AMX TXC16 Plus Specifications download pdf (Page 188)

SG-2000 MANUAL 181

The SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA

Verify that V2 - V1 = 4.5 VDC ± 0.5 VDC.

23.2.8 Temperature Sensor Check

The Temperature Sensor is built around IC1 on the LPA board and functions as

follows:

At room temperature, the voltages on pins 1, 2 and 3 of IC1 are as follows:

IC1 pin 1 = 3.6 VDC

IC1 pin 2 = 0.05 VDC

IC1 pin 3 = 0.92 VDC

When the temperature of the heatsink reaches;

+55° C ±5° C (the low temperature trigger) the voltage on pin 2 of IC1 is = the

voltage on pin 3. This will cause the voltage on pin 1 of IC1 to drop to near 0,

which will be sensed by the Main CPU board. Data will be sent 1) to the Head

to flash the TEMP indicator, 2) to IC4 to pull pin 14 low (IC1 pin 2 will again go

lower than pin 3 and pin 1 will go higher) and 3) to IC4 to pull pin 13 low to

start the fan running.

+70° ±5° C (high temperature trigger) 1) the fan will continue running, 2) IC4

pin 15 will go low which will switch the radio to Low Power transmit mode

and 3) LO PWR will be displayed on the Head and the TEMP indicator keeps

flashing.

On LPA Test Box, SW4 is a 3 position switch

Middle = L4 will stop lighting when temperature reaches low temp trigger

point

Right = L4 will stop lighting when temperature reaches high temp trigger

point.

Left = Simulation of low temp trigger point

In normal LPA testing on the bench, the temperature of the heatsink at

thermister R75 is not allowed to reach trigger points. LPA Test Box simulates

the increase of resistance with temperature and reaching the low temperature

trigger points when SW4 is in the left position.

On LPA Test Box, turn SW3 to RCV position.

Flip SW4 through the 3 positions. If the temperature is less than 55° C ±5° C, L4

will stop lighting only in the Left position.

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AMX TXC16 Plus Specifications Page 188