I'm afraid that I must concur there, Robert.

It seems that (yet again) folk may be forgetting Mr.Geoff's "First Rule of Fault-Finding" ...
viz:-
Think Simple!That is, always make sure the problem is not something like:-
1) Loose connection
2) Depleted battery
3) Blown fuse
4) Lack of mains power ...
etc.... before diving into the likes of U-123, IC-456 ... or even R-78!
And even then, the next step should always be to check that all power supply voltages are "there" (and at expected - sensible - values). And that includes battery voltage(s) - both off-load and (if possible) on-load.
In my experience, faults are very rarely due to failed "chips". And, even when the chips are, shall we say,
fried, the primary fault is generally elsewhere (
eg, failed component in the power supply - which can usually be detected by that most sensitive piece of test kit:- the Mark I Human Nose).
