I have an SX3 that keeps blowing the main fuse located next to the EMI filter, not the one on the PCB. It will blow as soon as power is applied to the machine without pressing any buttons. Any idea what could be wrong? I have checked the obvious things. The spindle travel dro isn't touching anything. I have disconnected the U - V - W motor terminals from the PCB and still the same thing happens.
I have done a visual inspection of the PCB and can't see any issues with it.
Any idea what it could be, is this a common problem?
So I have bypassed the emi filter, just connected a power lead straight to L, N and PE, removed the UVW motor leads, removed the two plugs on the PCB for the Control Panel circuit board/digital tacho & Motor control circuit,rack handle taping switch, motor control circuit, emergency stop switch.
I then bridged K3 & K4 which are the terminals for the emergency stop switch. I hear the relay click and it trips the rcd straight away.
My SX3 died at the weekend, Mine chirps / screeches from the display board - i.e from the beeper. I have been doing some research ahead of getting into the machine I found this thread really useful
Another Aussie NeilW20 posted some schematics - be aware that there seems to be 2 versions of main board .
I'm not a beginner nor an expert in electronics and don't know your level of skill either BE CAREFUL where there is mains there is the risk of electric shock /electrocution
With NO power applied -Unplug it please-look over the main board look for evidence of burning / overheating, You will probably need to look at the underside of the board too. Clearly there is a short somewhere possibly related to the IGBT-s there is info on how to check these in the above thread. Another thing is to check the Hall sensors on the motor again see the thread. Hopefully NeilW20 will reply - he really appears to know his stuff. It could be a few weeks until I get to look at mine - theres a Bridgeport clone sitting on a pallet in front of it right now - the SX3 must have sensed I was thinking of selling it !
I have checked the board and there is no evidence of burning, no burnt out tracks etc, components look fine, I even did the smell test. I removed the heat sink to get a better look underneath, it all looks good there too. Can the IGBT's be tested on the board or do they need to be removed?
Because I bought the machine in not working condition I have no idea on what happened.
I had a quick look over the thread, seems the e stop button and the safety guard can do some damage and shouldn't be used. Is it possible the relay is damaged internally causing it to short?
Thinking along the same lines as you last night I emaild my electronic engineer friend who said
"You should be able to do some checks with the IGBTs in circuit, they can fail short circuit E-C and obviously if you find the ‘G' terminal showing a low reading
to the other terminals E/C something has gone! Make sure the motor is disconnected at the output connector. Check the internal protection diodes if
you have a diode checker on your meter. Open circuit fault is more tricky and you’d probably need to remove to check that you can charge the gate
and see the device conduct.
As for electromechanical relays the usual failure mode is to go Open i.e. won't close. Anyway look at the Schematic square A3 ; the relay is a 2 pole changeover and both poles are commoned so only Live goes through it so there is no path to Earth or Neural for it to short to.
As I understand the H bridge configuration of the IGBT's there are two per phase U,V, W at any time only one of the IGBT's on a phase shout be conducting if they both do bang !
Ok had a chance to have a look at this again today. I checked for continuity on the IGBT's and the two next to the 8 pin connected seem to be shorted. I am getting continuity between E - C, G - C and E - G. They are still on the board, I probably should remove them to check them properly just in case another component is causing them to short.
Hopefully it is just the two IGBT's that have gone and they haven't taken down any other components, would this be possible? Externally these IGBT's show no sign of damage. I found some on ebay, I can get 10 for AU $33, I don't need that many, but it seems if I buy two separately it won't be that much cheaper and some spares may come in handy (I hope not!)
Problem with this board is that you have mains voltage and DC at roughly the same to drive the motor very easiy to blow It up whilst trying to fix it. If you want to keep the mill and go CNC you might be better off ditching the existing electronics and retrofitting something better. if you want to sell it on a new board in the UK is £185. Usual and best practise when working on mains kit is to use an isolation transformer - Google it re audio repair and I'm sure the explanation will be better that mine. If you are set on repair I like the idea of LEDs on the various supplies if a rail is out you will soon see and at no risk to you or the board.
After reading that thread it makes me want to give up, sounds like it's most likely would have taken out some other components for sure. I don't really wan't to spend a bunch of money and time on some parts that might not even work.
I might look at fitting a better controller to it, hopefully so I can retain the brushless DC motor, apparently they are a good thing when working.
Ok decided to have another go at this today and I think I got something positive out of it I removed the two damaged IGBT's there were shorted and decided to try and power the board up. The fuse no longer want's to blow and the orange led on the PCB lights up. All good.
So I decided to bring it back over to the machine and I plug everything back in except leave the U - V - W motor leads disconnected. Turns on and does the Beep and I get 0 0 0 0 on the speed display, all the buttons seem to work, Forward, Reverse ETC and when I turn the motor by hand I am getting a speed reading on the display. Seems pretty normal to me so far.
Tempting to buy the parts and try my luck but still not 100% sure it will work.
Well done you are making progress. That indicates to me that you have narrowed the fault down considerably. If you replace those IGBT,s and all is not well then it's likely that the fault still lilies with other components on that channel. Before you power up did you check the Hall sensors on the motor ? It would be a shame if a fault there takes out the board again.
Yeah thinking might purchase those IGBT's and give it a try, I wish there was a supplier here in Australia as getting those parts from china may take a few weeks to get here.
I haven't checked the Hall sensors on the motor, how would I go about doing this?
My board has IRFBC20 ' on it rather than your FGL60N100 - they look quite different I note also that your devices are in the process of being discontinued. The Hall tsets are in one of the threads I mention before hopefully i have attached it below
Sorry I don't have a pic right now as access to the back of the mill is difficult. I have a Bridgeport clone right in front of it that I am making a priority to install that Inhope will be an easier job than the SX3. You made me realise though that I don't know if my board has the IRFBC20 or not - I'm working off a schematic but I'm 90% sure that it's the Atmel driven one. As I understand it there have been some variations in board design. I will post the pic when I get to it but it could be a month or so away yet. hopefully you'll be up & running by them.
Yeah I checked the specs of them yesterday and they only seem to be rated at 2.2A max current, seems a bit unusual. I will probably end up ordering the parts from eBay and hope for the best.
SX3 Blowing main fuse
I removed the two damaged IGBT's there were shorted and decided to try and power the board up. The fuse no longer want's to blow and the orange led on the PCB lights up. All good.
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