Mesa card 7i76e no longer has +5v

Never done any reversing polarity. The card installed in the milling machine works weil, until the day before yesterday, when the milling machine powered up, the card has not +5V

PCW wrote:

That's a REVB board with no 5V TVS, Not a lot of parts run from the 5V,
mainly the step/dir drivers you might try a lab supply or other 5V supply
,limited to about 2A and see what gets hot if left on for a bit.

 

Yes, i use another individual power supply for +5V input to P3, its voltage drops to 2.2V and current draw is 4.8A. After a while, hot parts found, as shown in attached photo, it's soldering melted, when it touched it, it came out with my finger (i.e it popped out). Immediately, the PWR orange
LED lids, the voltage goes back to 4.9V and current draw drops 0.15A, there is 3.3V observed when measured. When i switch to using +12V to unreg logic PWR IN, several green LEDs on the top of card flashs a while and also PWR orange LED lids. I haven't yet installed it to enclosure to connect all stuffs for testing. Wil it be Okay now? What spec. this C1 capacitor is, will i just replace it and get the card normal?

photo

I measure the resistance of C1 capacitor, it is zero, or short

Wow, that's pretty rare to have a failed ceramic capacitor.

C1 is a 22 UF 16V 1210 ceramic capacitor

Its probably OK with this missing as its one of three 22 UF capacitors on the 5V rail

everything gets back normal now, thanks !