud mounted diodes and these are a bit expensive.  Cheapest I've found so far is $19 and most vendors are around $40.  I'm not sure it makes sense to replace just the one.  On the other hand, a complete 200 amp bridge rectifier in one piece is about $20 and a 300 amp is $30-40.  Does anybody know if the rating of the one-piece bridge is equivalent to one individual diode, or do I need to apply a factor?  And, what sort of spike protection should I put on the new diodes or new bridge.  I guess this is more of an electronics question but people here usually know stuff.


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## markba633csi (Aug 9, 2020)

Hi Alan, I would replace just the one diode.  Motorola and International Rectifier are good brands.  I'm not sure I trust the import bridge rectifiers I have seen.  Something USA made I would trust. Besides it's more work, doing a conversion.
As far as spike protection, you could add a snubbing capacitor across each diode, something like 0.22 uF (microfarad) at 400 volts mylar type certainly wouldn't hurt.
-Mark
BTW, the airflow is very important to make those diodes live.  Make sure any replacement fan has good strong flow, especially if the diodes are mounted on a smallish heatsink and there are cables and such that interfere with the airflow path, and you want to do high duty cycle dc operation


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## Cooter Brown (Aug 9, 2020)

Just zip-tie a Big box fan to the side of it and wire it in.......lol

Just like my friends refrigerator.........lol


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