Ongoing quest for a monarch-motor brush/tach question

cpd62

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I just looked at another Monarch 10ee. Was in decent shape except for an awful paint job and pretty grimy ways and taper attachment. The guy had not cleaned it for 10 years.

He had fitted a solid state DC drive to control the motor and left all controls intact. My one issue was that the rpms's wouldn't go past 2100. It's a 1944 round dial with a typical max of 2500. Everything else seemed to be working well. He flip flopped on why it didn't hit max rpm. First he said the oil needed to warm up, then he said the tach is old and "it's a 70 year old machine, what do you expect?". He said he changed the motor brushes about 5 yrs. ago.

I'm trying to figure out what could be the cause of the rpm issue. It seems like a functional machine and I probably wouldn't be limited by that. But could this be a sign of bad things under the hood. The guy is an EE (and made sure to inform me that he has a PhD). Seems like he knew the ins and outs of the machine. Wish I could say he knew the same amount about paint and cleanliness.

Your thoughts and wisdom are always appreciated.

PS: He'll deliver it for $3100.
 
Good One!

If he changed the motor and control scheme, what else did he change?

Maybe the old belts and pulleys did not fit so he grabbed something close.

Who knows?

Without being able to see and check the DC drive output it is hard to troubleshoot.

Got any hints?

Love this stuff.
 
The belts and motor all look good.

I've gotten a bit more info. The DC solid state drive is an Allen Bradley (he'll be sending a picture tuesday). He did not install a "boost transformer". I've spoken to Cal Haines about this and he says that without this the max armature voltage will not be optimized. I'm thinking this may be the answer. But am putting these clues together based on a synthesis of other folks expertise.

ANy thoughts are welcome. I have also posted a similar question on the electrical forum and will see if anyone there has input.

C
 
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