11/34a power supply/regulator question

[Tony Duell]

> After looking at the prints and checking a few voltages, I find I have
> no +5.  Reviewing the recent thread and looking closer at the prints, it
> seems that I am missing two H7441s.  (It does have a H754 and H745, with
> the 54-10864-YA [Rev. L] distribution board.)  Is that correct?  It
> needs (one or) two H744 or H7441 (in my case) in order to operate?

Yes, I believe so. The only 5V source is from those regulator blocks, and 
of course most of the logic runs off a 5V supply. AFAIK there are 3 types 
of regulator you can use, the H744 (rated at 25A), the H7440 (also 25A, 
but a revised design) and the H7441 (32A). Apart from the rating, 
they're compatible, so if 25A is unough you could use any of them. They 
also don't both need to be the same type.

I can't remmeber how the 5V line is 'split' Certainly the complete CPU 
backplane runs off one regulator, the leftmost 2 'system unit' postions 
run off the other. It's the middle 'system unit that I can't remmber, I 
think it's off the regulator that runs the leftmost 2 positions too. In 
other words one block runs the CPU backplane, the other all the expansion 
backplanes. But I would have to check the prints to be sure.

-tony