Power Supply Faulty; Circuit Diagram Of The Power Supply Circuitry - Tait TM9100 Service Manual

14.2

Power Supply Faulty

A 3.3V regulator (U1) converts the switched 13.8V supply from the radio
body to 3.3V. A 1.5V regulator (U203) converts the 3.3V to 1.5V.
A power-sense module (U202) verifies the outputs of the voltage regulators
and—in the case of a fault—creates a power reset signal which is processed
by the FPGA. If the start-up of the control head fails, the radio body reduces
the switched 13.8V supply shortly after power is supplied.
Figure 14.1

Circuit diagram of the power supply circuitry

L1
13V8
2
J103
6
Control-
Head
Connector
For all faults, check that the supply voltages are correct:
1.
2.
Note
400 Fault Finding of Control Head
8
VCC
OUT
2
SYNC
4
U1
COMP
VREF
3
INH
FB
GND
7
GND
Q201
2
IN OUT
U203
1
EN RST
GND
3 6
R202
3V3
4
3
MR RST
6
PFI U202 PFO
8
WDI WDI
GND
5
Check the 3.3V supply voltage between E202 and C210.
E202/C210: 3.3V
If the signal is correct, continue with step 4.
If the signal is not correct, visually inspect the components E202,
D201, L201, R205, and R206 for open or shorted contacts.
Replace if necessary. Continue with step 2.
Check the 13.8V supply voltage (9.7V to 17.2V) between pin 2 of
the control-head connector J103 and pin 8 of U1.
J103 pin 2: 13.8V (V =9.7V...17.2V)
s
U1 pin 8: 13.8V (V =9.7V...17.2V)
s
If the signal is correct, continue with step 3.
A fault in the control head can cause the radio body to reduce the
switched 13.8V supply shortly after power is supplied. In this case,
the control head must be supplied directly through pin 2 of con-
nector J103.
L201
E202
1
6
5
+
E203
4
5
R204
3V3
DNI
1 K1 AA PWR RESET
7
D203
2 K2 AA
D203
© Tait Electronics Limited August 2005
3V3
3V3
1V5
1V5
FPGA
MR
PWR WDT
TM9100 Service Manual