Button Diodes - Rectifier - Century 117-070 Welder 90 AMP

Thread Starter

SolomonMan

Joined Jan 24, 2012
33
All,
I play around with Electronics...most for house hold repair...I do have a Masters degree in Science but not in Electrical Engineering.

This appliance is a old welder that has seen very limited use (not more than 40 hrs) since I have bought/owned it new (Close to 30 years now).

I was using it the other day extensively,(first time in a decade about 6 hours) and I left the setting knob at the highest value and turned the unit off to go to the other side of the vehicle.

Upon turning it on I heard a loud humming noise and it blew the house breaker. At this point this continued after the breaker reset so I shut it down and checked again later the next day...Upon inspection the next day I limited things down to the rectifier being shorted.

Upon inspection of the rectifier Button Diodes (12 total - 2 star patterns that house 6 button diodes each). I found a single diode that is shorted out.

So I went looking and researching replacements. I have included a schematic of the welder found on inside panel of the welder.

After doing some research (forums and welder tool parts etc) that I believe I should pick up 12 new 50 amp button diodes. The welder part stores state that the diodes are discontinued now and they were more or less universal) fits for many century welders including much larger units from what I can ascertain. I have also found a slew a 25 amp button diodes available most for alternators/battery chargers but question there size for the application.

Most promising are some AR504 Diodes (25 total pcs) on Amazon for about 40 dollars which seems reasonable but wasteful. (Only sell in 10 and 25 packs)

The questions now are mostly theoretical as recently ended up (Birthday gift) purchasing a new rectifier that is actually a Century part for the unit. I may refurbish the old rectifier...cause I do plan to use this welder extensively in the next few years on a beetle restoration/farm work.

Anyways the questions;
1) I had significant issue sourcing these button diodes...Any suggestions for a online Part store for this application?
2) I considered the possibility of a new rectifier...a non-Century Part number but what size rectifier would be proper for this unit?
3) Been told that Voltage of 400 and above in this situation is probably Good Enough. Thoughts?

Thanks everyone.
Chris
 

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Thread Starter

SolomonMan

Joined Jan 24, 2012
33
All,
Thanks for the responses!

If I was going to change/upgrade the entire Rectifier...I see a slew of them on Amazon/Ebay….What should I look for Value wise?...Not fully understanding the rectifier "sizes"...if I am a 90 amp welder...would a 100 amp rectifier be ok?

Would going to a higher amp rectifier be better?

The proper part is below (advertised as a 75 amp rectifier)
https://www.centurytool.net/860_905_666_Rectifier_p/860-905-666.htm

I guess I am curious in the rectifier there are 12 diodes....how does the amperage rate of the diode affect the rectifier amperage allowed amounts...The rectifier diodes appear to be in parallel...so the 50 amp diode universal replacements is that a 600 amp rectifier? So the universals are just taking into account much larger welders?

Universal Century Diode - Discontinued. link below;
https://www.centurytool.net/244_047_666_50_Amp_Diode_Replacement_Kit_4_p/244-047-666.htm
Thanks for all the help!
Chris
 

Thread Starter

SolomonMan

Joined Jan 24, 2012
33
All,
Again Thanks for the Responses!

On Saturday I received the new Century Rectifier!

Upon deeper inspection of the welder I found a Manufacturer date of 1995. so the unit is only 24-25 years old...

I have replaced the rectifier with the New Century Part that was verified by Century Parts...and finished my welding on my truck bed....the old farm Truck is back on the road...after a lengthy (6 month) in the garage redo...

The original Rectifier has a clearly shorted out diode...The rest (11) tested fine...but its suggested to replace all 12....My guess is the oxidation on the diodes can get thick it appears....so to avoid issue I was planning to replace all 12.

I also planned to clean the plate thoroughly and have thoroughly blown out dust/debris in and around welder on the new part install done on Saturday.

My plan was to rebuild the original rectifier to have a back up.

One thing I have noticed since replacing the rectifier...the welder seems considerably thorough..nice deep welds...and am able to quickly (not desirable) burn throw metal when set at the highest setting...when before it took much more time...So now I run mostly on the 3 setting as the welder manual suggests and get very nice welds.

Thanks for the help!
Chris
 
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