Cordless Mulching Mower woes (Black and Decker CMM 875)

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Yes, Bob, the blade spins very freely.

They happen to be easy to locate and inspect and they look intact and in good contact with the armature, but I'm not a motorman, so I am not exactly sure what to look for other than good contact and not even sure how to determine that precisely. Based solely on the small amount of use the mower has seen over the years, I tend to believe the problem lies elsewhere.
I can hook a multimeter up to the brush contacts and look for high resistance reading - I'll Google "motor brush inspection" to see if I can find out more about the brushes. My gut feeling, from the way it performed (well) up until the moment of its death, that the brushes are not the culprit. I would expect that mode of failure to be gradual and noticeable in performance/function <g> degradation. This was five seconds of spin and then nada, zip, zilch, nothing.

First thing. Even swapped in a known-good battery of similar voltage. I would never have expected a sealed lead-acid battery to last 16 years, but apparently it did. The original (looks to be a 40Ah job - can't see the label without dismounting it, though) is roughly 12" on all three sides. That's why the next step is to bypass the controller board (containing a relay and a voltage regulator) and to power the motor directly from a known good battery. Since one of my theories is that something got wet, I am waiting until the unit has been indoors under humidity control to dry out. Also thinking of squirting it with WD40 to displace any moisture still trapped.
If I could get to the solder side on the controller board, I would trace the power to the relay. The whining sound it makes when trying to engage doesn't come from the motor, it comes from the controller board, and when I find my stethescope, I will try to determine precisely what is whining. I suspect it's the relay. Removing it isn't going to be easy but may be the only option if no replacement parts are available.
Thanks for your input!
-- Bobby G.
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The name B&D goes along with cheap power hand tools, thats a name I avoid.
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They also own DEWALT, I guess B&D is low endof market Dewalt the pricier one
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wrote:

They also own DEWALT, I guess B&D is low endof market Dewalt the pricier one ========================================== http://support.blackanddecker.com/app/answers/detail/a_id/4104
Implies they own Porter/Cable, too.
-- Bobby G.
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