Ericsson R250s PRO Troubleshooting Instructions page 31

The functional schema is shown in the figure below.
Make sure there is voltage (3.2V) at the pads of the keys.
Note that the "No" key has 4.8V.
If the voltage is missing at an entire row of keys, measure the voltage at the corresponding pin
of D600
•
If the voltage is correct at D600 there is a foil damage, send the unit on according to the
local company directives.
•
If the voltage is missing there too, replace D600.
If VDIG is missing at any row of keys, for instance key 2 and 3, but at key 1 there is voltage,
there is a foil damage, send the unit on according to the local company directives. This can be
verified by measuring the resistance from a functional key to one that is not functional (~0
ohms). If the resistance is incorrect there is a foil damage.
If an entire column is non-functional, measure the resistance from the pad to the corresponding
pin of D600.
If there is a foil damage, send the unit on according to the local company directives.
If only part of a column is non-functional, measure the resistance from a functional keypad in
that column to a non-functional to verify a foil damage.
4/00021-2/FEA 209 544/18 D
Standard Trouble Shooting Instructions
31(35)