Reviving another free mower: Black and Decker corded LM110 (rectifier)
 

These things seem to find me like stray kitties:

http://ecorenovator.org/forum/attach...1&d=1435171427

This is an AC (corded) Black and Decker LM110 lawnmower that a neighbour rolled out to the curb a couple of weeks ago.

"What's wrong with it?"

"I dunno. It quit working half way through cutting the lawn."

They're ridiculously un-complicated. Even not knowing what was wrong, there are only a few possible culprits:

- switch (most likely culprit)
- wiring
- motor brushes
- rectifier/diode
- ??

Also, I already have one exactly like it, so I couldn't resist. It's light and has been dead reliable (except the metal where the wheels join the body is weak).

Specs:

http://ecorenovator.org/forum/attach...1&d=1435171427

Model: LM110 04/80 (probably date of manufacture)
Type: 2
7 Amps

Made right here in my small city, before the B&D plant closed down.

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First I took apart the handle/switch to test for current with a multimeter. The switch was fine; juice was getting through.

Next I took off the motor cover, and AHA! Here's our problem (bottom):

http://ecorenovator.org/forum/attach...1&d=1435171427

These are bridge rectifiers that convert AC electricity into DC that the motor needs. Top: replacement; Bottom: looks like something blew and the terminal burned up.

http://ecorenovator.org/forum/attach...1&d=1435171427

Rectifier part number (MP254 / V408) led me to eBay where I bought the silver replacement -- KBPC-2510 Bridge Rectifier 25A 1000V.

$1.88, shipped. Delivery from China took a couple of weeks.

Here it is installed:

http://ecorenovator.org/forum/attach...1&d=1435171427

I put everything back together, plugged it in ... and it whirred back to life! Another mower saved from the crusher!

Hopefully this new rectifier lasts 35 years like the first one.

It gets warm to the touch after just a few minutes -- I haven't cut the entire grass yet, but I have sharpened the blades and will try it out. Will report back!

Nice and you cant beat the price.

Nice find... and nice save! I laughed when I heard the repair cost. That is awesome.

Are you going to keep it, give it away or sell it?

It's a keeper!

I'm going to see if my dad wants it. He's got a much newer corded mower but it's quite a bit heavier than this. He might appreciate the lighter weight.

If he doesn't want it, it'll become my stunt double back-up mower and will hang inside the garage on the wall until needed.

I am surprised that you replaced the failed part with an identical part, and not a part with twice the power rating of the failed part.

-AC

Actually, I did! (Higher rating.) Through no foresight on my own, though. It was one of the first available ones I saw and the price was right, so I got it.

Chance was your friend!

-AC

Interesting they used a DC motor and rectifier rather than a common induction motor.

Must have been cheaper to make?

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The mower got its first big workout in damp & longer-than-usual grass, and it's A-OK.

The rectifier (FYI, it's 25A 1000V rated) does get warm -- I'd guess 100 F. But I have no idea if that's normal or not - I've never checked the temp of its twin mower. .

Induction motors cant put out the torque needed for such an application and still be small and light weight.

I used one of those from 2006 to 2011 when I lived in Virginia.
Last year I picked one of for use here, it was broke and free. Just like you said there wasn't much that could be wrong with it. Turned out the switch was bad, I think a new switch was $14 with shipping.