That was a switch on the communications ports cover. Required outside
of the US, but in the US they removed the power check switch.
There's a story about Larry Bolhuis, Tom Jarosh, then General Manager of
AS/400 division at an IBM Soundoff session at COMMON. It seems Mr.
Bolhuis was describing the procedures to check a communications
failure. One of the instructions was to open that door and put a wrap
plug on the port and then run diagnostics. Note: at the time if you
opened the communications access cover door, it dropped power to the
entire chassis. Oopsy (as Larry would put it) Mr. Jarosh's reaction
was legendary and had IBMrs diving for the floor under chairs/tables
whatever they could find to get away. Finally Frank Soltis stepped up
and explained why that switch was there (for good reason outside the
US) and why they thought it was important. The next day and
engineering change went out for all US based machines to remove that
switch. Mr. Jarosh did not mess around, and he was a very good General
Manager for the brand. The world lost him in October 2008.
Chief Technical Architect
Agile Technology Architects
On 10/3/2013 12:08 PM, Roberto José Etcheverry Romero wrote:
but i do remember
an old 720 or similar that had switched that turned off the power if
you attempted to remove the BACK cover!