How to lock your EEprom

Parts Needed

  1. Switch, Single Pole Double Throw (SPDT)
  2. Resistor, 1K-Ohm ¼ Watt
  3. Wire, Wire Wrap type wire preferred

Tools Needed

  1. Soldering Iron, (NOT a soldering GUN)
  2. Pencil type 30-45 Watts
  3. Solder, Rosin Core, .062" diameter or smaller,
  4. 60/40 Tin-Lead mix Soldering Aids,
  5. Pick type tool to lift pin

Switch wiring diagram and internal mechanical view

EEPROM Pin Out Diagram:

Referring to the graphic below, the "Asterisk" denotes pin-1 on all DIP (Dual Inline Package) styled chips. Some chips may have a "dimple" while others may only have the "U". The pin to the LEFT of the "U" IS pin-1, in case your EEPROM chip does not have the "dimple".

The pin out on the EEPROM is as follows: 

1--|*-U-|--8 
2--|-----|--7 
3--|-----|--6 
4--|-----|--5

Wiring Procedure

  1. Drill a hole in the back of the IRD frame, and mount the SPDT switch so that the legs/pins on the switch are lining up in a vertical manner.

  2. Locate the serial EEPROM. This IC is an 8-pin chip usually surface mounted, and most are a Microchip 24LC16B.

  3. Lift pin-7. To do so heat the pad and use a dental pick tool to gently lift the pin from the copper land.

  4. Solder a wire from the lifted pin-7 on the IC to the center pin of a SPDT type switch.

  5. Solder a wire from pin-4 (Vss or Ground) to the bottom pole of the switch (Do not use the pad from pin-7 since the space between the lifted pin-7 and the pad is so small, that doing so can cause short).

  6. Solder a 1K-Ohm ¼ Watt resistor to the remaining leg on the switch.

  7. Lastly solder a wire from pin-8 of the EEPROM to the free leg on the 1K Ohm 1/4 Watt resistor.

    With this modification controlling the EEPROM is now that much easier.

    Switch Settings:

    • To UNLOCK the EEPROM, flip the switch lever so that it points UP.
    • To LOCK the EEPROM flip the switch lever so that it points DOWN.

    Switch lever

    EEPROM wiring diagram

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