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Triac PC, should I fix or convert?

Posted: Mon 16 Jul , 2018 21:39 pm
by Dan-27

I'm an DT/Engineering teacher from Sheffield. The school I teach at acquired a Triac a few years back, but we were never able to make the most of the machine due to leaks in the pneumatic system. With space a premium and money too tight to repair the machine it was in need of a new home, which I was more than willing to provide!

The team at Denford were great helping me get the machine up and running again, but then the problems started. I have the machine set up in the garage, and it ran well on a basic area clearance job but after a manual tool change (the whole pneumatic system has been decommissioned) the machine started to judder, the lights dipped in the garage and the smell of burning electronics filled the air. I was advised that the 2.5mm supply to the garage may not have been able to supply enough electricity causing a rise in current, damaging the spindle drive thyristors (a closer inspection revealed a tell tale scorch mark on the heatsink). A new Sprint board was going to be £230 and a replacement thyristor £30, being a teacher I'm more time rich than money rich so I opted to replace the thyristor myself. 5 months after placing an order with Mouser my part arrived and I replaced it, applied new thermal paste to the heatsink, and upgraded the supply to a 6mm single line from fusebox to machine. It worked for about 30 seconds! Now every time I power on the control box the VOR, GOT, GCR relays click on and off and the spindle powers itself up automatically.

My question is this; should I continue trying to repair the existing control system, or would you advise buying new hardware and going for a Mach 3 conversion? Any thoughts or advice would be much appreciated.



Re: Triac PC, should I fix or convert?

Posted: Sat 04 Aug , 2018 21:44 pm
by robertpearce4
I am sure the 2.5mm wiring has nothing to do with the fault you report. An increase in load current produces a drop in voltage (Ohms law). 2.5mm twin and earth on a short cable run is good for 24 amps The spur should be fused at 20 Amps. The spindle controller/motor has nowhere near this power demand (probably 1200VA).
You need to positively identify what blew the thyristor. Probably a burnt out/faulty spindle motor or wiring. Without knowing what the exact thyristor type is I'm sure a suitable replacement is only a few quid, but there is no point in replacing it until you know the cause of the initial failure. The blown thyristor/s may have damaged your spindle controller so it needs checking out to.
I am a newby to these Millers and CNC stuff and have my own problems....... If I cannot get to the bottom of my Mint card/EuroStep I/O hassles I will be converting to....

Re: Triac PC, should I fix or convert?

Posted: Thu 09 Aug , 2018 7:47 am
by robertspark
Mach3 {or any other cnc + motion controller} are not going to solve your problem at all.

The problem sounds primary power related to the spindle by the sound of things.

so, I'd find the fuse that powers the vfd (variable frequency drive) are remove it and repower up.

the machine to test it does not need a vfd, so I'd then test all the motion.

Re: Triac PC, should I fix or convert?

Posted: Thu 09 Aug , 2018 7:50 am
by robertspark
fuse Listed as F1 here: