Rf Carrier Detect - GE Medical Systems Corometrics 340 Service Manual

RF Carrier Detect

Revision A
Calibration: Receiver Calibration
6. Refer to Table 5-4. Confirm each tone decoder output locks. The
output will go to a logic low state when a 50 mVRMS sine wave of
proper frequency is applied to each input at pin 3 of each IC.
Input
C Reference
U26-3
U28-3
U14-3
U21-3
7. Ground TP18. Confirm TP30 goes to a low with the presence of the
20 Hz mode tone.
8. Remove the 20 Hz tone. Confirm TP31 goes to a low with presence of
2600Hz subcarrier only, with 1.0 Vp-p at TP 45.
DC
VOLTS
DC SUPPLY
1. Disconnect the UHF receiver module at J6. Connect the positive lead
of a 0 to +5 Vdc adjustable voltage source to J6 pin 3. Connect the
negative lead of the variable voltage source to J6 pin 5. Set R1 fully
clockwise (wiper at +5 Vdc). Set the variable voltage source to +2.0
Vdc. Observe the following: the signal indicator is off, and a high
signal is on J4 pin 3. Adjust R1 counter-clockwise until TP1 goes
low. Observe that the signal indicator flashes at approximately 1-
second intervals. Increase the voltage from the variable voltage
source until the signal indicator stops flashing and remains
illuminated. Confirm the voltage source is at +3.0 ± 0.45 Vdc.
127( R1 may need to be readjusted with the UHF receiver module
reconnected to J6.
2. Remove the voltage source while observing TP1. TP1 should go high
between 0.2 and 0.8 seconds after the voltage source is removed.
3. With TP1 low, confirm the weak battery indicator signal located on
J4, pin 5 flashes at approximately 1-second intervals with TP12 and
TP7 jumpered to ground. Confirm the indicator illuminates
continuously with only TP1 and TP12 low, and is off if TP1 or TP12 is
high.
Model 340 Telemetry System
2006920-001
Table 5-4. Tone Decoder Output Locks
Input
Center Frequency and Voltage
10 Hz at 50 mVRMS
20 Hz at 50 mVRMS
40 Hz at 50 mVRMS
80 Hz at 50 mVRMS
Output
Test Point
TP7
TP47
TP48
TP12
5-9