KX3 Spindle Problem

[Kitwn]

I think it is the speed control board, does it have a potentiometer on it.? I think the AP stands for Analog Potentiometer Board.

The blue thing, top right hand corner of the photo is a trimmer potentiometer, possibly a multi-turn type. The label under it looks like "START/STOP". If you adjust it keep track of how many turns and in which direction so you can put it back where it was.

Edit: Just made time to read Doddy's link. START/STOP is a label on one of the connectors. The potentiometer is for the speed at max control voltage. Pots can become faulty and go high resistance but it's possible to clean the track inside by simply adjusting it up and down a few times. Certainly worth a try for the time it takes.

[dazp1976]

That board looks exactly like little machine shops upgrade board.
Was the machine bought new by you are did you buy it used? Might be the LMS board in there already. Straight swap.

[Doddy]

Okay, I've spent 20 minutes too long trying to find out what the AP2 is, and failed. There's various talks of step/dir controls on the KX3 but I'm minded not to read too much into that at this time. Can you get a photo of the board to perhaps help us understand it better?

[ModelSteamKen]

Hi Doddy
Thanks for your prompt reply. Here is a photo ofthe suspect AP2.
Hope this works.
Thanks
Ken

[Doddy]

Ugh. I wish I'd never asked, now. I'm throwing an awful, awful lot of guesswork into this that might be completely misleading.

Have you seen this link and does it look sensible and appropriate?

https://littlemachineshop.com/images...UpgradeKit.pdf

If only for the association with the board. I'm reading more, and this is hitting the territory I'm in with spindle speed control on a SX2.7. But, my interest lies if this is OEM or a modification to the KX3

EDIT: Though read somewhere that Sieg used these boards themselves for the CNC machines.

I'm out of ideas here - there's clearly two opto-couplers that are connected to the spindle-control board - these could be step/dir but that's guesswork. I would expect that these would be involved with the speed control given the nature of this board - if you had access to a scope it would fall into the "interesting" category of investigation, but you're looking at a fairly proprietary interface now between this and the BLDC controller in the Seig.

But you've convinced yourself that your analogue wiring to the board is correct?

EDIT 2: I'd check through that link and verify your wiring as a first port of call.

My experience of the BLDC board is that can be fragile (mine popped two IGBT and a fair bit of collateral circuitry early in its life - replaced under warranty), and you've suggested that you may have had similar problems and replaced the board yourself in the past. So there's a question that you have no spindle control (no rotation)... is it the BoB - you suggest not / this is replaced. Is it this board or the spindle board (BLDC controller) - and that can be a challenge to understand (sorry, that's not very helpful I know)

[Doddy]

Anecdotal footnote: When I get around to it I'm tempted to replace the whole Sieg board with a Chinese BLDC controller - they appear quite reasonable in cost, and offer 0-10V speed control out of the box. I did start looking at the start of this enforced isolation business but got distracted. I may pick up on this again.

[Doddy]

I'd tread carefully here with blindly replacing boards - the problem is not (as I understand it) known to be with that card at this time. That is what OP is asking about and unfortunately I don't know enough about that card to understand the protocol between itself and the (modified) spindle control card in the mill (the same kit, even if OEM with SIEG, requires a modified micro controller on the spindle control card).

This link provides a really interesting bit of reverse engineering which explains a bit about the protocol used on the "LMS" board (aka Sieg board).

https://blog.familjenjonsson.org/blo...olant-control/

I'm about to head to my SX2.7 and see if this is similar to the touch-panel interface (nothing is ever that easy! and I fear the LMS interface will be different)

[ModelSteamKen]

Here's an update to the no spindle rotation problem. Yes I've seen the Little Machine Shop's upgrade and now realised that this is an alternate board used by Seig to enable the speed to be altered by the BOB output. I have been in contact with Arturo at CNC4PC and he suggested that I check the wiring of the actuation circuit as everything else checked out OK. This consists of the mains feed passing through a small transformer on the AP2 board and is switched by the relay on the BOB. On investigation I found that I was not getting any mains voltage at the input to the relay in any position. Mains was found at one of the pins going to the transformer. Checking the primary of the transformer for continuity through the transformer I found that it fails( No Continuity) Followed the tracks to the transformer and when tested these were OK to the pins. The secondary circuit tested OK. That's my problem - burnt out primary winding on the transformer. The relay was unable to make a circuit and hence activate the board. So I have to get a new AP2 board from Arceuro when things free up again.I've been round the houses with this problem but at least the machine has go a complete facelift as regards electronic boards. The machine was bought new by myself maybe 10yrs ago now and it has served me well doing the bits and pieces that I come accross. Hopefully for many more years when I get this board replaced. Thanks for the pointers everyone.

Ken

[Doddy]

Oooer.

So, one experience I read (amongst many) was someone modifying the AP2 board to remove the transformer as they could feed a local 12V DC straight into the onboard regulator on the AP2 PCB. They removed the transformer and inserted 2 pieces solid-strand wire from the two primary terminals to the two secondary terminals, then removed the 110VAC (this was an American site) input to the board and sourced 12V from "elsewhere". That fed into the local bridge and onto the local 7805 regulator. That could be a very easy fix for you if you want to avoid the cost of a new AP2.

Chances are its an embedded thermal fuse in the primary that's gone.

Very useful information and follow-up. Thanks.

[ModelSteamKen]

If it's definitely 12v I think I will try and source a new transformer. RS is still online. Desolder and drop the new one in. Nothing beats a try! Could always fall back on the 12v direct supply as plan B.

Ken