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Hello all,

I was resawing some spruce today when I heard a loud bang come from the motor area of my bandsaw, as I went to investigate this is what I found, does anyone know what part of the motor this is? Any idea what caused it? As you can see it blew a hole in the plastic housing and the part inside was smoking. By the way this is a Minimax MM16 with the 4.8hp motor.






Thanks,
Greg

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Gwaltney Guitars

Hmmm. Looks like it blew a piston. Unusual for a 2 piston model...

Sorry, I couldn't resist

Looks like the capacitor blew.

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Aoibeann

Hey Greg,

Lillian is right, those are your start and run capacitors. Hopefully Bruce Dickey will chime in and he may be able to tell you what happened but in any regard you need to change them. I would contact Mini-Max, and see if they would like to keep you happy. Don't those saws have Baldor motors?

Shane

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Canada

I wish they did have baldor motors, instead they an Italian brand. Yeah, I already had to replace the switch just beyond the warranty and the Minimax people were not very helpful, so I don't expect much comfort from them here either. Other than the few problems I've had the saw is awesome.

GG

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Gwaltney Guitars

This does look like a blown capacitor. They are not brand specific and should have the value written on the side. Any good electric motor shop should have one and if that is not the only bad part they should be able to fix it. I would replace the cap and give it a try.

I'd replace both of them, in case the other one was damaged in the explosion.

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Aoibeann

You can tell if the motors still ok by spinning it over by hand then turning on the electric very crude but effective. If it doesn't run then check the continuity of the start and run windings and eny faults to earth. Friends had a similar problem where there was a long run of cable to their workshop creating a large volt drop so when we lowered our voltage from 240 to 220 so we could import some from France the start winding had to wark harder capacitor went was replaced, then eventually the starter winding burnt out. You may be able to pick some clues from that.

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Formerly JJH

I learn more from my mistakes than my successes

All electrical items have smoke in them. If you ever let the smoke out, they will not work...

Yep....capacitor

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Brad Tucker

Reminds me of my dear old grandmother's belief: If you leave a light socket empty, the electricity leaks out and you waste your money.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

I had the same problem with my switch...I guess I shouldn't feel bad since I got the same "not so helpful" service. I love the saw...just wish the service was better.

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Brad
Avon, OH

Speaking as someone who worked as a service tech for many years (pro audio industry though) its very rare for a large cap to explode with that much power.

i would never recomend this but we used to wire caps accross the mains to see which ones would explode with he most force.
we found the smaller caps blew up with most force and larger bang.
most large caps usualy just dome up on the top with a disapointing hisss or at most leak but i have never seen a large cap explode like that even with 240 vac across it.
sometime we would wire caps up to a variac and see how much juice they could take over the speced voltage (strickly for research reasons) and most caps took alot of current before they blew.

i am not sure if is still the case with motor caps but i would have thought the cap would fail long before it ever exploded with that much force to breack the plastic casing as well.

It is diferent with motor caps becouse you can put alot of strain the motor caps when resawing so it could well have caused this damage but i would not think it normal.

Any chance of opening the casing s we can see the component in question just out of interest,

joel.

Wow! How cool is that? Big bang, no real damage. Could have been much worse. Make sure when you replace the capacitors that the resistors are good too... perhaps they are integral to the capacitor, but something let that cap get overcharged.

Mike

No big deal, same thing happened to my pool pump a couple months ago. Capacitor died is all. Take the old one out (or the whole motor) to a rewinding specialist and they should be able to put in a new one for $20 - $40.

Just curious, what actually happens when a cap fails? Pressure? From what? (my background is ME, not EE, though I do understand energy density (pressure analog).

Mike

Shane you should have read more closely.

Greg was resawing spruce.

That makes it likely that his saw is allergic to spruce, blowing the cap.

I liked whoever suggested checking line voltage, that's a simple check.

My specialty is residential and light commercial wiring. Not too many 4.8 HP saws running on 220 at most homes. Grin....

I can't for the life of me think that spruce with a sharp blade would need anywhere near 5 HP to cut it. My saw is only 2 HP/ 220V.

Capacitors are cheap, buy an extra, save a trip. Good luck finding the cause, hopefully the cap is all you need. Let us know, we can all learn from your dilemna.

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http://www.dickeyguitars.com

Yeah, I'm running the saw on 220, It's never even bogged down before, I was having a bit of a time with the spruce as it was a bit damp and really I could have been using a better/different blade, but still I was surprised when she blew. I've used this blade before for resawing spruce with no issue, though I think it is time for a re-sharpening trip.

Greg

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Gwaltney Guitars

Here are some pics of the capacitors, I'm hoping someone can help me decipher what to order from the info on the capacitors...I'm really lost with this kind of stuff.

This is the one that exploded



And this is the other one, I noticed that it was a bit discolored around the connectors, like plenty of heat had ocurred, should I replace this one too?



Thanks for your help.
Greg

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Gwaltney Guitars

It looks like the top one says 60 micro-farads with a rating of 450v - these are the important numbers for ordering though you could probably go with a slightly lower voltage rating (assuming you're not running 450vac that is) but it's not a bad idea to have some safety factor.

The lower one says 160 uF which is quite a bit bigger. My AC motor class was like 15 years ago and I can't remember at all even how the starter cap works. I can't remember if the size really maters for a starter cap i.e. if you need at least 60 uF will putting in a 160 harm anything?

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

very bizare that that cap went so bizaro on you.

its very rare for a large to pop like that they usualy just dome on the top.
but it may becouse it had a hard plastic casing usualy they are made of a softer plastic that is designed to leak rather burst.

but yes the first one 60 micro farad 450 volts ac and the is 160 250 volts ac.

make sure you buy a starter cap and any old cap wont work you have to buy a starter cap or else you saw wont start .

Joel.

Joel, what is a starter cap? which capacitor is it for?

Thanks,
Greg

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Gwaltney Guitars

Greg,
The start capacitor is part of an additional relay - (the start winding). It allows the motor to produce more torque so that the motor windings won't draw too much current. This what that centrifugal switch is for just behind the motor fan. Once the motor gets up to a certain speed the switch disconnects the start relay. You should be able to start your machine even without a start capacitor. There is no harm done once it is running but the starting process will be much harder on the motor. I would give a quick call to Minimax and ask them what they recommend for the starting capacitor - sometimes these companies will discover that something else works better. More than likely there is nothing wrong with your saw - sometimes start capacitors just blow.