Tait TM8100 mobiles Service Manual page 174

Figure 7.3 Power-supply circuitry under the
regulator IC604
CAN FOR
DIGITAL
BOARD
Task 3 —
Check Linear
Regulators
174 Power Supply Fault Finding
This task describes the general procedure for checking any linear regulator.
There are two possible faults: either the regulator has failed and prevents the
radio from powering up, or the regulator voltage is incorrect. (The regulator
IC might or might not have been removed during earlier checks.)
1. Disconnect the 13.8 V supply. Check for continuity and shorts to
ground (if not already done) on the input, output and control line of
the relevant regulator IC. Repair any fault.
2. If the regulator IC has been removed, resolder it in position.
3. Reconnect the 13.8 V supply and press the
powers up or the correct regulator voltage is restored, return to
"Initial Tasks" on page
4. Disconnect the 13.8 V supply. Replace the regulator IC with a spare.
Reconnect the 13.8 V supply and press the
powers up or the correct regulator voltage is restored, go to
Tasks" on page
"Final Tasks" on page
can, including 3V regulator IC603 and 2.5V
CDC BOT
TP601
155. If the repair failed, go to
163. If the repair failed, replace the board and go to
163.
© Tait Electronics Limited November 2007
LO2 BOT CAN
/
key. If the radio
ON OFF
Step 4.
/ key. If the radio
ON OFF
"Final
TM8100/TM8200 Service Manual