AR 10027190, Operating And Service Manual

Page: 28 / 62

Models 200T18G26z5A/200T26z5G40A
Rev – 18
3.7 FOLDBACK OPERATION
Forward FOLDBACK and reverse FOLDBACK circuits are used on both the 18G26z5 and 26z5G40. In the
event the output power exceeds or the reflected power exceed factory limits a fold back circuit will active,
and control the solid-state amplifier attenuation to ensure the output power is kept to fixed limit.
Forward Fold back
The forward FOLDBACK protection circuit will activate if RF output power exceed 250W. The TWT
display screen will flash “FOLDBAK ACTIVE” warning. The cover plate on the front panel allows access to
the forward fold back circuit. The limits are set at the factory and do not require adjustments.
CAUTION:
Do not adjust 20-turn pot R11; its function is to set the Forward foldback
VSWR level, and it is calibrated at the factory.
Reverse Fold back
The reverse FOLDBACK protection circuit will active if the reflected power exceeds 20W. The TWT
display screen will flash “FOLDBAK ACTIVE” warning. The revise fold back is located internally to the
machine on A32363-000 VSWR & FOLDBACK board assembly.
3.8 REMOTE IEEE-488 OPERATION
The TWTA is provided with an IEEE-488 interface that permits remote emulation of OPERATE,
STANDBY, and RESET push-buttons as well as access to parameter measurements, system faults, gain
adjustment and control unit status. The following tables summarize the commands and the return codes.
Table 3-3. Catalog of IEEE-488 Commands
Command Function Units Response format
RDSTAT Returns status code of processing of previous command
(see Table 3-4) STATUS=[ ]
RDFLT Returns system fault code (see Table 3-5) flt=[ ]
OPERATE; Emulates OPERATE push-button
STANDBY; Emulate STANDBY push-button
POWER:OFF; Emulate STANDBY push-button
SYSTEM:ON; Emulates pressing the System ON button from System OFF
(Exit Sleep Mode)
SYSTEM:OFF; Emulates pressing the Power Save button. (Enter Sleep
Mode)
RESET; Emulates RESET softkey
RDS/N Returns serial number s/n=[ ]
RDCONHR Returns console hours ConHr=[ ]
RDRFHR Returns RF hours RfHr=[ ]
RDEK1 Returns cathode voltage, HPA1 KV Ek=[ ]
RDEK2 Returns cathode voltage, HPA2 KV Ek=[ ]
RDEB1 Returns collector voltage, HPA1 KV Eb=[ ]
RDEB2 Returns collector voltage, HPA2 KV Eb=[ ]
RDEG1 Return grid voltage, HPA1 V Eg=[ ]
RDEG2 Return grid voltage, HPA2 V Eg=[ ]