MESA 7I76e power shorted

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02 Jan 2022 21:40 #230575 by Jalapeno56
I'm a newbie with cnc, but good with electronics.  This is my first go at building a cnc plasma cutter.  I am using a standard 24v power supply hooked to pins 5 & 8 on TB1.  Upon first time power applied, my power supply showed .83v, indicating a short.  I disconnected power and began troubleshooting, ending up having everything disconnected and I still show a short of .1 ohms between pins 5 & 8.  No led's have lit up, all jumpers are in correct position according to info I found on this site.  W1 in left position shows short, W1 in right position does not short pins 5 & 8 but still no led's lighting up.  The board shows no burnt marks and I never saw or smelled any magic smoke.  This is a brand new board from Portugal (USA  was out of stock). Any ideas or power side schematic to help me get this fixed?

Thanks! 
Bryan

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02 Jan 2022 22:52 - 02 Jan 2022 22:53 #230588 by tommylight
Replied by tommylight on topic MESA 7I76e power shorted
The power supply wires were reversed.
 
Last edit: 02 Jan 2022 22:53 by tommylight.

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03 Jan 2022 00:03 #230595 by Jalapeno56
Replied by Jalapeno56 on topic MESA 7I76e power shorted
No sir, I just triple checked that. I even checked the output with a voltmeter in case the labels were wrong.

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03 Jan 2022 00:12 #230596 by Jalapeno56
Replied by Jalapeno56 on topic MESA 7I76e power shorted
Does this mean the board is not fixable?

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03 Jan 2022 00:37 #230599 by tommylight
Replied by tommylight on topic MESA 7I76e power shorted
It is either that or you wired the power while the power supply was on.
You might want to wait a bit for PCW to see this, he is the owner of Mesa and a valued member of this forum, he is also extremely helpful.

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03 Jan 2022 01:02 #230600 by PCW
Replied by PCW on topic MESA 7I76e power shorted
If the short between TB1 pins 5 and TB1 pin 8 is only there when W1 is in the
left hand position, either one or more of the output driver chips are damaged
or the field power TVS diode has been damaged.

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03 Jan 2022 02:56 #230611 by Jalapeno56
Replied by Jalapeno56 on topic MESA 7I76e power shorted
Thank you for the input guys! I guess I'll get a new board ordered tomorrow

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