Help - bandsaw on the fritz

[Ironballs]

Hi All, went to use the bandsaw today to carry on the tenon cutting job I had been doing on it last night. Turned it on and nothing, there wasn't the usual clunk (I assume a relay) when you hit the power and there was no resistance to the on switch.

Tried all the possibilities like safety switches, fuses etc and still nothing. When I turn the power on there is a very faint buzz from the control box that houses the switches, however that is where my knowledge of electrics finishes.

It's a big old SCM Minimax and I'm after any tips for what it could be (and serviceable by me with a screwdriver!) or failing that does anyone know of any machine electricians in the West Yorks area - as I imagine your average sparky is not going to be interested.

Thanks for any help - I need to get the old fella up and running ASAP as it feels like I've lost a limb

Cheers

Damian

 

[Digit]

Any sparks should be able to help Damian. Any pics of the type of starter?

Roy.

 

[MickCheese]

Are you able to bridge the starter? If the machine then works you know it is the starter.

Do you have an airline? Give it a good clean, it may just be dust.

Mick

 

[Ironballs]

Thanks chaps, I did the cleaning out thing and nothing. I don't think it's the starter as the relay doesn't clunk when you turn the machine on at the plug and the start button has lost it's resistance - like when it's turned off.

I'm trying to track a machine repair chap as local sparkies are very hit and miss, one I called out didn't even want the job (a simple wiring job) because he didn't fancy it. The guy that did do it was pretty expensive for what the job was, so pretty wary of sparkies

Read Alan Holthams article about electrics in the latest F&C, it could have been written in Greek for the sense it made to me

 

[big soft moose]

you need to consult the oracle (bob/nine fingers) unfortunately he has very irresponsibly gone on holiday ... you just cant get the staff these days :lol:

i think hes back on the 29th

 

[DavidE]

Hi Damian,

Can you take a picture of the offending item?

Also have a look for any buttons for a thermal overload reset. On some controllers the reset is made by pressing the stop button. With all that you've been doing I guess you'll have probably done that anyway.

Are the buttons separate to the box with the relay in?
I can hopefully point you in the right direction of things to check. Do you have a multimeter you can use?

Cheers
David

 

[Ironballs]

I'll give that a go, I've pressed every button I can see, but there may be others. Power seems to come into the safety switch and control box and then off to the starter and motor.

As far as multimeters go that's a no, electricity is like witchcraft to me and my knowledge goes as far as changing a light switch or plug socket

 

[OldWood]

OK guys - let's think this one through.

Two puzzling bits of evidence - and a picture of the control box would help.

1 There's a slight buzz (hum I take it) when the power (see my query on this further on) is switched on - Damian won't be aware if that is normal or not, but it does suggest some coil is getting power to it, but why?

2 The start button has lost it's feel - "there was no resistance to the on switch. ". This would suggest that the armature of the contactor is stuck in which is unrealistic (?), or that the start button has broken and lost its extension that pushes the armature in, but then why the 'buzz'?

Thinking about the stuck in armature, one possibility is that the armature is stuck in but the overload trip has gone, and that the cover needs to be removed to reset it - the removal being a possible safety feature such that a technician can only do the reset.

Damian - a thought.
Listen for the 'buzz', making sure it is from the Start/Stop control box, and press the STOP button. Does the buzz stop and then restart when the STOP button is released ? The STOP button operates a switch that breaks the circuit to the contactor (relay in your words) coil; there is another switch in series with this one which opens when the moving part (the armature) of the contactor is released by the coil, so the STOP is a momentary action but the armature switch is the one that permanently switches off the coil. If the armature doesn't move .... well I'm sure you can see what you're testing for.

And can you clarify please - "..wasn't the usual clunk (I assume a relay) when you hit the power" and "When I turn the power on there is a very faint buzz..."; you use 'power' I suspect in two different contexts. Can you confirm that the first one is when you hit the START button (ie power up the motor), and the second is the mains power switch on the wall ? By the way is this 1 or 3 phase and what is the motor power?

I take it that there's no one here in the Huddersfield area who is electrically savvy ?

Rob

 

[Digit]

The reason I asked for pics Rob is that I suspect the unit is a separate contactor with separate on and off buttons, and your No 2 would be high on the list for checking.

Roy.

 

[OldWood]

Yep, a photo would be a major help.

Another option I've thought of is the armature has moved out enough to clear the motor contacts before jamming, but the coil hold-in contact has not been cleared, hence the hum. The jam is sufficiently tight that the coil cannot overcome it and pull the armature back in again.

Damian - despite your worry about electrics, make sure that the machine is isolated from the mains, and see if you can take the cover off the control box, (making sure you put any screws in a safe place) - a photo inside will help us even more !

Rob

 

[Ironballs]

Thanks chaps and appreciate all the advice, the actuator sounds like it could be a possibility. I've managed to track down a local repair man (that was a job!) who's coming out at the end of the week and should hopefully sourcde the problem. Will let you know

Cheers

Damian

 

[Ironballs]

Rob - get a gold star, coil had burnt out in the control box. Standard part so should be up and running again in time for the weekend

 

[OldWood]

Damian
I actually didn't get to a burnt out coil so your award of a star isn't quite deserved !! As is the way of these things you tend to think up all sorts of more complex scenarios, but not having met a coil failure before it wasn't one I thought of. But I will remember it as a failure option in future.

If you had reported that the 'smoke (or the smell) had got out' then the diagnosis would have been more accurate; 'smoke', and come to that the smell, is desperately important for the continuing operation of electrical equipment - let it escape and you're in deep doo-doo!!

Very glad you're near enough back on line.

Cheers
Rob

 

[Ironballs]

Yes the nose and looking for blackening are always a good one when hunting for issues, even when he whipped out the offending item there were none of those signs. Maybe it whimpered out!