The switch positions for the meter are as follows:
•
OFF
(1)
•
B +8V IN (2)
•
B B+ OUT (3)
•
B -8V IN (4)
•
B B- OUT (5)
•
+5V IN (6)
•
+5V OUT (7)
•
-5V OUT (8)
•
SPARE
(9)
•
B- REF (10)
•
B- DRIVE (11)
•
A +5V IN (12)
•
A B-
(13)
•
A -8V IN (14)
•
A B+ OUT (15)
•
A +8V IN (16)
M.3
Troubleshooting
NOTE
Prior to starting a troubleshooting procedure check all switches,
power cord connections, connecting cables, and power fuses.
A fault on the DC Regulator will register as either a B+ or B-
fault on the ColorStat™ panel. To determine which circuit on the
DC Regulator is registering as a B+ or a B- fault, P1 should be
moved to the TEST position. This will enable the individual fault
indicators on the DC Regulator.
CAUTION
DO NOT LEAVE P1 IN THE TEST POSITION FOR EXTENDED
PERIODS OF TIME DUE TO LACK OF COOLING FOR THE REGU-
LATOR PASS TRANSISTORS.
M.3.1
Symptom: B+ Fault
An ambient temperature greater than 70 degrees C or any fault
in a DC Regulator positive supply will result in a B+ fault
indication on the ColorStat™ panel. To isolate a B+ Fault:
a. Move Jumper P1 to the TEST position.
b. Note which LED is illuminated
c. Read LCD Multimeter reference voltage
Once the fault is isolated to an individual circuit, troubleshoot
possible causes.
M.3.1.1
+22V Fault
This would indicate an open fuse F1 or F4 on the DC Regulator,
depending on the particular fault indicated. The +22 VDC is
distributed to the Modulation Encoder (A37) for the Cable
Interlock circuitry. Any IC or component associated with the
+22 VDC Interlock circuitry should be inspected for a short
circuit or evidence of discoloration due to overheating.
M.3.1.2
MOD ENC +5V Fault
The +5 VDC is derived from the B+ voltage on the Modulation
Encoder (A37) and is used to power various IC’s. A short circuit
in any IC on the + 5VDC line will result in an open fuse F1.
M.3.1.3
B+ REG Fault
Disconnect primary power from the transmitter before checking
components. With the supply’s fuse removed, check from emitter
to collector of the pass transistor, using an ohmmeter on a low
Ohms range (recall that there is a rectifier diode across the pass
transistor). If you read a short, remove the pass transistor to check
the diode and transistor separately. Diode failure is unlikely,
unless a reverse voltage has been accidentally applied at the
regulator input.
If the pass transistor and protection diode check good, swap the
suspected defective regulator IC with a known good IC.
If the regulator IC is not the problem, an ohmmeter should be
used to locate a shorted load or defective IC.
M.3.2
Symptom: B- Fault
The troubleshooting procedure for the B- regulator circuit is the
same for the B+ regulator. If the basic regulator circuit appears
to be operational, check the following:
M.3.2.1
Modulated B- Supply Controls Not Adjusted Prop-
erly
Refer to the Tuning/Frequency Change Procedure in SECTION
V, Maintenance, for adjustment procedures.
M.3.2.2
No -(Audio + DC) Signal From the Analog to Digital
Converter
With program audio applied to the transmitter, check the B- Drive
signal at TP14 for a -(Audio + DC) signal.
Section M - DC Regulator (A30)
888-2297-002
M-5
WARNING: Disconnect primary power prior to servicing.
