IF/Converter Module Interface (PC1J6)
Jack – Pin #
Function
2
6
11
J8 – 10
OUTPUT AGC CONTROL: This voltage is applied to switch PC1S2 which
determines if the IF output AGC is active (high) or fixed (low). With the
OPERATE/SWEEP switch S1 in the SWEEP position, the ground at U3C will
cause the output U4C-8 to go low, switching PC1S2 to place a ground on
PC1U18. This low forces PIN diodes PC1CR9/CR10 to stabilize at the center of
their attenuation range (
3dB). Releasing the front panel AGC/MANUAL switch
PC3S2 will deactivate the output AGC by supplying a ground to J10-9 via
PC3J1-9. The low at U4A-2 will cause the outputs of U4D and U4C to go low,
again inhibiting the AGC. In the TTU500FA, a power supply or transistor failure
occurring in the 500W Power Amplifier drawer (A3) will furnish a low at J4-1 from
A5PC1J3-1. The low at U4A-1 will drive the outputs of U4D and U4C toward
ground with the same affect. If the operator wishes to remotely deactivate the
transmitter’s output AGC, a ground can be applied to pin 7 of REMOTE jack
A8J1 on the Video/Audio/Remote Panel at the rear of the transmitter cabinet.
This ground will be fed to U4D-12 from A5PC1J5-6 to J5-6 and to U4D, pushing
U4C-8 low. Whether the output of AND gate U4C is at a logic high or low, that
signal is also sent to pin 18 of J10 through resistor R23 and on to front panel
AGC ACTIVE LED P3DS6. If the voltage is high, transistor PC3Q6 will be
forward biased causing the LED to turn on, indicating the output AGC is active.
If the voltage at PC3J1-18 is low, PC3Q6 will not conduct and PC3DS6 will not
illuminate indicating an inactive output AGC.
2W UHF Amplifier Module Interface (A1J3)
Jack – Pin #
Function
J6 – 1
+28V: From J3-6 to A1J3-1
J6 – 2
+15V: From J3-5 to A1J3-2
J6 – 3
STATUS: This high or low voltage originates from A1J3 pin 3 to indicate the
status of the transistors within the 2W UHF Amplifier module. A high indicates
that the devices are operating properly creating highs from U3A and U3B while
lighting AMPLIFIER STATUS LED PC3DS1 via R8, J10-26 and PC3J1-26. If a
transistor fails within A1, the STATUS line will go low sending the outputs U3A-3,
U3B-6 and U2B-6 low. A low will emanate from U8A and pass through J10-21,
PC3J1-21, LEVEL ADJUST PC3R16, PC3J1-23, J10-23, J8-7, PC1J6-7 and
PC1U9-5, increasing the IF attenuation of PIN diodes PC1CR7/CR8 and signif-
icantly reducing the output power of the Exciter and, therefore, the transmitter.
The low at the output of U3A will also extinguish the front panel AMPLIFIER
STATUS LED PC3DS1 via J26 and PC3J1-26.
J6 – 4
GAIN ADJUST VOLTAGE: This 0 to 12V potential is delivered to A1J3-4 to
control the gain of the 2W Amplifier module through manipulation of hybrid
attenuator A1HY1/CR-1/CR2. The voltage is delivered by variable voltage regu-
lator U12 with AMPLIFIER GAIN ADJUST potentiometer R7 controlling its out-
put. The voltage to R7 is supplied by
5V regulator U11 fed from the
15V
supply.
J6 – 9
GND: Ground to A1J3-9