Testing H745 Regulators

[Mattis Lind]

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
>
>