26 Jan
2022
26 Jan
'22
5:12 p.m.
Get yourself a largeish 24V transformer, I use an old 8A Stancor:
http://www.glitchwrks.com/images/dec/pdp1110_psu_repair/5411086_under_test.…
The AC input can be between 20-30V so it's not critical. Plenty of other "control
transformer" type units would do fine.
You shouldn't need a lot of current on the 15V rail.
Thanks,
Jonathan
------- Original Message -------
On Wednesday, January 26th, 2022 at 19:22, Rob Jarratt via cctalk <cctalk at
classiccmp.org> wrote:
-----Original
Message-----
From: W2HX w2hx at w2hx.com
Sent: 27 January 2022 00:11
To: rob at jarratt.me.uk; Rob Jarratt robert.jarratt at ntlworld.com; General
Discussion: On-Topic and Off-Topic Posts cctalk at classiccmp.org
Subject: RE: Testing H745 Regulators
Any chance you have a second supply you can parallel with the one you're
using? Some bench supplies are dual supplies and have a parallel mode so
you can benefit from both sides of the supply and they can track the same
voltage. Or just put two supplies in parallel with the same voltage set on
both
It is already a twin PSU, I am using one half to power the AC input and the
other half to power the +15V input.
I do have a separate bench PSU I could use for the +15V and twin up the
actual twin PSU, so I might try that next.
73 Eugene W2HX
Subscribe to my Youtube Channel: https://www.youtube.com/c/w2hx-
channel/videos
-----Original Message-----
From: cctalk cctalk-bounces at classiccmp.org On Behalf Of Rob Jarratt via
cctalk
Sent: Wednesday, January 26, 2022 6:42 PM
To: General Discussion: On-Topic and Off-Topic Posts
cctalk at classiccmp.org
Subject: Testing H745 Regulators
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