pass 2.1 changes


              ENGINEERING CHANGES TO THE PASS 2.1 LONGTRAIL BOARD


LAST REVISION :    3/31/97
                   4/01/97

Notes and workarounds
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1) The design was changed to populate *k of NVRAM instead of 32K.  A change
   in the OF is required because of this.

2) The first 5 borads were built with GG-3 and Hydra-3. The correct BOM is
   GG-4 and Hydra-4.

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                           ECs

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EC#1      MISSING PULLUPS AT GPIO       3/31/97

We failed to put pullup resistors on the outputs of GPIO 13,14.  As a result
when power is turnd off these outputs float and may cause U36 to set.  This
turns the power back on.  See page 27.  The pullups must be to Vaux.


CHANGE

   Add 10k pullup from U30.12 to U30.14           pull GPIO 13 to vaux

   Add 10k pullup from U36.4 to U36.14            pull GPIO 14 to vaux

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EC #2   VRM OUTPUTS INCORRECT    3/31/97

Pins were assigned in the CPU socket to accomodate future PGAs which plan
to directly control the VRM.  It turns out that one of the pins assigned
is a ground on present PGAs.  This causes the VRM input to always have a
stuck bit.  Page 5 .  A temporary solution is to remove the stuck bit
by cutting the trace to the PGA.

CHANGE:

  On the backside, cut the trace coming from M4.C02.  Make the cut so that
  only M4.C02 is removed from the net.


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EC # 3      CORRECT POOR AUDIO QUALITY

We changed the audio chip frequency source to a crystal in pass 2.1 to save
money.  In doing so, we retuned the ground for the caps at the crystal to
digital ground.  Mistake.   These need to return to a clean audio gnd.
See page  32.


CHANGE

Locate the fat wire on the back side running between C42.2 and C357.2.

Cut this wire (GND net) near the C357.2 end

Add a wire from C144.2 to C105.2  (GNDA net).

Check to see that C144.2 and C42.2 now connect to GNDA net.

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