Spemos Card C1 (Power Supplying Card) Problem

Since I haven't got a clue what you're talking about: I suspect that this is a very low volume card for a specialist application, and, I bet the manufacturer has accidentally made a whole batch with an electrolytic capacitor fitted the wrong way round.

Does C1 look something like this:-

If so use a DVM to check that the power supply negative (0V) input to the board is connected to the -ve side of the capacitor (this side in the picture) and the positive input (12V?) is connected to the +ve side of the capacitor.

The capacitor in the picture is rated at 25V. I suppose it is also possible that the ones fitted are not rated at or above the power supply: say a 4.7 or 6.3 volt cap. on a 12V rail for example.

Dear .C 1 is an electronic card in Spemos(wartsila engines speed monitoring system). There are 3 other cards too in this system . the function of this card C1 is to provide smooth 12 VDC supply to all other cards. It is getting 120 V DC input and there is DC/DC converter for smooth output voltage (12 V DC)that is being fed to other cards.It does not look like you showed capacitor..I will upload the picture of the card at some other time..

Yes a photo of a burnt and unburnt card would help:-

Where is the 120V DC coming from?