Sparkologist Fault Finding from afar

[roverrescue]

So I have a geared head drill in the shop
It is a SM-MD40XP unit single phase 240VAC

Just today when I went to use it the lights are on but nobody is home.
None of the switches forward/ reverse/ coolant pump will make the spindle turn or pump run.

The work light is on and the powered up light is on but this is it.

I pulled the cover off and had a look see. Attached is the wiring diagram hiding inside the
electrical housing.

The system as far as my non electrician mind can determine uses a transformer from 240AC down to 24VAC. The 24VAC runs the work-light and is used for all switching of the unit.

The switches are momentary NO for Forward/Reverse and Stop
The safety STOP switch is NC

The 24VAC switching current feeds three relays to switch the motors (in the diagram these are KM1 KM2 and KM3). KM1 and KM2 are for the main motor forward and reverse. KM3 is for the coolant pump motor. The relays used are the Siemens jiggers - see picture attached. As you can see the relays have an over ride button.

Now the spindle does operate perfectly in both forward and reverse when KM1 and KM2 over ride buttons are depressed. But the coolant pump does not operate when KM3 over ride button is pressed.

My first thought was the safety STOP switch had failed to open so the 24VAC switching is isolated but but it seem to be working functioning.

Both 1A fuses in the circuit are passing current and test okay.

I took the multi-meter to the unit when live (carefully), it seems that when the forward switch is depressed 24VAC is seen at wire "5" indicating that 24VAC switching current is getting to the coil of the relay. (Similar finding for KM2 reversing relay).

Sooooo switching "seems" good but just no goey through to the motor via the relay.
What are the chances all three Siemens relays would fail simultaneously?
Slim I would say?

Obviously I am missing something and quite likely no one has enough information to help but...

Any suggestions would be appreciated before I call in a sparky. BTW unit out of warranty, and unit is too big to economically send any place for repair.

I can grab a photo of the electrical housing if that is of help.

I know this is kinda of like trying to diagnose a rattle deep in an engine via the inturdnets but hey its worth a shot...

ps looking at the diagram with rum still hasnt given me any clues...

Steve

[Blknight.aus]

I suspect you have a high resistance joint in the wiring on the neutral line between km 2 and km 3.

it will be allowing enough current to pass for the transformer to work to a point, but not enough to energise the contractors.

When you over ride them as the path to neutral is still valid for km 1 and km 2 they will allow the main motor to run, when you manually operate km 3 there is no valid neutral so the amps have nowhere to go, both sides of the motor are at active potential.


But that's just my first guess.

[Mick_Marsh]

So, are you saying the spindle turns when you press SB3 or SB4 and the pump doesn't run when you switch SB5?

[roverrescue]

Thanks Dave Ill investigate that (I assume you mean in the 240VAC nuetral line)

Mick, the trouble is I dont know enough details from the diagram.
My thoughts were that SB3 / KM1 represented the 24VAC NO switch on the console.
Or is the diagram such that SB3 represents the over ride function of the relay?

I also cant find SB1 or SQ1 or SB2 Im guessing they are switches???????

Motor spins appropriately when forward relay (KM1) is over ridden (little press button in picture attached next to 53E) and reverses when reverse relay (KM2) is over ridden.
But hitting the proper 24VAC NO switches nothing happens.

Thanks

Steve

[roverrescue]

Dave,
just did some more looking and thinking
I like your assumption - I had thoughts the transformer was bunk but is is making 24VAC across lines 12 and 0 on the diagram. But as you say it may not be making goodly current????

Oh this problem is very new - have been using drill daily for two weeks. Yesterday would have used it for a few hours total - today turned it on at power point and voila not working. No smoke no noises just no worky.

Steve

[Ancient Mariner]

Steve Disconnect the 24 from the worklight and connect to the contactor direct and see if it works


Noel

[bee utey]

My gues is that if your work light is working, you should be able to test for breaks in the common neutral line between the lamp and all 3 relay coils. With the power off you should see very little resistance between the four points at the bottom of the wiring diagram. It's probably a common screw connection that's a bit corroded. If you run a temporary wire from the low side of the transformer to the low side of the relays all should work as normal.

[Vern]

Are they 24v coils on the contractors? How's your multi meter skills?
Stick your meter on A1 on the motor contractor, press the go button and what does it read?

[Ancient Mariner]

Don't contractors install contactors ?

[Vern]

Stupid tablet and its predictive text! You know what I mean