Black & Decker MM575 electric lawn mower

lacchuji · 05-31-2009, 12:19 PM

ran over power cord and sliced it in half

. circuit tripped. got new cord. checked that blade was spinning ok when turned manually. i think shaft is ok and did not get damaged. but the mower motor does not turn.

what could be the problem and how do i fix it? grass is growing like crazy and i need help quick.

thanks.

**octaneman** · 05-31-2009, 08:55 PM

Hi lacchuji

There 2 types of electrical motors, AC driven and DC driven. You have to find out which of the 2 you got. AC motors have brushes and thermal fuses in the field windings that propel the armature. In DC motors its magnets that act as the field core, In DC motors there is an external diode bridge ( It's a square metal box in the middle with a bolt going through the center of it on some models) that connects the switch to the armature. The bridge changes AC to DC to allow the motor to work. If the motor is AC you need to replace the thermal fuse. If its DC you need to replace the bridge.

**Basementgeek** · 05-31-2009, 09:07 PM

Hi and welcome to the forum

While you have a mower problem, it is not a small engine problem, it is an electrical problem.

Going to guess you live a newer house and the outside outlets are protect by both circuit breakers and GFI (Ground Fault Interrupters). Cutting the cord probably tripped both. Some house used a GFI Breaker, in the breaker box and some used GFI outlets.

Make sure the outlet you are trying to use has power.

BG

05-31-2009, 12:19 PM	#1 (permalink)
lacchuji Registered User Join Date: May 2009 Posts: 1 OS: macintosh	Black & Decker MM575 electric lawn mower ran over power cord and sliced it in half. circuit tripped. got new cord. checked that blade was spinning ok when turned manually. i think shaft is ok and did not get damaged. but the mower motor does not turn. what could be the problem and how do i fix it? grass is growing like crazy and i need help quick. thanks.

05-31-2009, 08:55 PM	#2 (permalink)
octaneman Mentor Home Support, Gearhead Automotive Center Join Date: May 2009 Posts: 543 OS: WINXP	Re: Black & Decker MM575 electric lawn mower Hi lacchuji There 2 types of electrical motors, AC driven and DC driven. You have to find out which of the 2 you got. AC motors have brushes and thermal fuses in the field windings that propel the armature. In DC motors its magnets that act as the field core, In DC motors there is an external diode bridge ( It's a square metal box in the middle with a bolt going through the center of it on some models) that connects the switch to the armature. The bridge changes AC to DC to allow the motor to work. If the motor is AC you need to replace the thermal fuse. If its DC you need to replace the bridge. Last edited by octaneman; 05-31-2009 at 09:00 PM.

05-31-2009, 09:07 PM	#3 (permalink)
Basementgeek Moderator, Home Support Join Date: Feb 2005 Location: Central Ohio, USA Posts: 1,474 OS: XP Pro SP2/Vista Ultimate SP2 Blog Entries: 3	Re: Black & Decker MM575 electric lawn mower Hi and welcome to the forum While you have a mower problem, it is not a small engine problem, it is an electrical problem. Going to guess you live a newer house and the outside outlets are protect by both circuit breakers and GFI (Ground Fault Interrupters). Cutting the cord probably tripped both. Some house used a GFI Breaker, in the breaker box and some used GFI outlets. Make sure the outlet you are trying to use has power. BG __________________ Donating to the forum keeps TSF free for all. Proud member of ASAP Last edited by Basementgeek; 05-31-2009 at 09:10 PM.