Hi All,
THANK YOU VERY MUCH for all the help you offered me. Finally I was able to nab the culprit out. It was the MAX 232 IC. I replaced it with another one (HN232) and it was just fine.
I'd update the circuit diagram in my homepage (of 8052) so that any newbie can use it as reference (for the start).


Saji Jacob George wrote:
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the capacitors to be connected to pins 1,2,4 and 6 of 232 should be 10uF/16V or 22uF/16V.
in some circuits i have seen 0.1uF, don't use 0.1uf capacitors.
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Well Saji (guess its ok if I can call you so), thank you VERY much for the checklist and tips. Now, is a 10µF/16v the absolute minimum, cos I've already soldered the 0.1µF/63V to the PCB (because it was working fine with the test circuit). If its not too dangerous, can I retain them. Im using Regulated DC Power Supply so, we cannot expect spikes etc. (atleast they would be to their very minimum).


Please advice on what to do (regarding the value of the capacitors)...

Warm Regards,
-Harsha