Specifications

Q.5.11 TUNE Multimeter
Since the multimeter is a full range meter, the TUNE Multimeter
also provides a second function as a Multimeter for other meter
samples.
Q.5.11.1 Relay Switch
Relay switch K1 is shown with S2 in the Tune Meter Normal
position. Transistor Q2 is cutoff, K1 is de-energized, and the
contacts are in the position drawn.
When the TUNE Meter Multimeter is selected by S2, transistor
Q2 is saturated and K1 is energized. The TUNE Multimeter input
is switched to the output of S7, and the Decimal Point of the
TUNE Multimeter is connected to a timer.
Q.5.11.2 Multimeter Select Switch
S7 is a multi-position switch that is used to select one of 12 inputs
to be measured by the Multimeter. When switched to the EXT
Meter position, any voltage under 70VDC may be connected to
TP11 and measured on the Multimeter.
Q.5.11.3 Decimal Point Timer
To avoid operator confusion, when K1 is energized the Decimal
Point input of U9 is connected to the output of timer U16. The
flashing Decimal Point is an indication that the Tune Multimeter
is in the Multimeter function.
Q.5.12
Power Supplies
DC supply inputs to the board are +22VDC, +8VDC, and -
8VDC, from the low voltage power supply. Each input is fused,
with 2A fuses F1, F2 and F3, and regulated to +15VDC, +5VDC
and -5VDC using regulators U12, U13,and U14. All supplies
have a green Status LED that lights when the regulator is opera-
tional. The output of these regulators are transient protected by
transzorbs.
Q.5.12.1 Regulator Status
In order to be able to have an on-board visual status indication
of regulator operation, it is necessary to have a supply voltage on
the board that does not depend on the regulated supplies. The
+22VDC supply goes to CR8 and CR9 and +8VDC goes through
CR1 to a 5 Volt regulator, U11. This +5 Volts is designated +5VB
and can be measured at TP10.
The +5VB is used as the reference to inputs of comparator U15
through a series voltage divider network. Each supply is con-
nected to a voltage divider and then connected to the other inputs
of U15. With the non-inverting inputs more positive than the
inverting inputs the outputs of U15 are at logic high. This is the
NORMAL condition with no faults.
The +15VDC and -5VDC supplies are used for the multimeter
circuit only.
If one of the regulated supplies fails or drops too low, the
corresponding comparator output will go logic low and illumi-
nate DS17 +15/-5V Supply Fault RED. No additional transmit-
ter action is performed since these are non critical supplies.
The main +5VDC supply comparator output is connected the +
input of a second comparator and DS16. If the supply drops too
low, the comparator output will go logic low and illuminate the
+5V Supply Fault RED. This will cause the output of U15-1 to
go logic low and generate a Supply Fault at J2-9. It is sent to the
Frequency Control Interface board and will generate an RF
MUTE.
Q.6 Troubleshooting
The following information contains general troubleshooting tips
and any precautions if applicable.
Faults on this board may be classified into:
a. Frequency Control
b. Metering
c. Power Supplies
Q.6.1
Frequency Control
a. If frequency related faults occur, such as Frequency Syn-
thesizer, go to the Frequency Change mode:
b. Select F1 on the front panel. Check the logic level of all
BCD inputs at J3 and all 6 Bit Binary outputs at J1. They
should match the data shown in the chart as described
above.
c. Select F2 on the front panel. Check the logic level of all
BCD inputs at J3 and all 6 Bit Binary outputs at J1. They
should match the data shown in the chart as described
above.
1. If the BCD inputs are incorrect, check 3F Controller
switches.
2. If the 6 Bit Binary output is incorrect, replace the
BAND ENC PAL.
Q.6.2
Metering
a. If both Multimeters fail to turn on, check the +5VA supply.
1. If no +5VA supply, check Q1, U4, and the STATUS
PAL.
b. If the Multimeter readings do not switch between Refer-
ence and Position voltages:
c. Checkthe U8 switch control voltage,it should show a logic
low for Position, and a logic high for Reference voltage.
1. If the voltages are correct, suspect U8.
2. If the voltages are not correct, suspect the STATUS
PAL.
d. If the Multimeters are operational, but give the wrong
measurements:
1. Check the +2.00VDC, +5VDC, and -5VDC supplies.
2. Use the Lamp Test to test all LED display segments.
Q.6.3
Power Supply
a. If DS17 is illuminated RED:
b. Use the Multimeter to measure the +15VDC and -5VDC
power supplies.
c. If either supply has been reduced to less then 80% of
normal:
1. Check the input fuse and replace if necessary.
888-2339-002 Q-5
WARNING: Disconnect primary power prior to servicing.