Moovo Power Supply and PCB Fire Repair

I'm a happy owner of a MOOVO XA432Be swing gate opener. Worked well for years! Suddenly things changed... the wife's car get trapped inside when the power failed and the gate refused to budge. It has little plastic goodies that you can turn to open the gate, yet the Aussie sun has taken its toll and they just twist off.

A little investigation that night confirmed a power supply failure in the MOOVO, in fact the PCB had caught fire. Closer inspection revealed the fire had burned through the PCB between live and neutral, probably due to ant infestation - there were lots of them!

I can't get a replacement economically so I decided to repair the PCB . I couldn't find much with Dr Google, so this is my fix, how permanent is yet to be discovered. So far its lasted 14 days successfully @240Vac applied continuously.

[Feb 2021 Edit - well now the power supply has died again due to ants shorting components, an rather than fix it Ive installed a small standard power supply - one of these wired direct to where the old power supply connected. When I have time Ill try to fix it and/or make a box for the new PSU]

This repair is about fixing the PCB damage using glue. I don't know if its a new technique, but it certainly is to me. my Google searches did not reveal any similar PCB repair technique, although I did find some discussing grinding out the carbonised area.

Just a little background for interest...

• The gate openers generate a lot of torque. As my gates are flimsy, I had to install a home made second stop on the motors
• The PSU has a 630mA fuse at 240Vac - far too large for my flimsy gates. The PSU is supposedly rated at 250W but there's no way I believe that. Nor does it need all that power.
• The remote receiver seems to work fine at 12V
• The motors operate on and by manually injecting 12V in the correct direction on the motors will either open or close the gate.
• The second photo shows the input power polarity on the remote receiver board in the lower right corner. The backup battery power connections are at the top left.

The photo shows some of the goodies needed to do this repair. I assume you know how to solder and desolder components, and the soldering iron cleaner represents a soldering iron as well. I remembered the safety glasses, but forgot the mask - do use one when grinding the PCB!

The lamp and socket on the right may be of interest. its nothing more than a globe in series with the socket in the live leg. When testing the repair I plugged it into the socket as a protective measure - if there was a short the globe lights. A tungsten globe is needed of course.

All you need from the hobby tool kit is a burr bit.

And a good multimeter of course!

Not that any of the following matters, but for interest sake:

It appears that the ants must have bridged the relatively small live-neutral gap under the filter capacitor, causing tracking and burning that track. No other tracks were broken. The fuse (630mA) did blow, but seems to have held on long enough to heat the remaining live track enough to set fire to the PCB but not enough to burn the track itself.

First clean the board with isopropyl alcohol or other specialised PCB cleaning fluids and a small brush to clean out as much of the carbon as you can. I use a hard toothbrush. Unfortunately, the exposed fiberglass mat absorbed the carbon and became conductive - it has to go.

Make a small diagram of the position of the holes and the connecting tracks so they can be easily reinstated after the fix, then don a mask and eye protection and grind out the glass mat. Do it outside. I used a cheap ball burr in my Ryobi hobby tool taking care not to blow the glass dust around too much. The ball also allows undercutting the edge of the hole relatively easily. Make sure all the carbon is ground out, use a loupe and closely inspect the hole. When you're done, get the multimeter out and measure resistance around the hole. I got infinite resistance all around the hole and to the tracks - subject to my meter's capability of course!

I also found photos of the tracks valuable when reinstating the circuit.

Getting rid of glass-fiber dust is not so easy! I didn't want to blow it way (putting the dust in my breathing zone) nor vacuum it up (probably will go through the bag). It seemed a good idea to have a sticky paste of sorts to pick it up, so I used a damp old soft cloth with plenty of dish washing liquid to wipe it up. Works a charm! Rinsed out the old cloth and washed away all the debris neatly. I expect shaving cream and toothpaste may also work well (used to capture asbestos fibers while drilling according to the asbestos web site).

Clean the board again with isopropyl alcohol and its ready for the next step. I also rinsed the board under running water. Doesn't sound like good idea, but actually has no detrimental effect provided its dry before powering it up again.

Stick a piece of tape firmly over the hole - I used masking tape - over the hole. This is the backing for the glue. Mix up Araldite epoxy resin glue. Polyester resin will probably work too, but Ive not tried it and it can make a mess.

The epoxy is fairly thick and can be pushed into the hole simply enough. Try make the top surface smooth even it its a bit proud of the surface. Its really sticky but persevere. I found it doesn't matter if the track holes get coated as the soldering iron melts it off.

I left it to dry for a week. Peel off the masking tape, mark and drill the holes, and fit the components. Some of the tracks were removed with the fiberglass mat, so make up new tracks using wires.

I tested each of the components; none were faulty, so I have reinstalled them. Some capacitors on the board show some blackening but it isn't conductive and I couldn't shift it, so I left it alone.

So that's it. Simple enough on single or double sided PCB with large tracks.

Well, after 2 weeks of continuous operation, the fix and the power supply are working happily. With reference to the photo, there is no indication of melting or tracking across the fix. I guess time will tell.

It's of some concern that the glue seems to melt. I may do more investigation just to see how sensitive it is to heat. Polyester resin may be better and perhaps it can be applied by syringe after mixing in the hardener. Hmmm, a new Instructable in the making?

If you feel that way inclined, please vote for this entry in the Fix it contest! Thanks!