Mesa 7i84 spark at field connector

I already had my field power negative connected to TB1-8, and just applied +21Vdc to TB1-1 and got a spark. Checking the resistance between TB1-1 and TB1-8 they are shorted. Have I fried my board? I dont see any obvious damage.
Mark

Unfortunately if you plugged in the field power live
its possible the 7I84 was damaged. If you have a
lab supply you might try powering the field
power with say 12V and a low current limit (say 1 A)
and see if you can find any hot parts

Thanks Peter, While wiring up the output pins a few days ago, I got a spark at an TB3 output pin. Cant really recollect the exact error chain, but it was the Festo's pin 23, which I selected by mistake, should be unused, and should not have been a short to live, although I didnt check that.

 
I'll ask at work if someone has a lab PSU. Thanks for the suggestion. Maybe I get lucky and can replace a component. Maybe not
Mark

Hello Peter,

One of the viewers here in town offer to trouble shoot it for me. Stephan took a look at it yesterday and identified that the component he pulled from here was causing the short.
 


He was not sure whether it was a TVS or a simple diode, and we couldn't identify it online, as the model number on the housing was not clear. EPJ30? What is the component part number I should be reinstalling here please?
He also had a stern word with me about using a Lithium battery as a PSU, and about not switching the power lines.
Regards,
Mark.

SMA package with R17 marking - likely MRA4007T3G

Yep, its a MRA4007 ( as reverse polarity protection)

Thanks very much Peter.