miller thunderbolt ac/dc help

[arkansawer]

I have an older miller thunderbolt ac/dc model. The welder welds fine on the AC side but nothing on the DC side. The two neg. polarity diodes didn't show a reading at all either way so I ordered both of them. I have been reading since then that I should replace all 4 (2 positive and 2 negative) diodes so everything is in synch. Is that right or will I be all right replacing just the negative polarity diodes? Thanks for your help.

 

[RCPro87]

You will be fine replacing only two. The only reason it is recommended is due to the age of the existing ones. I have just replaced one before.

 

[davo727]

I have one of those welders in my collection and I added a 5inch cooling fan that blows air into the case. I think it is a wonderful thing since that original fan just blows a little air around inside the case and relies on convection to get air in or out of the welder.