Open the blue case and power off the unit.

In the lid is a hinged aluminum plate with the "Intel" printed
circuit board visible. There are three philips screws holding
down the plate along the top edge.

Remove the three screws along the top edge.

Swing the PCB mounting plate forward on hinges.

The board on the back of the PCB mounting plate now exposed
is the A/D board with the EPROM to be replaced.

Remove the labeled EPROM from the socket carefully. (Slip
a small flat screwdriver under the IC at the end and pry
up gently remembering that there is a socket, which does not
come out, below the bottom of the EPROM IC)

Note the IDS serial # and date on the label of the removed
EPROM IC.

Install the new replacement EPROM in the socket with caution
and noting that all pins have inserted into holes and that the
chip orientation is correct. One end of the EPROM has a curved
notch and this notch should line up with the chip outline
printed on the board. This notch indicates the pin 1 end and
is facing down in the photo. Look closely as possible that all
pins entered the socket holes and that none have folded under.
If they have, remove the EPROM, straighten the pin and try again.
This will only work for several straightenings before the pin
breaks off, so be carefull the first time. When it appears that
all pins are aligned and the chip is in the right orientation,
push down firmly on the EPROM IC to seat the pins.

Fold back the PCB mounting plate and replace the screws.

Power up the unit and check data stream for julian day.

Done.