Power Supply Faulty - Tait TM8235 Service Manual

14.2

Power Supply Faulty

Figure 14.1 Circuit diagram of the power supply circuitry
L1
13V8
2
J103
6
Control-
Head
Connector
408 Fault Finding of Control Head with Graphical Display
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.
2
4
3
Q201
2
1
R202
3
6
8
For all faults, check that the supply voltages are correct:
1. Check the 3.3V supply voltage between E202 and C210.
E202/C210: 3.3V
If the signal is correct, continue with
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
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
U1 pin 8: 13.8V (V
If the signal is correct, continue with
Note
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.
8
L201
VCC
1
OUT
SYNC
6
U1
COMP
VREF
INH 5
FB
GND
7 GND
4
IN OUT
U203
5
EN RST
GND
3 6
R204
3V3
DNI
4
1 K1 AA
MR RST
7
D203
PFI U202 PFO
2 K2 AA
WDI WDI
GND
D203
5
Step
Step
=9.7V...17.2V)
s
=9.7V...17.2V)
s
Step
3V3
E202
3V3
+
1V5
E203
1V5
FPGA
MR
PWR WDT
3V3
PWR RESET
4.
2.
3.
TM8100/TM8200 Service Manual
© Tait Electronics Limited June 2006