Hi all,
I'm looking for tips and tricks for millivolt fault finding.
I recently ran a long thread whilst finding the solution on a TEK 466 power supply section, and in that thread various members suggested using a millivolt meter to locate the shorted components, and I know the details are already in that thread, however it would be good to have a short compacted thread with all the relevant information.
Apart from the minor detail of not having a miilivolt meter at the time, I struggled to visualise how to know that the component under test wasn't part of rail without any issues? The 466 interface board is a sea of components with six different voltage rails intertwining as the circuits weave their way to the other boards. For example a zener diode from the +5v might sit side-by-side on the board with an identical zener diode from the -8v rail.
Anyway, there is now a 0.xxx range millivolt meter in the toolkit and I am up for another learning curve, so it would be seriously appreciated if we could clarify a few points.
The fact that any shorted or failing component will show the lowest voltage across it is understood.
What is not so clear is whether people differentiate between rails (by colouring-in components on a print, for example?) or just measure across every component on the board? Thinking beyond Tek scopes, some components measure low anyway (a 0.12¦¸ resistor would be one), although they would also be marked as such, but surely there must be short-cuts to avoid measuring 500 components on a packed board if the rail at fault only has 50 in total?
Therefore if anyone can add anything to speed up miilvolt fault finding it would be great.
Thanks in advance,
James
James55