Hello all,
I am experiencing a trouble(as described below )with my new PCB .
Iam in need of few ideas to sort it out.

I have designed it as follows.
Two layer PTH PCB.
GND nets (that connects all components GND pins) are connected to the bottom layer copper pour and this GND net leads to the Transformer centre Tap.
Iam using a 12V/3A transformer which is rectified and given to 7805. The 7805 powers the micro,2 led's and 8 relays(each relay coil takes 6mA. No loads were connected at the relay contacts when i tested.

Now, the Problem i face with the board is ,
The Transformer is getting heated up once it starts powering the board.(It powers the board through a 3 pin Molex connector).

i managed to measure the rectified DC as 18VDC , and the o/p of 7805 as 5VDC and the same at micro power pin.

but the micro is not working and seem to be in the OFF state. but it executed well when i tested it with the LED's by using the same transformer(a seperate circuit i used for testing its o/p).

I checked for the shorts and any disconnect but nothing like that could be found.
Since i worry if there could be anything wrong with the way i designed the board iam in need of your valuble suggestions to help me trace the problem.

the PCB design in PDF format can be seen using the link below for your reference.


http://www.8052.com/users/Suresh/pcb1.pdf

thanking you,
-suresh.