/34 & ba11-k regulator allocation?

Don North ak6dn at mindspring.com
Fri Oct 13 12:47:06 CDT 2006

John A. Dundas III wrote:
> Jay,
> At 10:07 AM -0500 10/13/06, Jay West wrote:
>> Exactly what regulators are required as a minimum for a /34 that is 
>> just a dd11-pk with no expansion? Assume just a processor, one memory 
>> board, RL11 controller, one DL11W... nothing heavy.
> A timely question as several of us seem to be working on this model 
> currently.  [Thanks to Julian, Tim, Don, Al, Henk, and all others that 
> have contributed to my own success...]  Others will no doubt correct 
> my errors but...
> I believe for the configuration above one H744 (position 2) IS 
> required.  I believe a H745 (position 1) IS also required.  A second 
> H744 (position 3) does NOT appear to be required based on your 
> configuration above.  I'm not clear whether or not a H754 is required 
> in position 4.  My take is that regulator is used primarily for core 
> memory (+20, -5), though I could be wrong.
> Note that there are other regulators that can be used in place of the 
> H744.

John is exactly correct in his analysis WRT the H744 +5V in slot 2 and 
H745 -15V in slot 1. The second H744 in slot 3 is not needed unless you 
have expansion backplanes. The H754 +20V/-5V in slot 4 is only required 
for core memory. Later generation BA11-K series boxes allowed for a 
battery backup regulator that would go into slot 4 (for MOS memory) in 
place of the core voltage regulator.

The H744 is a +5V/25A module; the later generation H7441 is +5V/32A and 
is plug compatible. Technically there is an upgraded power distribution 
board (54-something-YA) that is supposed to be swapped in when the 
H7441s replace the H744s (-YA has beefier wiring for +5V distribution) 
but this is only an issue if you are pushing the limit on an H7441.

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