"as i give it to power circuit the MC 8051 turn off "

The right phrase is MC 8051 Burnt off going by your description.

For heavens sake dont plug in the other 8051 - or have you already done it ?

And from your description that is all the help you will get.

Unless you tell more about the interface between the 8051 pin and the "power circuit" that you are talking about no guidance is possible.

( Is the place that you are now working insured against fire ? Just thought will ask you .)

Raghu