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Suresh R
12/19/05 05:13
Read: 742 times

#105518 - Trouble shoot
Responding to: Andy Neil's previous message
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.

thanking you,

List of 33 messages in thread
Add on card programming      Suresh R      12/07/05 03:11      
   please clarify      Jan Waclawek      12/07/05 03:35      
      RE: please clarify      Suresh R      12/07/05 04:35      
         (E)ISA addressing      Jan Waclawek      12/07/05 04:48      
            IOW and IOR      Suresh R      12/08/05 04:52      
               not explicitly      Jan Waclawek      12/08/05 06:02      
                  IRQ in EISA slot      Suresh R      12/09/05 01:05      
                     interrupt      Jan Waclawek      12/09/05 02:21      
                        QBASIC programming      Valentin Angelovski      12/09/05 04:53      
                           reply      Suresh R      12/10/05 04:10      
                              DIP Switch Address Setting in EISA card      Suresh R      12/12/05 03:10      
                                 DIP switches...      Valentin Angelovski      12/12/05 03:55      
                                    card design enclosed      Suresh R      12/13/05 02:10      
                                       comparator      Jan Waclawek      12/13/05 02:30      
                           QBASIC live and well.      Charles Bannister      12/12/05 11:12      
                              NT - not quite      Andy Neil      12/12/05 16:16      
                                 timing in Win?      Jan Waclawek      12/12/05 16:21      
                              QBasic Lives!!!      Valentin Angelovski      12/12/05 17:24      
   refer to 'Barry B Brey'      Abhishek Singh      12/07/05 07:39      
   EISA Bus interfacing      Valentin Angelovski      12/08/05 15:54      
      beware if (E)ISA bus books      Erik Malund      12/09/05 08:11      
   Try this?      Andy Neil      12/14/05 15:16      
      Power resistor selection      Suresh R      12/16/05 04:52      
         dont do it      Erik Malund      12/16/05 06:39      
            LM317 is an option      Abhishek Singh      12/16/05 07:46      
               Wasteful!      Andy Neil      12/16/05 09:34      
                  if op can...........      Abhishek Singh      12/17/05 07:16      
                     Power!      Andy Neil      12/17/05 08:27      
         basic Ohm's law      Andy Neil      12/16/05 09:40      
            Trouble shoot      Suresh R      12/19/05 05:13      
               heating      Terry Lingle      12/19/05 07:08      
                  Reply : Heating      Suresh R      12/20/05 04:29      
                     if you refer to D4 then      Erik Malund      12/20/05 06:12      

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