[Tommangod]

Sorry if this is a dupe thread.
So I bought a CNC 3020 that had been upgraded with a G540.
Problems in order:
1. Scary hot steppers, pretty hot while just "holding"(G540 powered up only), and really hot when running even at a slow feed.
2. Blew fuses in the original PS, replaced fuses and ran at slow feed with no spindle(roadrunner).
3. Blew fuses in PS again, replaced PS with a good 24v 12A g540 dedicated one and ran again with no spindle. Still hot steppers, one stepper overheated/failed and blew the g540 fuse.
4. Closed problematic pump switch, forever. Ran leads out of fuse spot on G540 MB and into a breadboard, for fast fuse changes, that I was doing a lot.
5. Replaced blown stepper.
6. Finally looked at resistors the previous owner put in place. Pretty sure they are 3.5 amp, and the steppers are 2.0A.

So I thought I found a 2.2K resistor, and tried it. No holding or movement on the stepper at all. Tried just closing those pins with no resistor, nothing. Tried leaving those pins open, nothing.

I'm going to order some of those variable resistors now, but shouldn't the stepper at least work with no resistor, as the one I removed seems to have been allowing the full 3.5 amps that the g540 produces?

If you can't tell, I'm new to much of this. But any help would be appreciated.

I think I'll do a little thread on common issues with the 540 pump switch, faulty steppers and their ability to blow the g540 fuse.

Thanks

[Tommangod]

So the resistor that the machine had in place, on 2.0A steppers are:
Orange Green Green Brown Brown, and the internet says that is 3.5K ohm 1%(they work, but get really hot and fail)
I tried a Red Red Blk Brn Brn, 2.2k ohm 1%, best I can tell. No movement or holding

[Tommangod]

ALRIGHT, We're rocking now.
So my new 2.2k ohm fused stepper is working beautifully, fast, and cool as a cucumber.
I had it plugged into the A axis instead of the X.

So I would advise folks struggling with faults, blown fuses and really got steppers.
*Solder that pump switch closed. It's poorly designed and you need to have the case assembled to make it close, normally. Closing that switch got rid of my faults that would just appear mid run. Gone.
*Go ahead and plug some breadboard leads into the fuse holder and you will never have to open the G540, risk bending pins removing the MD from the drivers, and you can use any appropriate fast blow fuse.

Thanks, folks.
I expect to be picking your brains on some other stuff soon.

[Tommangod]

So basically, I destroyed the original power supply that came with the CNC 3020, a servo, and many fuses. I'm lucky I didn't blow the G540 beyond repair.
All because of improper resistor selection.

The steppers were drawing too many amps, and blew the China 3020 spindle/driver PS fuses first. I mistakenly went with higher amp fuses on the PS and destroyed it.
When I put the G540 on a new PS, and still ran improperly 'resisted' steppers, I burned up a stepper, and it in turn blew the G540 fuse.

everything is fine now though. But it could have been an expensive lesson on resistor selection.

[Tommangod]

So basically, I destroyed the original power supply that came with the CNC 3020, a servo.

stepper
rattled, but victorious

[Tommangod]

*Solder that pump switch closed. It's poorly designed and you need to have the case assembled to make it close, normally. Closing that switch got rid of my faults that would just appear mid run. Gone.
*Go ahead and plug some breadboard leads into the fuse holder and you will never have to open the G540, risk bending pins removing the MD from the drivers, and you can use any appropriate fast blow fuse.

I took pics when I did this if anyone is interested in a step by step.
Because when I was having faults, and looked at existing threads, I saw people forgetting that the G540 needs to be assembled to close the pump switch. And even when my G540 was assembled, it would fault, mid run, because of that Fn switch. Closing it with a glob of solder took care of that for me.
The fuse holder 'extension' I like, even though I don't expect to blow them much now. I ran the leads out through the hole where the pump switch was, and I will never have a reason to open that G540 box again.