Re: 28V power on Gigabit ethernet board

[Joshua Coombs]

The 28V is generated by the powersupply, and is a constant output, even when 
the supply is 'off'.  There are reports that you can run as low as 5v and 
still be able to boot but you loose ADC and Firewire functionality.  If 
there isn't voltage present on the 28v line, the machine will not boot. 
Interrupting that voltage while the machine is running results in a hard 
lock.

Joshua Coombs
----- Original Message ----- 
From: "Philip Stortz" <[EMAIL PROTECTED]>
To: "G-List" <g-list@mail.maclaunch.com>
Sent: Friday, January 07, 2005 4:49 PM
Subject: Re: 28V power on Gigabit ethernet board


i could be wrong, but i believe that the logic board generates the 28V from 
one of the other
supplies.  if not you'll need a small switching power supply, probably 
running off of the 12V that
puts out 28V.  however, i think i recall a problem with some machines with 
the 28V supply failing
and the firewire ports not working fully afterwards, and i'm pretty sure 
they said the 28V is
generated by the logic board and parts used for the firewire connection. 
do you have the pinout for
the power supply connector that goes to the logic board?  this will tell 
you if it is supposed to
also provide the 28V.  if it isn't made on the board let me know and i can 
probably point you to a
source of appropriate adjustable power supplies to get the 28V you need.

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