Testing H745 Regulators

Rob Jarratt robert.jarratt at ntlworld.com
Wed Jan 26 17:41:55 CST 2022

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?





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