KeyPad
Version 1.0
SCP SCIENCE
33
A/D CONVERSION PROBLEM
If the section 5 has been fully investigated and
the system does not provide the right temperature
readings, verify the analog supply and the analog ref-
erence voltage of the microcontroller U6.
• With the negative lead of a multimeter on the via
connected to pad C25-1 and its possible lead on
the via connected to pd C25-2, you should read
5Vdc.
• With the negative lead of a multimeter on the via
connected to pad C25-1 and its positive lead on
the via connected to pin U6-27, you should read
5Vdc.
If those values are less than 4.8V, replace the
KeyPad PCB.
CPU UNSTABLE
If CPU is resetting by itself, check pin 9 of U6.
WIth the negative lead of a multimeter on pin 3 of J1
and its positive lead on pin 1 of J1, you should read
a steady voltage value of at least 3.7 Vdc. If not, re-
place the KeyPad PCB.
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