Lathe diagram - loose wire from fuse

Hello!
I'm trying to troubleshoot a friends Lathe and it looks as this pictures.

The green wire came loose (traces backwards to heatshrink / brown wire- connected to the fuse.

Does this comes from the direction selector (See pic) or does it attach elsewhere?

Could it be connected to the RPM dial?

The diagram does not looks to be the same as the real photo?

Edited By Niclas Oberg on 07/07/2021 19:27:03

Have you got a potentiometer with a switch on the back of it?

it looks like the live out of the fuse goes to teh light and the switch on the back of the pot

Yes, the lathe is a CJ0618A

UPDATE:
I spoke to him and he said it broke when he turned the potentiometer, and blew the fuse...

So you might be right there, ill have to open it up again and examine the potentiometer that regulates speed.

It is OFF -> Increase RPM

Edited By Niclas Oberg on 07/07/2021 20:01:57

Edited By Niclas Oberg on 07/07/2021 20:02:34

more pics of the potentiometer

Edited By Niclas Oberg on 07/07/2021 21:31:58

Just a guess, but have a close look at the orange switch top right in the first photo. I think it's a double pole mains switch and the green wire goes to a tag hidden underneath. If so, the clear plastic sleeve may still be on it. The brown wires connect to one terminal and are are hiding the other.

Edited By SillyOldDuffer on 07/07/2021 21:42:55

I have a cj18a lathe and have a few photos of the control box and wiring but not in enough detail to show what you are looking for.

The end of the green wire looks a bit strange - it doesn’t look like it has been in a terminal. Does it look like the end has broken away from a soldered tag?

If so, it could have broken away from the switch terminal on the end of the pot. The one with the white wire to the indicator light.

You really need to trace the wiring from the mains incoming cable through the various components.

Note that on some of these lathes, the switches and fuses are in the neutral and not the live as they should be.

Stuart

Edited By Stuart Smith 5 on 07/07/2021 22:05:50

Have a look at the E stop the wire ends look similar and may have come from there and there is a wire going to a fuse there.

David

Not sure why I cant edit the post that has same pic 2 times but this one was supposed to be there...

The green one from fuse could possibly have been attached to the white wire to the right as there is some wierd solder there... the green one is tinned so possibly soldered in place somewhere.

If this one is to be on the switch it is the one marked L on schematic.

L is also to light and FUSE While L2 goes to the directional switch (RED)

Time to solder the wire to the switch and install a new fuse and hope it works...must source the fuse 1st
 

Edited By Niclas Oberg on 07/07/2021 22:53:39

OK!

Sorry for not posting in a long time, now the mini-lathe is in my garage so I can work on it when I have time.

To make things easier on the diagram.

jb01-15/2 saftey switch (connected to the clear shield)

jb03-12/2 emergency switch

zh-a CW/CCW selector

W4.7K OFF & RPM potentiometer


So...the wires...

Mains comes in a black cord (Blue, Green and Ground) from left in my 1st picture above
GND is screwed to terminals

Blue and green goes left into a black cord. A brown lead goes to the transparent shield (jb01-15/2) returns as blue and goes to 1 side of the fuse.
The other side of the fuse is brown, soldered/joined with a green wire. (the one that came loose)
This one connects to L on the schematic.
L is also connected to the status light, white wires from L on the ZH-A selector.

So my loose wire should be reconnected to L and that means resoldered on the switch-side of ZH-A along with 1 side of the status indicator.

So did this work?


Well....almost ...

I replaced the fuse, soldered the wire and started up...

RPM digits flashes all digits a brief second and then shows 0

All good I assume as the chuck is indeed at 0 and not moving.

So I select L as in turning mode and twist RPM from 0 to something RPM, but meter says 0 and nothing happens...


So I assume more things are broken...like main board or the ZH-A potentiometer...

More testing with a multimeter must be done...

I think the green could be the earth side of the potentiometer. P3 from the photo and diagram. A lot of that looks like a low voltage preset speed control. I would first check the earth chassis to the broken lead with a multimeter. Then trace the circuitry through the mains to the circuit boards.

I had a lathe once that had a green earth lead that was not connected from new but too long ago to remember the make.

I doubt that this one is ground or earth, as this one goes thru the fuse...it is one of the main leads on incoming power.

Soldered to L (back of the pot) the display lights up but I get no RPM when I turn the knob.

From the picture in the first post, the loose wire goes to the fuse yet the other terminal of the fuse has a blue wire which appears to go out of the box where does that wire go to

Yes. From the fuse you see a blue wire. It goes to the transparent shield covering the chuck.
It comes back as brown (in the same black cover) and goes to the E-stop (Mains In)

So the other end of the fuse (still 220V) needs to power something.

Wonder if I'm on the right track with L2 on the rotary encoder (CW/ OFF/ CCW)

Actually...the indicator light is connected to 1 side of the E-stop, currently being joined with a blue wire.

The other end of the light (both are white wires) goes to the L-position of the W4.7K pot (off/RPM)

So should the loose wire as that side of the fuse is connected to L on the diagram.

So if this does not work ( i already tested it) Something else must be broken to prevent the motor from start spinning.

+1

Looking at the circuit the dangling wire is circled in green, and it connects to switch JB01:

I believe JB01 and JB03 (circled in blue on the circuit diagram above ) are mounted together in the Emergency Stop assembly. In the large yellow box on top, JB01 is operated by the big red button, and JB03 is the orange box below (circled in red, top-right):

Pretty certain the dangling wire is nothing to do with the pot or the Forward/Reverse switch.

Be nice if the green wire had fallen off and shorted the fuse, thus explaining the fault, but the circuit diagram shows the dangling wire just safely removes mains Live from the fuse.

I fear the control electronics have failed and the green wire fell off when the control box was opened up. It has to be reattached to JB01, but the green wire is nothing to do with the original fault.

I'd check the motor with a 12V car battery - it should spin slowly. If the motor's good, I'd replace the board. In theory I have the tools and knowledge needed to diagnose and fix the board, in practice I've lost interest in fixing electronics. Others thoroughly enjoy mending broken electronics.

Dave

Edited By SillyOldDuffer on 15/03/2022 12:11:02

Am I imagining it, or is that loose green wire in the first photo connected to a brown wire?

You are correct, it is soldered together with the brown and secured with heatshrink.

it traces back to that side of the fuse

Follow backwards thru fuse is the blue wire and it goes to the safety latch on the transparent cover - returns back in the same black wire as brown and on to the e-stop.

Has this been answered yet? Can't be bothered to read this lot

According to the circuit diagram, the green wire should go to live via the fuse, probably where it enters the switch.

Disconnecting the green wire will kill the little green light above the fuse, nothing else.

There must be something else broken as well...most likely the 1st sparks made a shortcut in circuits.

No matter what I try I end up blowing yet another fuse and triggering the protection switch in the mains fuse box.

So I deemed this a dead one and told my neighbour that we (I) cannot fix it without replacing more parts or even the mainboard.

I will replace the motor with a brushless version and use a RC speedcontroller for it...along with an arduino sending PWM signals as well as receiving RPM signals from sensor and show it on a display.

Thanks for your inputs, I learned a few things about reading schematics along the way.

That green wire looks very wrong.

It's not the same colour as the other green wires, and why extend a wire in that way in the factory?

Looks to me as if someone has had a fiddle with it at some point...

Neil