Thanks Kai, you are most kind. I liked your appraisal of the fault- I think you may have hit the problem on the head. It's always interesting how the least understood item gets the blame first! In this instance the ADC. With fuel injected cars - it's the ECU. With my experience in lighting control systems, I had experienced electricians blaming my light dimmers for a light not working - the root cause - a blown light bulb. Another instance was the earth leakage breaker tripping on one of my dimmers - replace the breaker, same fault, 'must be a faulty breaker' said the electrician. Root cause was the water fountain leaking water into the electrics. It's a very human condition. I think we have all suffered this!

In Raghu's instance, the poor ADC was hung before being proved guilty!