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. *****************************************************************************