
PART XII.                   HOW THE ESN IS REPLACED

        It takes some electronics skill to pull or unsolder the ESN.  If you
are sketchy about messing around with your phone, I suggest practicing on 
something else first, like an old calculator or something.  It is also a
good idea to use the proper tools (A very small soldering tip,chip pullers,
It is imperative NOT to touch any of the surrounding connections, soldering
joints, or chips.  The job MUST be done right the very first time.  After
that it is not so important, because after the first time you should have the
ESN information stored safely to disk.  The only dangers remaining are
physically damaging the chip.  (Note: There are devices that wipe PROMs
clean in the event of programming errors).

        When removing the ESN, try to follow these 5 steps:

A. Remove the PC board containing the ESN from the entire phone unit.  The
boards are usually screwed in with Phillips heads.  This will insure 
against damage to the rest of the unit.

B.  Ascertain the correct chip.  Find the letters on the chip, and check it
against the letters from the IDENTIFYING THE ESN section. Refer to the .Gif
file included if necessary.

C. It is a good idea to draw a sketch to help you remember which way the chip
went in.  You may laugh, but do it anyway.

D. Carefully remove the chip.  Take your time and use the proper tools.

E.  Solder in a zero insertion force (ZIF) replacement, so that replacement
chip can be changed easily.

        After the ZIF socket has been successfully soldered in, reinsert the
ESN and attempt to make a phone call (Be sure the NAM is programmed
correctly). If it doesn't, check the leads on the ZIF to insure that you
have soldered them correctly.  After that, insert your ESN into your PROM
reader and make sure it provides some sort of reading.  You should use the
search mode to look for the manufacturers serial number.
(see MANUFACTURER'S ESN CODE LISTING) to identify the address on the PROM
where to reprogram the ESN.

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