1 May
2011
1 May
'11
12:55 p.m.
I measured 8.6V across pin 1 and 8 of E2.
So the 555 timer is getting power, and 8.6V is enough to run a 555. So
why isn't the PSU working?
OK, I know what I would do next :
1) Remvoe and test (properly) the chopper transistor. It's the most
likely part to fial after all.
2) Remove the Bias and Interface Board and find some way of powering that
control circuitry from a bench suppy (or even a 9V battery). Of course
you can't then link it to the mains parts of the H7140 (like the chopper
transfromer), but now you can connect a 'scope to it and see if that 555
is oscillating, if the chopper transistor is being driven, if the
regulation feedback circuit works, etc.
-tony