Tait TM8100 mobiles, Service Manual

Page: 427 / 620

TM8100/TM8200 Service Manual Fault Finding of Control Head with Graphical Display 427
© Tait Electronics Limited November 2007
If the signal is not correct, check the 13.8V supply voltage from the
radio body. Return to
Step 1 .
3. Check the inhibit signal at pin 3 of U1.
If the signal is above 2.2V, visually inspect the components D1, R16,
R17, R208, and Q201 for open or shorted contacts. Replace if nec-
essary. Return to
Step 1 .
If the signal is low, replace U1. Return to Step 1 .
4. Check the 1.5V supply voltage at pin 4 of U203.
If the signal is correct, continue with Step 6 .
If the signal is not correct, continue with Step 5 .
5. Check E203 for continuity.
If E203 is correct, continue with Step 6
If E203 is faulty, replace E203 and return to Step 4 .
6. U202 detects a possible power failure and generates an output signal
on pin 7. Check whether this signal is low.
If pin 4 measures 3.3V and pin 7 is low, replace U202.
If pin 4 measures 3.3V and pin 7 is high, replace U203.
U1 pin 3: high: >2.2V, low: < 0.7V
D1: V
s
– 5.1V
U203 pin 4: 1.5V
E203: 1.5V
U202 pin 4: 3.3V
U202 pin 7: 3.3V
Figure 14.2 PCB layout of the power supply circuitry
top side
Junction of C210 and E202