PDP-11/34A / BA11-K PSU

From: Jochen Kunz <jkunz_at_unixag-kl.fh-kl.de>
Date: Tue May 27 17:19:01 2003

On 2003.05.26 23:47 Tony Duell wrote:

> There are several good references on SMPSU design
I should feed google... ;-)

> (the section in 'The Art of
> Electronics' 2nd edition is a good staring point),
Unfortunately I don't own this book. When I tried to order it from .de,
the cost was prohibitive.

> and these DEC PSU
> bricks are a pretty standard step-down regualtor circuit.
Well, it looks like the H7441 has some funky design tricks.

> The only unconvention feature is that the controller is
> a 723 chip, not a special SMPSU chip.
The H745 has a 723, the H7441 has two OPAs and two NE555. The H745 looks
quite simple and I think I understand what the different parts do, but
the H7441??? One OPA seams to do some over current protection, one the
voltage regulation. So the NE555 are doing the ON / OFF timing??? Have
to dig deeper into that...

Unfortunately it doesn't seam as simple as the SGI Indigo2 PSU repair I
did today. I had a close look at the PCBs of the PSU and saw
electrolyte... The machine seams to run stable again, now that I
replaced the electrolyte capacitor in question. :-)
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
Received on Tue May 27 2003 - 17:19:01 BST

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