WIA D speed control not working

[Bodgit]

I have not posted in a while. My 1956 WIA D Monarch has no speed control. Runs at 300rpm in back gear and no response with the speed pot knob up or down. Any advice?
Thanks
Steve

 

[old_dave]

I'm afraid can't help you with your speed control problem but welcome back. I remember you from some years ago. Good to see you are still around.

David

 

[daryl bane]

If it is an original WIAD, there could be a thousand reasons. But I would first check the speed control pot/pots (Clarostat). It's a double piggyback unit, and if either one of the pots goes bad (wire breaks? ) , you're sunk. And they maybe impossible to find now.

 

[Bodgit]

Ok I will do that next and report back
Steve

 

[rke[pler]

Something to look at is/are the tubes when the lathe is running. Look at the big and small thryratron pairs and make sure that they look to be about equal brightness.

 

[daryl bane]

Something to look at is/are the tubes when the lathe is running. Look at the big and small thryratron pairs and make sure that they look to be about equal brightness.

This, and just a loose connection on one of the tubes can cause perplexing problems, ask me how I know.

 

[Bodgit]

Very strange. I ran the speed pot back and forth a few times power off. Opened all covers. All looked fine. Fired it up and it ran fine. It now has a range 200-1000 in back gear.
Tubes seem equal brightness. Voltage is even at 440v potential between legs.
Not sure why this happened. Won't go down to very low rpm's.
Steve

 

[daryl bane]

It would stand to reason not doing anything other than twisting your speed pot a few times, you cleaned the connections in the pot and now they work..sort of.

 

[Bodgit]

That's my guess as well. I had not used it much lately.
Steve