Find some one with small fingers. This is mostly a mechanical job. Remove capacitor with wrench, and/or screwdriver. Assemble new capacitor and properly solder new ring connectors to same length of old. Install capacitor with same tools.

 

Maybe the old capacitor was rated at 500v because the welder can be wired to run on 480v?

Yes, it is clearly marked on the front of the machine right under the big Polarity Switch, "Do not switch under load"

As i say, these internal wiring problems are above my pay grade, so I'm the Middle guy here, but here is a quote from a welding forum regarding this capacitor..maybe it has merit in our discussion here?...

"Capacitors can pass AC but block DC. I think one side of that cap is connected to ground? If that is what it does it is likely there to shunt AC generated in your DC arc to ground to protect something upstream in your machine. I haven't studied the diagrams but that may be what it is for and for $0.47 if it blows again buy 2. It may have simply shorted from old age and then burned off because it would then be trying to carry the welding current to ground."

Well, i ordered 5 of those little suckers from Post #10, thanks a bunch - you guys rock!!

 

You might want to look at those switch contacts while you have it open. I believe the purpose of the cap is to protect the contacts from pitting. The contacts will tell you if apparatus has been abused. Anyhow, it looks like it did its job well.

 

$3.23 at www.mouser.com

http://www.mouser.com/ProductDetail/Vishay-Sprague/565CZ5UBA102EX503Z/?qs=sGAEpiMZZMtGtrSL1omHbPKjoR6sJy7tSFIG9xCIP1s=
Not exactly the same, but it will probably work in that position.

A 0.05 across those massive bus bars is not in a critical position for frequency or accuracy.

Not unless its a HF aluminium welder.

 

Yes...it has HF, that can be switched on and adjusted - to weld Aluminum. It is one of it's claims to fame.

 

C13

 

Hey guys, this is a TIG welder that has a "high frequency start" feature. This means that the welding arc is started by inducing a high frequency high voltage between the workpiece and the electrode. This starting voltage is UGLY. It is basically an industrial cattle prod but cattle prods are built with more elegant electronics. The older TIG machines used a gas spark gap to produce the "high frequency"starting voltage.

What am I trying to say? That cap lives in a very harsh environment. Miller chose that kind cap for a reason. It should be replaced with the same kind of cap. Going to a 1000 volt cap as #12 suggested is a good thing, just so long as it is in the same family of ceramic capacitors.

 

For Frame of Reference - Right in the center of this pic, the bottom right hand small switch says "high frequency"... And the huge black plastic lever on the lower right is actually the Polarity Switch in question throughout this thread...





And down on the lower section, there is this knob to adjust the intensity of the High Frequency...so, yes - there IS High Frequency involved in this machine at times. Did i order the wrong capacitors, I ordered the exact one in post #10?? (O - to the far right...the square Aluminum arrangement...those are the High Frequency Spark Gaps also)

 

Tbert
I can not tell from the data/numbers on the Jameco website if this is the right capacitor. The capacitor you need is hard to find now days. The cap that #12 suggested in a non-stock item.

I have found some others:

http://www.ebay.com/itm/05-mfd-500V...793?pt=LH_DefaultDomain_0&hash=item462761be11

http://www.ebay.com/itm/05uf-500v-d...325?pt=LH_DefaultDomain_0&hash=item1e92ba721d

I looked for 1000volt caps, no luck

 

Post #12 merely says "C14" ... What is that?

 

Look at the schematic of your welder. Each symbol has a reference designator which is normally a letter and a number, in this case C14. The C means a capacitor and the 14 means it is the 14th one in the schematic. We are looking at the pictures you posted and the schematic and trying to determine which capacitor is which on the schematic.

 

Oh, ok - So, the ones I ordered from post #10 are not the correct ones? I'm confused ( but that doesn't take much).

Also - I took many random pics initially, so let me know if any more are needed. I buttoned up the welder and rolled it under the bench to await the capacitor's arrival, but it is easily-accessible for anything specific. Thanks, this is a tremendous help!!

 

The capacitor from Jameco I posted is Z5V rated one so it should work.

 

OK I see it now. The cap you ordered is a Z5U. (I had to go to the catalog page.) It should work fine. Sorry for any confusion.

 

Hey guys, this is a TIG welder that has a "high frequency start" feature. This means that the welding arc is started by inducing a high frequency high voltage between the workpiece and the electrode. This starting voltage is UGLY. It is basically an industrial cattle prod but cattle prods are built with more elegant electronics. The older TIG machines used a gas spark gap to produce the "high frequency"starting voltage.

What am I trying to say? That cap lives in a very harsh environment. Miller chose that kind cap for a reason. It should be replaced with the same kind of cap. Going to a 1000 volt cap as #12 suggested is a good thing, just so long as it is in the same family of ceramic capacitors.

Not only that - but there are several different types of ceramic used in disc capacitors. Most ceramic capacitors have more lossy dielectric than the best of film capacitors. There are specialised film capacitors for the high voltage/high frequency/high energy pulses in TV flyback tuning circuits - the manufacturer probably didn't use one of those because disc ceramic were a *LOT* cheaper.

Years ago I worked for a company that made high power ultrasonic cleaning and plastic welding plant - they *NEVER* used disc ceramic capacitors for anything.

 

56nF at 400 volts and "high" frequency actually transmits a lot of energy- might be part of the problem.

some replied said it was well chosen but i dont think so, probably just on the margin.

I've seen the latter too many times to believe in well-selected components.
I've seen a GE 2W fluoro nightlight just exploding after a few weeks.

One brand I really like is Panasonic- these parts are still like new after two Decades.

 

56nF at 400 volts and "high" frequency actually transmits a lot of energy- might be part of the problem.

some replied said it was well chosen but i dont think so, probably just on the margin.

I've seen the latter too many times to believe in well-selected components.
I've seen a GE 2W fluoro nightlight just exploding after a few weeks.

View attachment 73843

In my TV/monitor servicing days; I saw a lot less disc ceramic flyback tuning capacitors than the special foil types, but the disc ceramic types accounted for about as many failures as the foil types.

 

I appreciate all the feedback, this is so over-the-top... way more than I expected. I'm just waiting on the capacitor order to come in, at this point. Jameco says arrival date should be Friday. I don't feel like it would have hurt anything to weld w/ it the way it was?...but why take the chance. thanks so much guys!!

 

Here is what i found, is it normal for all that plastic to blow out the back?



Or do you think it was some type of insulator that i shouldn't have pulled off that busbar? Oops.

Does it matter that they arent the same physical size???

 

Or do you think it was some type of insulator that i shouldn't have pulled off that busbar?

I believe you are correct. Probably meant to keep the capacitor off the contacts. They may also be using it to maintain clearance requirements.