I've repaired a couple of Bosch motors for people and it has always been ei= ther a bad brush or a bad winding on the armature. The brushes are easy - they are either worn out or not. To check the armature I put another working armature in it - luckily they u= se the same motor in a lot of tools.=20 Sometimes a repair center can replace the part cheaper than you can do it y= ourself. Cris Wilson Computer Support College of AAH Clemson University 864-656-6081 -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of= KPL Sent: Thursday, April 24, 2014 8:37 AM To: PICLIST Subject: [EE] universal motor died Hi, Lots of smart people here, probably somebody can help. My woodworking router went bad, so I'm trying to find what's wrong. It's BOSCH GMF 1400 CE. There is a parts list available here: http://www.mtmc.co.uk/Spare-Parts/Bosch-Spare-Parts/Bosch-Woodworking-Tool-= Spare-Parts/Bosch-Routers/Bosch-GMF-1400-CE-/-3601F17860-Spare-Parts__p-240= -12733138-12733209-12733174-50234.aspx There is also a tiny wiring diagram in that drawing. First, I tried to skip the speed controller, by connecting power cord direc= tly to the motor, so that current went thru both field windings and a rotor= , but motor just made an ugly noise and smelled bad. Field windings were co= nnected as originally, so phasing was ok. That leaves a question - how to diagnose field windings and the rotor? Most probably it's a shorted winding somewhere, but is there a way to find = that myself, without special equipment? I have a multimeter and can try to = get my old scope out, but that's almost all that I have. I see generally that is done using some square pulses and watching ringing = with a scope. Unfortunately there is little chance armature can be rewound properly, due = to it's operation speed of 24k rpm, which would require extremely good bala= ncing. New armature costs a lot :( -- KPL -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .