Brush/rotor issues Mixmaster Junior.

[mattl]

Well I've finally got around to reassembling my Mixmaster Junior I posted about a few months back.  It cleaned up pretty well, I'd give my efforts a B, I'll post pictures later.

 

Anyway I opted to reuse the original cord as it was in fair condition and the replacement I bought was a bit too stiff and slightly too large to easily fit into the hole in the body.  I soldered the joints and heat shrink tubed them, got the everything stuffed back into the body and decided to try out the motor before I did the final assembly.

 

Issues are it won't start on it's own, if I spin the shaft it will start, slowly on high, and it arcs continuously.  There is a full ring of arcing around the brush area.  I let it run for a minute or two hoping it just needed to clean off any stuff that got on the contacts, but no improvement.  I've never done much with motors so I'm at a bit of a loss.

 

OK, experts out there what did I do wrong?  It ran fine before.

 

[rp2813]

Might it be as simple as changing the placement of the brushes?  As in, same end of brush against the armature, but switching which side of the armature they were installed on.  Or are you sure they went back where they were to begin with when you reassembled it?

 

[mattl]

I didn't remove the brushes, but they might have gotten rotated 180 degrees when I reassembled.

 

[d-jones]

Matt

The phenolic plate that the brushes mount to is notched on one side so the wires going to the switch in the handle can pass by. I don't think it could be assembled 180 out. That being said, how are you able to see all of the arcing and sparking you've described? With the front bearing in place the brushes and armature are completely blocked from view, and if the plate containing that front bearing isn't installed and you're running the motor, that could be the source of the problem. The armature needs to be properly supported at both ends to work correctly. I'll apologize in advance if I'm way off base here.

 

[mattl]

I've run it both ways, with and without the bearing plate. There are gaps around the plate and I can see a lot of arcing. With or without the motor won't start on its own, got to help it.

 

[d-jones]

Just to be sure we're talking about the same thing, this is the front bearing plate. There is a bit of a gap at the base of the handle but otherwise it should fit very snugly all the way around. I did a cord replacement on one of these a while back and posted the process here on the blog, so have a look at the thread and see if anything strikes you as different about yours. I'd like to help more but without being able to see what you have I'm at a bit of a loss to explain what's happening.

 

By the way, there's also a link to an excellent replacement cord in that thread towards the bottom. It's made for hair clippers, but once you cut the molded end off of it and strip it back a bit to expose the wires for your connection it works great. It's the same diameter as the original.

 

Mixmaster Jr Cord Replacement

Some time ago I mentioned that I had a Sunbeam Mixmaster Jr that seemed underpowered and needed a new cord. At the time the advice I got from the board was basically to leave it alone, as reassembling the mixer after opening it up would prove very difficult. Well, the cord was so darned ugly...

www.automaticwasher.org

 

[this post was last edited: 8/27/2015-14:44]

 

[mattl]

We are talking about the same part.  With the plate on I can see lots of arcing through the area by the handle, and the motor won't start without help.  In your other pictures the commutator is much cleaner than mine, mine is sort of dark, bordering on black.  I was thinking about cleaning these points but was worried I'd cause problems.  Now I guess it does not matter.  Just have to pull things apart for the 4th time.

 

[davetranter]

Heavy arcing...

.. And won't start/run properly. I've seen this on various tool motors, usually when there are short-circuited windings in the armature. unfortunately, these small motors will overheat almost instantly if stalled. I hope that I am wrong, because it's an expensive fix :-(

All best

Dave T

 

[mattl]

I picked up some 1200 grit sandpaper today,  Will try cleaning up the contact area and see what I get.   May be looking for a parts donor if it does not work out.