Certainly lots of food for thought.
Regarding millivolt testing, is it then correct to understand that the best general practice is to fault find without using the equipments supply, but by using a current limited bench PSU? Another question is, "is the millivolt testing used on all components, for example, how effective would this be on BJT's and FET's, or should they still be tested 'offline' or even out of circuit?" Or am I missing something?
I've not had any time this week for hands-on experimenting, but have a board here which is pulling the supply voltage down so shall try out the suggestions given today.
.. Had a look at the lock-in amplifiers, and yes, they are not cheap, but I'm intrigued.. Even more so that "you can whip one together for any given special purpose for under $15.00. I have done so many times"...
Where can we find details on that?
Anyway.
Thanks again all.
Onwards and upwards.
James
James55