Bit of a band saw problem

[sammo]

I bought a Stratright 14/s/5 bandsaw from good old ebay - all worked fine in the chaps workshop; apart from the stop button (had to switch off at the plug) got it home, and cleaned it up; now it starts then immediately stops again. Think the switch maybe faulty (although there is a chance it's blowing the fuse - as it happens my multi-meter is also broken)
Anyone had any experience of these saws.

Chris

 

[SurreyHills]

On my Startrite 352 I had a similar issue, traced mine down to the thermal overload relay part of the DOL starter cutting in. The give away was that it reset itself after about 45seconds. Problem was ALT Spares wanted £70 for a replacement switch. So you could try a couple of things:
Bypass the thermal overload relay to test if this is the cause and if so try an find a replacement thermal overload relay of the correct amperage (my switch is a Danfoss and spares are available)
Replace the switch with an alternative, Bob (9fingers of this parish) recommended one from Toolstation (can't get the link to paste in correctly) - it's on page 271 of their catalogue. Only problem with this approach for me was that my switch is built into the column of the bandsaw and is linked to rods acting as cabinet door trip switches and the brake.

Andy

 

[beech1948]

I hadto find a replacement switch which fitted inside the column on my 352. ALT saws were pretty expensive but I was stunned to find that a google for the part number revealed the French/Belgian company who make these and purchase of said switch for £21 inc p&p.

This waS 5YRS AGO.

aLAN

 

[dickm]

Haven't got the details of the switch to hand, but could probably find them if needed. My 352 was 3 phase and after converting it to single phase, it needed a new switch (paralleling the contacts on the original 3p switch more or less worked for a while ). It's a Danfoss original, and from memory, cost only about £20 from an electrical supplier. But that was about 10 years ago...........

 

[sammo]

Thanks so far. Borrowed a multi meter so Saturday will spend time trying to find the fault.

 

[sammo]

Ok - Once you get a multi-meter you quickly discover that you are blowing fuses!

So more help needed!

Here are some internal pictures. took the covers off to make sure that there wasn't a dead bug spread across terminals ;-) (BTDT!)

When I turn it on the Danfoss unit makes a satisfying 'clunk' the bar under the Number 10 engages inwards - then the fuse blows and the bar pops out and the blade comes to a graceful halt (no brake I note!)

I have no idea what to do next - do you simply work through replacing parts until it all works ?

Normally I am pretty good at diagnostics but I am an IT bod - not an mechanical electrical engineer - so need some advice and help.


Chris

 

[deema]

If the fuse blowing is the current overload of the DOL cutting in, I think that all you need to do is increase the current setting. Looking at the picture I think it's located in the RHS (bit fuzzy). It's usually just a simple plastic lever with numbers against, increase the setting until it doesn't trip out.

 

[sammo]

Hi Deema, there are some numbers on the right hand side, in Amps 1.8 2.0 2.2 2.4 2.6 2.8 but from what I can see at the moment no obvious way to make any change.. But will look in the morning.

 

[sammo]

Well the morning revealed a clear plastic lever that was in the uppermost position (above the 1.8 number)- will it hurt to simply move it to the maximum 2.8?
Of course now I cannot find any 13amp fuses...

Chris

Ps what does DOL stand for?

 

[joethedrummer]

Well the morning revealed a clear plastic lever that was in the uppermost position (above the 1.8 number)- will it hurt to simply move it to the maximum 2.8?
Of course now I cannot find any 13amp fuses...

Chris

Ps what does DOL stand for?

D oav O ide L ectrics !!!!

 

[SurreyHills]

DOL is Direct on line just a method for starting motors.
The clunk you hear is the magnetic contactor coil in the switch being engaged, which is required for current to be supplied to the motor.

You can try and move the dial to the maximum but it may not solve the problem. The amperage for the relay seems to be quite low, mine goes to 10A. If it doesn't solve the problem you have the choices that I outlined in my earlier post.
It's either the thermal overload relay or the coil itself.

Bypass the relay to see if it is definitely this component failing, if it still fails I would think it's the coil. Both items are replaceable, rather than having to replace the complete switch. You can perform the tests by taking the switch out of the bandsaw and connecting the output to something like a hairdryer.

Andy

 

[sammo]

Thanks Andy.

moving the the lever to the max did not solve the problem.

Andy - you mention two items coil and thermal overload; are these two things contained the Danfoss relay 'block' in which case how do i go about by passing this - is it as simple as connecting the wires that go to the motor to the plug.

 

[deema]

Looking at the picture of the wiring of the switch, I think that something looks wrong. The 'switch' consists as Andy had said of a relay and overload. The mains power should come in on one end, and the power to the motor at the other end. Looking at the wiring there appears to be a power take off before the current overload. If you can sketch out what is wired to what we can have a look and see if the wiring is correct to begin with. As Stated already, the current rating of the overload device appears to be very very low. Please also have a look and list a picture of the motor rating plate so we can see if the ebay is correctly rated.

My thoughts are that this machine may have been convertered to single phase, and the DOL has not been changed for a single phase unit. If this is the case, the on off buttons may also not have sufficient current rating as well.

 

[sammo]

Ok - will do this tomorrow.
The motor isn't that accessible - I was considering taking it out and cleaning up the belt changing system.

bTW I am pretty sure this is a single phase model, I have the manual will look again at it see if there are any clues.

But that doesn't explain why it was working perfectly for years; then when I get it home it doesn't.

 

[SurreyHills]

The coil is part of the switch and to get at it you will need to take the switch out of the saw and take it apart. Leave this as a last option.

The thermal overload relay is the bottom part of the switch and is a separate component, and although it looks to be a single unit it's connected to the switch with screws. Looking at your wiring it's not right, the output wires at the bottom should go from the lowest set of screws (I.e. Fromthe thermal overload) not from the switch.

I have PM'd you with a link to another site with the correct wiring diagram (wasn't sure what the policy is about linking to other woodworking forum)

Andy

 

[sammo]

Hi - I have another NVR switch from a small bandsaw (now very dead bandsaw - it got knocked over, and didn't survive the trip!) - can I simply swap this one over? I sort of assume not, but you never know.

Chris

 

[sammo]

Latest from the shed. Disconnected the motor from the DOL - and all seemed ok, out the multi-meter on to the two terminals that the motor was connected to; and I was getting 250v output - Happy days.

Reconnected the motor, but disconnected the drive belt - guess what, motor ran without a problem; reconnected the drive belt and the fuse blows...

What next guys?

The motor plate reveals the following information
230-250 Volts
8.4 amps
1 phase
FL Speed 1450
HP 1.25
Cycles 50
Rating M/C

Brook Motor, AC Class E
Sammo

 

[sammo]

So bit more diagnostic today. Connected the motor to the thermial override as it should be, the motor doesn't even start, but at least the fuse didn't blow and the DOL remained engaged.
Going to replace the thermial override first, and see what happens next. All a little frustrating as it ran perfectly before it was moved from the workshop where I bought it.

 

[sammo]

Thanks to everyone, I now have the saw back up and running, I had so expert help from a wonderful chap called Bob, over the last week there have been a number of diagnostic bits of advice from Bob, and we had established that the motor was ok, and that as someone else suggested that I do need a 16amp supply, which will be no problem, Bob happened to be up my way and popped in today, and helped fit a Replacement DOL and Thermal overload from Tool Station.
Once again, thanks All...

Sammo

 

[Tony Spear]

expert help from a wonderful chap called Bob, over the last week there have been a number of diagnostic bits of advice from Bob, and we had established that the motor was ok, and that as someone else suggested that I do need a 16amp supply, which will be no problem, Bob happened to be up my way and popped in today, and helped fit a Replacement DOL and Thermal overload from Tool Station.
Once again, thanks All...

Sammo

That'd be Bob "9 Fingers" formerly from this Parish I assume?

Very much missed over here.................................