Hi all,
I hope someone can offer me some advice. My Heiz Microstepper controller failed 20 mins into a g-code routine - back and forward x axis translation, repeat 50 times.
I am running Mach 3 with an opto-isolation card and the system has been working fine to date.
The main power indicator is lit and Mach 3 responds when I press the E-stop buttons, so the stepper driver board is apparently okay.

The fans aren't turning & no power to my stepper motors so it appears that the issue lies with the supply voltage circuit board.
The circuit diagram is located at this link: http://cnc-step.de/images/attachments/Downloads/Betriebsanleitungen/stepcontrolhy_eng.pdf

On closer inspection two Vishay BY500-800 Soft Recovery Fast-Switching Plastic Rectifiers were lying loose on the supply voltage board.
Not connected. The solder on them appears to be melted. Any ideas what could have caused this? I'm not an electronics expert unfortunately, but hope to get the assistance of one next week.
I'm waiting to hear back from Heiz support - they're a German company and I own a S-700. However their forum isn't very active.
Any input would be fantastic!
All the best,
Aidan

Hi Aidan,

Not much help but I have a sneaky feeling that someone has been to that power supply before you. From the circuit diagram those diodes do not appear to belong there. To melt the solder they must have got extremely hot and I am surprised that the 8Amp fuse did not blow first. I would suggest that one of the 32Volt, 5Volt or 12Volt circuits is drawing too much current but which is difficult to speculate. Try a closer examination, possibly using an eye glass, to see if you can spot any of the other components which may have overheated. Oh and check that the 8Amp fuse is actually 8Amp.

Tweakie.

Tweakie - Cheers for the input mate.
Now that you mention it, initially a technician opened it up to inspect the circuit board.
He was checking the voltages, then poked a screwdriver in to check a wire was connected.
I remember now that there was a flash and that probably did the plastic rectifiers in...soon after I spotted them lying loose and mentioned it to him.
Okay, aside from this, what's the differential diagnosis on a failed supply voltage board...?!!

Hi Aidan,

I would not be downhearted. I think that at this stage you have to assume that it is just the psu board which has failed. Luckily it is old technology and there is nothing there that cannot be fixed / components replaced at relatively low cost. It would be wise to repair the psu and test it without the stepper drivers connected initially. Then connect and test the drivers one by one in case one of those is faulty also.
If you use a technician for this try to find one who doesn't stick screwdrivers in everywhere. 

Tweakie.

My Heiz controller box stopped working the other day & thanks to this thread & google I managed to fix it. Those diodes are there on the + output of the bridge rectifier on my box even though they are not on the circuit diagram. One had become disconnected from the connection to the circuit board due to a bad solder joint. Resoldered & all is good :-)

Before the controller failed I thought the cooling fan was dying as the speed of the fan was not cosistent, I guess this was due to unsteady voltage from the failing solder joint.