Hi Jose,

Thanks for your suggestions. 

> I'm guessing you replaced a dead 628 with a 628a in which 
> case you probably 
> did not have enough protection from spikes and noise towards the 628.
> You mention you inserted bypass caps, but have you also 
> thought of putting 
> blocking inductors? Using L and C in the right combinations 
> should work.
> 
> Hope the above suggestions help.

I think, I should clarify a few points. I replaced the PIC, not because the old 628 was dead. I merely wanted to try out the newly bought 628A. Since I found it highly sensitive to noise resulting in unsatisfactory operation, I put the original 628 back and now the circuit is working perfectly, as before.

In my circuit, two of the five devices controlled are fluorescent lamps. When one of these two lamps is switched on, the noise creates the problems mentioned earlier. I have used only .1uF caps so far. I will try out your suggestion of using L and C in the right combination.

At present, it is very easy to resolve the issue by using 628 instead of 628A. But I feel, my circuit design should ensure that it works flawlessly even with a PIC that is more vulnerable to noise.

Regards,
Bala

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