OEM controllers (was Hijacking oem hardware)

[Tom Cloud]

>
>> yeah, and if you wanted to "clear" the board in a hurry, you'd
>> just take it to a belt sander -- and be careful not to take off
>> any traces
>> 
>>  ... do any of the multi-layer PCB's have any internal parts ??
>> 
>> that'd really muck up my idea (well, caps probably wouldn't mess
>> up the wiring, but anything else could)
>
>
>If all components were removed, about how many contact points
>are on the board...as in, how many connections are there between
>the board and its components? If it is a reasonable number, 
>the ciruits could be learned via test equipment. I'd have to
>check on the value of "reasonable number". If you've got a 7 layer
>board, I'm guessing it's got bunches of components, though.
>
>-greg

there'll be thousands of contacts on a typical ecm board, but
I'm not deterred by the factorial thingie ... I'm probably
nutsoid, but here's what I would do

 - get a majic marker or some fingernail polish - to mark where
you've already been

 - get a brass brush with a metal handle to make a "sweep" probe

 - use your "beeper" continuity checker or a light bulb and a
battery

 - now, you have to have some way of identifying each component
connection (circuit node) on the board (don't care about vias -- though
they probably won't be distinguishable from "real" connections)

 - draw some grid lines on the board and label them, like on a
map

 - write a reference designator for all IC's and put a dot by pin 1

(I gotta confess, I haven't figured out how to identify all the
connecting points .....  any suggestions ?? )

 - make the wire map with a "From" and a "To" column.  The "From"
needs to be only wide enough to take one x-y coordinate or IC-#
coordinate.  The "To" column should be as wide as possible to accomodate
all the daisy-chain connections

 - start in one corner. put the probe on the first point and "wipe"
the entire board, taking care not to miss any of it, with the brass
brush probe.  Then the beeper goes off, take an alternate, pointed
probe and fine which of the connections the brush touched is the
active one

 - fill in the wire map with each "To" location

 - (optional) mark each "To" spot so you won't check it again

Then, when you're done, you've got to match each of your coordinate
points with a component so you can draw the schematic

None of this is very pretty, but it seems a reasonable alternative
to X-rays and decapitation  ;-)

Tom Cloud

      Insanity is hereditary, you get it from your kids!