Dead switch, or motor...

[Dokkodo]

Ive been given a ferm belt/disc sander, fairly hefty and well made thing so that was nice. however, its not working. The switch buzzes in the off position, but clicks on ok and tests with a voltage pen and multimeter indicate current getting through to the motor, the capacitor seeeems ok according to the test i found online.

whacked the motor case apart and stuck the voltage pen in, it lit up, so seems powers getting in there. No buzz or anything, total silence, no attempt at spinning at all on the motors part.

Is the motor likely dead? ive ordered a replacement switch, in case, but seems theres power getting through, its just noisy in off.

cheers!

 

[sunnybob]

No switch should buzz in the off position.

Assuming its an NVR switch, make special note of the connections. Its possible they have been reversed. Live and neutral in, two wires to the motor out. I have had 2 brand new machines with the NVR wired backwards, one of them was a belt/disc sander.
Assuming the switch is wired properly and then you get live to the motor, its most likely to be the capacitor. Only a micro farad tester will give you the exact capacity, its not good enough to say "it seems ok" If the capacitor is only producing half of what its supposed to, the thing will hum.Also, have you actually checked that the thing turns freely by hand? A jammed mechanism will cause a hum.

 

[Dokkodo]

Cheers bob -

will play with the connections, though if a motor is wired backwards does it not just run backwards? excuse my laymans understanding...

... which may also mean my rudimentary testing of the capacitor wasnt conclusive. However, no hum from the motor or capacitor, all completely silent. Makes me think maybe theres a connection been lost at that end?

Maybe ill order a new capacitor anyway and cross my fingers...

 

[novocaine]

pull the brushes and replace. clean the stator/contactor with IP. unless there is obvious signs of someone messing with the switch, leave it be.
replace the Cap as already said (they are fairly cheap) you can bypass it if you want to see if the motor turns but shouldn't run it like this as it'll backfeed and can cause issues elsewhere.

the motor is AC. if it's wired backwards it will stall as it will be out of phase.

my money is on the brushes.

 

[Eric The Viking]

though if a motor is wired backwards does it not just run backwards? excuse my laymans understanding...

That is NOT understanding at all. This is an AC circuit at mains voltage and you are quite wrong in your assumption.

Be very careful: you are dealing with potentially lethal electrical parts. I strongly recommend either reading up on AC and motor theory (via t'internet - Wikipedia or similar being a good place to start), and/or finding someone nearby who does understand and can look at the unit for you.

It doesn't sound like it's completely failed, but probing a live machine with a neon pen is a BAD idea. Never mind the obvious danger of electrocution, are you ready for it to suddenly burst into life?

For what it's worth, your description does sound like a switch problem - it might even not be faulty, (just wrongly wired, as Sunnybob suggests), but ignorance and electricity make killer companions.

Please, please take care.

E.

PS: Before doing anything else, make sure this thing has a proper earth, as it has a metal case. If it only has two wires in the mains cable, you need to be extremely careful (I would change that arrangement for three, but then I know how to do that safely). Do all your testing with it plugged into the mains via an RCD (the 13A plug-in type will do). That way, you have a slightly better chance of not killing yourself if you make the chassis live by mistake.

PPS: I know what Novocaine means, but it's internal to the motor. On the machine/switch, live and neutral might be swapped without changing the motor rotation. The difference is that one way round is far safer than t'other.

 

[sunnybob]

No, I very clearly stated that the SWITCH could be wired backwards IF its an NVR switch.

I had exactly that hum from the switch on the axminster drill press I bought. It worked, but it made a noise it should not make.Rewiring the switch connections cured the problem and it has worked perfectly ever since.

I had a belt /sander brand new that started as soon the wall socket was turned on, and the machine would only stop for as long as you held the start button in. Reversing the connections also cured this machines problem.

If the motor is free running by hand and the SWITCH connections are correct, its 99% likely that its the capacitor. [/u][/u]

 

[Eric The Viking]

Wot 'Eee said ^ ^ ^

 

[novocaine]

and assuming it was working for your mate and there is no sign that the switch has been messed with I still reckon it's the brushes.
or

I am ignoring the noisy in off though, so I'll grant bob a cookie for his comment . I think FERM use magnetic switches not a mechanical NVR. the buzzing in off is most likely because the magnet contacts are ****** internally. so it won't show signs of tampering as it hasn't been wired backwards really, it's failed internally.

or its the capacitor. guessing at electrical faults on line is like trying to keep your wife happy, without it in front of you, you are always going to be wrong.

 

[sunnybob]

How do you manage that? My wife is only happy when she's NOT in my immediate vicinity. :roll: =D>
And I did say if it was an NVR, twice! 8)

 

[Dokkodo]

Thanks for your advice chaps, sorry i realise I sounded cavalier, do have some experience with electronics, enough to know how not to hurt myself at least.

Will try these suggestions and hopefully will get it running in time for some Christmas present knife making projects. Thanks!

 

[Dokkodo]

Sorry to drag this back up but ive now embarked on some Xmas projects which would be great aided by having this running if i can...

So ive replaced the switch, was magnetic and as you guessed it was just junked up and buzzy.

And i got a new capacitor and tried that, silence...

which leaves me with

I still reckon it's the brushes.

but ive had the motor open and apart and dont really know what im looking at, ive replaced brushes before in RO sanders and a drill but i dont see anything of the sort in there or anywhere they might go...

just to recap, voltage pen indicates power all the way through to the motor, but then nothing, no buzzing, no moving.

had it suggested i get a new motor but for the cost of that i could just get a whole new one

any final advice before i scrap the poor thing? seems a shame, its just what i need.

 

[sunnybob]

Do you have an ohm meter? if power is going into the motor but not coming out, and assuming the motor turns freely by hand, there is a break in the windings that can only be confirmed with an ohm meter.
If the windings are broken, I suspect a replacement motor will be 90% of the price of a new unit.

 

[Dokkodo]

thanks bob,

i do have a meter yes, so i check for continuity through the motor and if there isnt any its kaput? windings cant be repaired then...