Back-to-back zener diodes CR3 and CR4 should indicate a low
leakage current in either direction; if one of the diodes is shorted,
they will look like a single diode with an ohmmeter check or
“diode test” function on a digital multimeter. Note that CR3 and
CR4 are each in parallel with a 10-Ohm resistor and low resis-
tance toroidal transformer winding, so in-circuit checks are not
possible. One end will have to be removed from the circuit to
test.
B.3.1.2
Possible Cause: Coaxial Cable or Connector Fault
With all power removed from the transmitter, you can remove P4
from the Oscillator Board and check for a 50-Ohm resistance into
P4-8 and 9; this indicates that the coaxial cable and connectors
are good.
B.3.2
Symptom: Buffer Amplifier LED on Color-
Stat™ panel is Red, transmitter will operate.
If the transmitter will operate, but the ColorStat™ panel LED is
red, there is a detector failure on the Driver Combiner/Mother-
board or a fault circuit failure on the LED Board. Refer to
SECTION D, Driver Combiner/Motherboard and SECTION Q,
LED Board, for troubleshooting information.
DX-25U
B-2
888-2297-002
WARNING: Disconnect primary power prior to servicing.
