26 Jan
2022
26 Jan
'22
10:27 p.m.
The guys at RICM have seen a problem with these supplies that if the output
cap is bad it won't start switching properly. It goes into a mode where it
acts as a linear regulator. As far as I remember they the a spice
simulation that also indicated this when the output cap had low
capacitance.
Do you see switch pulses coming out of the 723?
As suggested earlier it is a good idea to have a real AC source that is not
going to fold back when you put some load on to the H745.
Does it switch correctly with less load?
/Mattis
Den tors 27 jan. 2022 kl 00:42 skrev Rob Jarratt via cctalk <
cctalk at classiccmp.org>:
I am trying to test a couple of H745 regulators with a
DC bench PSU and I
am
having some problems with testing them.
My bench PSU is a twin unit so I can supply the +15V required as well as
the
"AC" input using 20VDC from the other half of the bench PSU. The problem is
that I don't think the bench PSU can supply enough startup current to allow
the regulator to run. It can only supply 5A max.
I have seen with the H744s that if I put too big a load on them, then they
can't start because of the heavy startup current required. I can start them
with a lower load and then add load once the regulator is running without
breaching the current limit of the PSU.
With the H745s I have tried reducing the load to see if I can get them to
start, but a 10R load appears to be too much and the regulators draw the
full 5A without outputting -15V.
I have two H745s, both exhibit the same behaviour. I suppose they could
both
have the same fault, but I am inclined to think that perhaps they need a
higher startup current than I can supply. Can anyone confirm this?
Thanks
Rob