I managed to smoke quite a few dollars worth of gear - twice. Can someone give me some advice?

Thread Starter

boydage

Joined Oct 7, 2016
65
I have a DIY CNC Router in my workshop. I actually use it for my joinery business. To clarify, I am an electrician with some very slightly above basic electronic skills.

What I do not have is the proper sense to megga a shield wire...... I installed a new 2.2Kw Spindle onto my router. Looking at the settings on the VFD, I decided to ramp up the start time. All was great. Until I had the CNC computer running at the same time. The next time I hit start on the spindle, everything, and I mean everything cut out. Thinking I had somehow induced a large surge into my system, I installed my spare, computer, control board, 4 drivers into my control area. Having three phase in my workshop, I plugged my spindle into a different outlet, one I have on a separate phase. Boom.

Long story short, I have a braided jacket covering the 3P lead that runs to my spindle. Somehow, and I couldn't see it by eye, one of the hairs from the braid was touching a phase wire inside the end of the spindle. Discovered with a meter. So, gutted that I had something dangerous in my workshop (not cool) but also gutted that I have smoked two computers, one monitor, 8 DQ542MA drivers, 2 breakout boards, ummm - thats it.

So back to my original decision to post. The attached picture is of the inside of a stepper motor driver. Its a DQ542MA. They are about US$40pc. I have put 230vac directly into the low voltage side - and I will need to work out exactly where because the BOB has optocouplers protecting it. Although the 230vac went onto the ground connection.

The drivers green LED comes on. But no longer works. Given that exactly the same fault has happened to these, I feel its worth having a go at repairing. But I need some help. Anyone up for the task with a bit of advice? Far out, I have no idea where to start.
 

Thread Starter

boydage

Joined Oct 7, 2016
65
To add, I was just given a 10x magnifying glass to help my eyesight and found the very small smd resistors on the input side are smoked. I will replace them for a start.
 

dendad

Joined Feb 20, 2016
2,990
I'm so tempted to say "quit smoking, it is bad for you" , but I'd best not ;)
Can you post a photo.
If you are lucky, it may just be the resistor and maybe opto isolator dead. But look for tracks blown off too. And the other inputs are probably the same circuit so there is a way to get the values.
But pictures please, and some nice good close ups if you can get them.
 

Thread Starter

boydage

Joined Oct 7, 2016
65
Hi. There are a few things we would like to think we have learned since being young (teens to 20s). Those two things were, "Listen to people with experience" and "try to learn from mistakes so you dont make the same one twice". Ha. I was gutted when I heard the little click followed by silence when I smoked the second lot of gear.....

Im not sure if there is a eureka moment when we are learning electronics. But I looked at this board, and saw a what I think is an optocoupler with a little smd resister sitting next to it. Almost the same as the setup on the breakout board that accepts the inputs from the machine to the computer.

Its what electronics is all about huh, ones and zeros, and transferring the ones and zeros from different areas protecting each other from higher voltages with semiconductors. So if all is well, the optocoupler should have done its job, and protected the rest of the board, correct or close?

The SMD resistors have 2200 on the top of them, a good one measures 220ohms - the little burn is a good sign, coupled with open circuit. The optocoupler has F 2531 1249T1 written on it. Would I replace this with a HCPL-2531?
 

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dendad

Joined Feb 20, 2016
2,990
Check D1 as well. It may be shorted.
See if the replacement resistor and diode fix it for you. The other opto may be the same, but try the small parts fix before the opto. You may be lucky.

As for we should have learned... I recently got a µBITX general coverage HF SSB/CW transceiver kit. When I built it into a case that had an old EPROM programmer in it, I could not be bothered putting reverse polarity protection in. I will never plug it in reversed! Well, a 7AH Gell Cell battery connected the wrong way can let the smoke put quite well. You would think after 50 years of playing with electronics...
It has the protection built in now!
 
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