Disaster

[Raypat]

I received my controller board for the igaging digimax scales a few days ago. After carefully mounting two mini usb breakout boards and the controller board in a plastic box I soldered them up checking and re checking the connections. When it came time to power it up I was confident everything was connected correctly. I am only using two outputs because I do not have z axis dro at the moment.The only doubt I had was the polarity of the power supply as I had to source a different connector to suit the board. I connected positive to the centre of the plug and tested it with a meter. The voltage polarity seemed correct with a positive reading so I powered up the board. Everything worked as expected with the three leds flashing. Just to be sure I put a meter across the output voltage to the scales. With the red lead of my meter to 3v and the black lead to ground I got a negative voltage at this point. Thinking I had the polarity reversed I quickly unplugged the power supply and reversed the leads to the plug. You can guess by now what happened next. On power up I got instant smoke and the board is now dead. My question is can the board be repaired by me (a machinist rather than an electrician) or have I made a hundred buck mistake? Also is it to be expected to get a negative voltage at the output to the scales? Thanks in advance to anyone who can help.

[Yuriy]

I received my controller board for the igaging digimax scales a few days ago. After carefully mounting two mini usb breakout boards and the controller board in a plastic box I soldered them up checking and re checking the connections. When it came time to power it up I was confident everything was connected correctly. I am only using two outputs because I do not have z axis dro at the moment.The only doubt I had was the polarity of the power supply as I had to source a different connector to suit the board. I connected positive to the centre of the plug and tested it with a meter. The voltage polarity seemed correct with a positive reading so I powered up the board. Everything worked as expected with the three leds flashing. Just to be sure I put a meter across the output voltage to the scales. With the red lead of my meter to 3v and the black lead to ground I got a negative voltage at this point. Thinking I had the polarity reversed I quickly unplugged the power supply and reversed the leads to the plug. You can guess by now what happened next. On power up I got instant smoke and the board is now dead. My question is can the board be repaired by me (a machinist rather than an electrician) or have I made a hundred buck mistake? Also is it to be expected to get a negative voltage at the output to the scales? Thanks in advance to anyone who can help.

It's not normal to see negative voltage across the scale power supply. It's unlikely that that was the case because power LED, microcontroller etc. are on the same rail and the would not work with reversed supply voltage.

The board is pretty easy to fix if you have a way to desolder SMT parts. You likely blew the voltage regulator (unless one of the caps blew up). You can send the board back to me and I can fix it for you or you can buy LM1117-3.3 voltage regulator and replace it yourself. I use Texas Instruments but this part will work as well: AMS1117 3.3v Voltage Regulator IC SOT-223 - Pack of 10 D14-1. 

If you haven't read this post: Connecting iGaging Scales to TouchDRO Controller , please do to make sure you connect the scales correctly. 
Let me know if you need more info/help.
Regards
Yuriy

[Raypat]

Thanks Yuri. I would very much appreciate if you could fix this board for me. How do I get your address details for sending the board back? My email if you need it raypat8@bigpond.com

[Yuriy]

Thanks Yuri. I would very much appreciate if you could fix this board for me. How do I get your address details for sending the board back? My email if you need it raypat8@bigpond.com

Raymond,
You are WAY on the other side of the world; sending the board back and forth will be a bit expensive and slow : I have a few boards with blemishes (scratched solder mask, etc.) that I can't sell. If you don't mind your board not looking perfect, I can send you a new one if you cover the shipping (it was $13.06 last time). Let me know if that works for you.
Regards
Yuriy

[Raypat]

Thanks Yuri. I would very much appreciate if you could fix this board for me. How do I get your address details for sending the board back? My email if you need it raypat8@bigpond.com

Raymond,
You are WAY on the other side of the world; sending the board back and forth will be a bit expensive and slow : I have a few boards with blemishes (scratched solder mask, etc.) that I can't sell. If you don't mind your board not looking perfect, I can send you a new one if you cover the shipping (it was $13.06 last time). Let me know if that works for you.
Regards
Yuriy

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Yuriy,
That would be most welcome. I will try and pay $15 us to you via paypal. I will let you know if I have trouble paying. Thanks

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$20 us sent via paypal. I added a few dollars in case paypal charges you a fee. Thanks for your help.Regards Ray

[Raypat]

Yuriy. I had a close look at my dead board and it appears you are correct. The voltage regulator has a tiny hole burned through the top. I tried to buy a voltage regulator to have a go at repairing my board. I cannot find one of the texas instruments ones here in Australia and the alternative you suggested is $0.99 cents for ten but the shipping is $14us. The chinese ones on ebay are designated 1117 3.3v 1A sot223. Not 1C as in your recommended replacement. Will these work? I would like to have a go at repairing the old board just for my own education.

[Eskimo2k]

I hate it when the magic smoke escapes!!!

Ray, if you have a breadboard, the easiest way to find out is to put the replacement on a breadboard, then wire it up (capacitors and resistors) per Yuriy's schematics. If you see a solid 3.3v output when you vary the source voltage, it should be good.

Oh, in case a random reader didn't know, EVERY thing runs on smoke. Once you let the smoke out, it will no longer work!

[Yuriy]

I hate it when the magic smoke escapes!!!

Ray, if you have a breadboard, the easiest way to find out is to put the replacement on a breadboard, then wire it up (capacitors and resistors) per Yuriy's schematics. If you see a solid 3.3v output when you vary the source voltage, it should be good.

Oh, in case a random reader didn't know, EVERY thing runs on smoke. Once you let the smoke out, it will no longer work!

Ray, 
Sorry for the late reply. I threw in a couple of regulators with your board. 
Regards
Yuriy

[Raypat]

Thanks Yuriy. I didn't have any luck repairing the old board using a salvaged voltage regulator from an old printed circuit board I had laying around which had similar markings and size. Will try again when your package arrives. Thanks Eskimo2 for your advice.I will have a play along those lines.