Hi, I have a miller gas powered welder that was made in the middle 70's. The rheostat is bad, the parts description says it is a ww 50 watt 25 ohm. I figure that the ww is wire wound. cannot locate a new rheostat with 25 ohms, the new rheostats i have come across are either higher or lower than 25 ohms. Will a new rheostat that is 50 watt 30 ohms work in it's place? Thanks.

 

A 50W 30Ω unit will have a slightly lower current rating that a 25Ω unit. Not sure how critical that is in your application. Can you fit a larger unit, say a 75W, 30Ω one. That would likely work and give you some margin.

 

A 50W 30Ω unit will have a slightly lower current rating that a 25Ω unit. Not sure how critical that is in your application. Can you fit a larger unit, say a 75W, 30Ω one. That would likely work and give you some margin.

Thanks for your reply. I will check out the 75w, 30 for size. there is also a 50 watt 20Ω ohm rheostat listed along side the 50w,30 what one do you think would work the best?

 

This is only a guess, but the rheostat probably controls the field current for the DC generator. Since the range of a rheostat is usually 0 to max, a lower ohm value simply wouldn't have the range of control whereas a higher ohmic value would have higher range. If my guess is right, the 30 ohm 50 watt unit would work, especially if your usage is intermittent duty. Any chance of you getting schematics of your welder?

 

Try Miller part# 030987 Go to www.miller4less. they have it for 119.76

 

This is only a guess, but the rheostat probably controls the field current for the DC generator. Since the range of a rheostat is usually 0 to max, a lower ohm value simply wouldn't have the range of control whereas a higher ohmic value would have higher range. If my guess is right, the 30 ohm 50 watt unit would work, especially if your usage is intermittent duty. Any chance of you getting schematics of your welder?

The Miller site has almost all of their schematics online. But you need the serial number of the model. Or at least you used to.

 

Try Miller part# 030987 Go to www.miller4less. they have it for 119.76

Thanks for the web site it. I am going to order one from them.

 

Gald I could help. Check out Weldingweb , there are a lot of knowledgeable folks on welder repair.