Reference: Alpha 87A Fault Codes

Code Type Description
1 Soft Receive PIN back bias voltage not at minimum required level with key down and no RF drive.
2 Hard Five volt supply voltage too low.
3 Hard Five volt supply voltage too high.
5 Hard Plate voltage abnormally low.
6 Hard Plate voltage abnormally high.
7 Soft Cathode and/or power PIN diode back bias (-109V) not switching to the required low level with key down.
8 Soft Transmit PIN diode back bias below minimum required value key up.
9 Soft Transmit PIN diode forward current below minimum required value key down.
11 Soft Transmit PIN diode forward current exceeds maximum limit key down.
12 Soft Excessive input reflected power.
13 Soft Excessive and unsafe drive power.
14 Soft Excessive load reflected power or RF voltage. May be caused by excessive load VSWR at an otherwise acceptable power (e.g. 4:1 at 1.5 kW) or excessive power at otherwise acceptable load VSWR (e.g. 2.5 kW at 1.9:1).
16 Soft Plate current greater than 1.35 amp for more than 4 seconds continuous. Note: The IP button LED flashes for several seconds before a fault 16 IP trip occurs.
17 Soft Abnormally low or high amplifier power gain. Usually due to extreme mis-tuning or possibly an RF arc.
18 Soft Filament current less than 2.0 amp. Possible open tube filament.
20 Soft Filament current greater than 3.5 amp. Possible shorted filament.
21 Soft Excessive tube temp. in transmit (key down); abnormal dissipation and/or insufficient airflow.
22 Hard Control system fault; D/A feedback) not working.
23 Hard Control system fault; D/A feedback 1 not working.
24 Hard System voltage fault. High voltage, +/-15 volts, or 109 volts below safe operating level.
26 Soft RF drive before or without amplifier keyed (possibly mis-sequenced T/R), or attempted automatic band change with excessive RF drive.
29 Soft Attempt to transmit on invalid frequency, such as above 24 MHz without unlocking 24-30 MHz coverage.
31 Soft Excessive grid current; above 100mA continuously for 2 seconds. NOTE: Red LED in IG bargraph flashes before IG trip occurs.
33 Soft Control system fault; TUNE capacitor not initializing.
34 Soft Control system fault; TUNE capacitor not moving or zero sensor position not working.
35 Soft Control system fault; LOAD capacitor not initializing.
36 Soft Control system fault; LOAD capacitor not moving or zero sensor not working.
37 Hard Control system fault; Bandswitch not moving.
99 Fault 99 Unit refuses to turn on. Same hard fault occured 6 consecutive times without one successful power-up.

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