Looking for diodes for montgomery ward welder

[Samshine]

I am hoping someone can help me.
I have a 100% dudy cycle ac/dc 250 amp. Montgogomery ward powr-kraft welder. The ac side of the welder works great. I had two repair men look at it, and they both told me the dc diodes are bad. These diodes are 5/16 inch stud type diodes, hex size is 1-1/16 1nch, overall lenght is 5- 1/4 inchs. I don't have a manual for this welder, also the numbers are worn off completely (NO WRITING ON DIODES). I do not know the open circuitt on the ac side.
I am hoping someone can tell me what size diodes i need to fix this welder.
Thanks for all the help you give me.
Samshine

 

[DennisMI]

A 100 percent duty cycle is definitely worth fixing. I understand that Century made the Powr Kraft welders, and I also understand that lincolnelectric.com bought Century. It would be worth emailing Lincoln Electric and asking. You might be able to match it up somewhere, too. I would start with Radiio Shack.

 

[tommu56]

are there 2 diodes on on 2 different plates?

double check the stud dimensions.

what is the open circuit voltage of the ac side.

I can check tomorrow at work for the brand we use on the drives.

tom

 

[oldmech]

Hi! On diodes they are part number take or the best remove one or two You can have two models for + polarity and - polarity Go at a good Welder repair shop they have in stock Expensive as $30 each Good luck! Oldmech

 

[Treemonkey1000]

If there is a manufacturer name or part number just google them. There should be lot's of electronic parts supply places online. Diodes are pretty common just the current and voltage characteristics are what you should compare.

 

[Steve Bosshard]

Most Radio / TV and Industrial Electronic places use or sell NTE brand general purpose rectifiers. This link may be useful.

Industrial Rectifier Selector Guide

Would be good to talk to the OEM folks and see what they recommend. Also some public safety equipment used BIG diodes on their gosh awful big alternators. Forward current and peak inverse voltage are the main figures of merit. Also some may have the cathode to the case and others the anode to the case. Kinda like the red and green print on diodes when alternators first were used on automobiles.

Best success, Steve Bosshard

 

[Samshine]

Thanks everbody for thier imput.
Thanks steve for the web side. I lookked in the industriial rectifier guide you sent me. If i was going to puy of size i would get the NTE6154. Its the same size as the one came off the welder, except this one has a 3/8 stud and mine is a 5/16 stud. All i know is i need a pos. and neg. diode. Which one is pos.? and which one is neg.? Also not sure about what anade to case and cathode to case style is? Thanks for all your help. Hoping to hear from you soon.
samshine

 

[Treemonkey1000]

Don't go by the stud size. You need to know the voltage and current spec's for your original diodes. Then replace with the same or possibly higher spec's. The diodes should go in the same way as the defective ones which will rectify your voltage to DC. There will be a arrow symbol on them with a horizontal bar across the tip of the arrow. That end should be the cathode end.

 

[Steve C]

I am hoping someone can help me.
I have a 100% dudy cycle ac/dc 250 amp. Montgogomery ward powr-kraft welder. The ac side of the welder works great. I had two repair men look at it, and they both told me the dc diodes are bad. These diodes are 5/16 inch stud type diodes, hex size is 1-1/16 1nch, overall lenght is 5- 1/4 inchs. I don't have a manual for this welder, also the numbers are worn off completely (NO WRITING ON DIODES). I do not know the open circuitt on the ac side.
I am hoping someone can tell me what size diodes i need to fix this welder.
Thanks for all the help you give me.
Samshine

I probably have the same welder. Mine is in great shape and all the numbers are there, model number and serial number. Unfortunately it is 200 miles away at the moment. It is a 250 amp ac/dc machine but it only has a 100% duty cycle up to about 100-110 amps. It has a slide type heat control on the front of the machine that you move up and down and set it with a locking lever to change the amp setting. The duty cycle is printed on the side of the amp scale.

I have a similar Wards 295 amp AC welder here at the farm. It is very similar in looks to the ac/dc machine but on the AC/DC it also has a set of electrode plug ins aranged horizontally at the bottom of the machine.

They are both 30+ years old and work very well.

This is a picture of my wards AC machine. If you look at the amp scale next to the slide control you can see a line at the 130/140 range. Everything above that line is 100% duty cycle, everything below that range is something less. For my use it is indeed a 100% duty cycle welder because I don't use any rods that require me to go beyond those ranges but at 250 amps on my AC/DC and 295 amps on my AC machines they are not 100% duty cycle welders. But they sure would be worth fixing if they needed it. They weld very good.

The next time I am near my Ac/DC machine I will try to get you the information you need, if you haven't found it by then.

 

[CCWKen]

Anode to case means the bolt mount is Positive.
Cathode to case means the bolt mount is Negative.

You'll need, at least, one of each for 30-cycle (half-wave) DC.

On diodes, the Cathode or Negative side is marked with a band or bar. Some of these (the type you need) may have only a diode symbol printed on the case. It will have a solid arrow pointing at a bar.

"--->|---" or "---|<---"

The bar side will be Negative. So on one diode the negative will be the pigtail and the other the case (bolt mount) will be negative.