Jet JWBS-16 Bandsaw - electrical issues

[kmcleod]

All,

I have a Jet JWBS-16 bandsaw, I live in uk, so its single phase.

Up to now its been fine, but over the weekend, it died on me !

Press the start button and it trips out the electrics in the workshop, not just the circuit its on, but all the electrics...so one minute power and light, the next, no power and no lights.

Step 1 - replaced the 13A fuse in the plug - same result

Step 2 - , make sure there isnt anything else causing the trip - so I and either swithched off or unplugged everything, else, and killed the lights - so the only thing connected was the bandsaw - hit the switch, and click, the trip goes out - so its definately somehting in the saw.

Step 3 - opened up the power connection - no smell of burning - so nothing obviously burnt out.

Have check the mamual - not a lot of help, basically says to do the above,,,

Any ideas / suggestions ?

Thoughts are that there is a ground somewhere, either a wire, or a dead capacitor ot the like

Thanks

Kevin

 

[Ttrees]

Hello you've checked that everything is free from obstruction
i.e wheels turn freely, without a blade and/or belt removed.
no noise from motor like something stuck in the fan.
Does the same thing happen without load,
This might tell you something.
Myfordman has a lot of tricks to find out things if it's motor related,
i.e caps or centrifugal switch.

Since powers tripping, it doesn't sound like dust trapped inside the NVR or whatever switch/button you have.

The next thing might be to check the capacitor for damage,
this would be what I'd be looking at first.
Whip off the cover on the box on top of the motor.
There could be a slight bulge or some sort of burning.
Should be under a fiver for replacement (the same physical size if needed to fit into the terminal box) and obviously the same rating.
Ill leave that to someone more knowledgeable to answer

Can these hold a big charge for some time after being unplugged?

Aswell as that, try and find out if the motor has a centrifugal switch.
These can get a slight bit of corrosion and need a wee bit of cleaning
(I think there's stuff you can apply for the job)

 

[Myfordman]

Which trip is being affected? sounds like the RCD if it is killing the lights too.
If its the RCD then you are looking for earth leakage paths, trapped wires biting though the insulation or worst of all a cooked motor.
Tracking down needs a cold logical approach and expertise that can't really be transmitted through forums.
Sounds like you need a local expert enthusiast capable of analysis rather than a "replace everything until the problem goes away" approach that most sparks will take.

 

[danst96]

Have you had a look at the capacitor?

 

[kmcleod]

thanks for the feedback guys.

After replacing the fuze in the plug I opened everything up and make sure of was all clean - no dust etc, and that all of the wheels rotated easily, (they did), so no obvious instructions.

I did take the cover of and check the large capacitiy on top of the motor - no bulges etc, though I was a bit wary of it given these things have the ability to give you a healthy jolt if not treated with respect.

Suspect ifs going to be a case of stripping the entire thing down and working through it step by step...

 

[mindthatwhatouch]

What sort of switch is on the machine, check for damage to the cabling, have you eliminated the socket that its plugged into?

 

[kmcleod]

yes, elimated the socket, that came after fuze etc. By switch what do you mean - the machine has a power switch on the from, which connects to a switch box on the rear, then to the motor / capacitor, its also got an electrical brake

 

[Ttrees]

Did you ever notice a click every time the machine was switched on or off?
That would be a centrifugal switch, inside the motor.
Some motors have them, some don't.

There are some ways of testing your capacitor, or indeed capacitors if theres two of them,start and run, but I'm not familiar with them.
With no load from the belt, does it trip, does it start at all? backwards?

Have you tried anything else to test the supply,
depending on the motor size that could be quite a demand for a brief second.

 

[Gordon Tarling]

From what you've told us here, it's tripping from an earth fault rather than an overload. Please ask a professional to check it out properly, as that earth and RCD are all that's stopping you from receiving a shock at the moment - definitely not worth messing about with if you don't have professional knowledge and training.

G.

 

[kmcleod]

So no click on the motor, so i dont think its a centrifugal switch - though have asked Jet customer service to confirm.

As t comments about the earth and RCD - I take on board the concern etc, but as I've wired my house, and been doing electrics for longer than i care to mention I've got a healthy regard for safety, especially around electrics, so feel fairly comfortable doing fault checking etc - plus the one professional I already spoke to said - oh the easy answer is to replace the whole lot, new switch gear motor etc - which isnt really the aim of the excercise.

 

[Inspector]

I would bypass the switch and wire the motor direct and try and turn it on with the breaker. If it runs your switch is the problem. If it doesn't and trips the breaker you have a motor problem and are down to trouble shooting and fixing it.

If bypassing the switch spooks you disconnect the motor and hook a different one up to the switch. If the breaker trips it is the switch and if it turns on the motor the one on your bandsaw is the problem.

Pete

 

[Distinterior]

I had similar symptoms to you on my Axminster White 450 floor standing bandsaw last year......I thought the NVR switch was faulty as it kept tripping the RCD as soon as it was pushed.....I ordered a direct replacement switch and when it arrived I took the existing switch off only to find it was full of sawdust. Once cleaned out & refitted it works fine and there was no need to fit the new switch..... Result!

 

[kmcleod]

cheers folks - there will no be a slight delay while I take this thing apart !!

 

[Spectric]

Did it "die" whilst in use or when you next came to use it? As MyFord man said you need a logical approach rather than take it totaly apart and that means you need to isolate the fault. So disconnect the motor from the on/off switch and try again, this would tell you if it is in the switch unit or downstream. If the motor belt is removed then it should spin freely and then if it still trips you need to get the motor checked which unless you have the equipment is a case of taking it somewhere. Another potential could be mice, they like chewing wires.

 

[AJB Temple]

I have this saw I think. Certainly a 16" Jet. Sometimes it is a bit erratic starting after a period of no use. Can you hear it trying to start? I have found that holding the back of the blade and pulling it down in the direction of rotation can start the saw. I never have to do this if the saw is in regular use. It's worse with a big blade highly tensioned.

 

[Myfordman]

So no click on the motor, so i dont think its a centrifugal switch - though have asked Jet customer service to confirm.

As t comments about the earth and RCD - I take on board the concern etc, but as I've wired my house, and been doing electrics for longer than i care to mention I've got a healthy regard for safety, especially around electrics, so feel fairly comfortable doing fault checking etc - plus the one professional I already spoke to said - oh the easy answer is to replace the whole lot, new switch gear motor etc - which isnt really the aim of the excercise.

If your level of electrical knowledge is such that you think changing a fuse is a good thing to try when you have a earth leakage type fault you really ought to get someone in who knows what they are doing.

 

[Spectric]

As t comments about the earth and RCD - I take on board the concern etc, but as I've wired my house, and been doing electrics for longer than i care to mention I've got a healthy regard for safety, especially around electrics, so feel fairly comfortable doing fault checking etc - plus the one professional

Are you saying you are a professional electrician, an electrical engineer or just someone who believes they are competant? For an electrically qualified person this is a simple case of fault finding, it only requires a basic level of fault finding to isolate the issue and as for that "professional" you consulted who just says replace everything I would question their competance. Fault finding is all about taking a logical approach to understanding the type and location or component that is causing the fault. First stage is your load is a motor, now if there was a short, live to neutral then the 13 amp fuse should melt to provide electrical disconnection but it has not, instead the RCD has tripped indicating a leakage path to earth that has exceeded 30 mA. So disconnect the motor and recheck, if all is ok then start to suspect the motor, check the insulation of the windings and the fault will show itself.

 

[Nick.]

I'm 95% sure we sold these with a 16amp blue plug on..

I know at shows we could occasionally get away with swopping for 13amp 3pin as organisers 16amp supply cost a fortune, but it was hit and miss if we blew other stands electric off.

Did you buy it 2nd hand? Or if new did it come with a 3pin 13amp? - I know it's been working up until now but higher tension & wider blade is enough on start up to pull the amps easily with those heavy wheels and trip the MCB on just 3 pin - especially if the whole machine is a bit old and stiff on bearings etc.

Can you try it with the drive belt off? Just see if the motor starts with no load - that may indicate if you are drawing too many amps for 13amp when it's all fully tensioned etc..

I don't know your RCD or MCB set up but as others have said you really need to double check that aspect too in case there is earth leakage.

 

[Nick_D]

13A plug for a 1.5-2HP induction motor is pretty borderline - component age might have affected the motor load to a point where it's tipped it over the edge. If you bought second hand the previous owner may have switched the plug.
Does it take a second or two to trip, or is it immediate?

 

[Gordon Tarling]

Just a reminder that the OP stated that the saw is NOT tripping the MCB, but the main RCD, which indicates an earth fault rather than any form of overload.

G.