Amplifier Research 100A250A Manual - Page 18
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Model 100A250A
4.3.5 Voltage/Amplifier Faults (Schematic Diagram Nos. 1010659)
The model 100A250A fault circuits sense voltage faults from PS1 (+15V) and PS2 (+15V). They also
sense an over current fault in the final amplifier stage.
4.3.5.1
4.3.5.2
4.3.6 Low or No Power Output (DC Tests) (Schematic Diagram No. 1010659)
All indicators on the Model 100A250A VFD are normal, the VFD indicates "POWER ON" and
"STATUS OK," and the cooling fan (Blower B1) is operating.
4.3.6.1
4.3.6.2
Is the coaxial cable okay?
4.3.6.3
Feed-through Cap.
A3 C9
A3 C12
A1 C1
A2 C1
A2 C2
Note: The locations of the feed-through capacitors can be found on the RF Assembly Drawing
(Schematic Diagram No. 1010657).
Power Supply Faults (Schematic Diagram 1010659). PS1 and PS2 send BUSS OK signals
to the operate/control board (A4). These signals give an early indication of over voltage or
over current conditions. If either condition occurs the power supplies send a fault signal to
the operate/control board which in turn sends a disable signal to the power supplies turning
off the outputs.
The Final Amplifier Assy Faults. (Schematic Diagram 1010659 and 1007520). The final
amplifier incorporates two stage protection for the output transistors. U1 monitors the
device current which is normally 7.4 amps. If the amplifier is over driven so that the
current rises to 10.5 amps U1 will decrease the bias voltage thereby decreasing the current.
If the amplifier is over driven to the point that the active bias cannot control the current to
less than 11.5 amps U4 will generate a fault signal which will turn the power supplies off.
Check the RF input to the unit—is it the correct amplitude and frequency?
Check the RF output connection from the unit—is it correctly connected to the load?
Check the voltages at the following locations. Troubleshoot any incorrect voltages.
Normal Voltage
+12V
-12V
+30V
+30V
+30V
Remarks
Gain Control
Gain Control
Driver Stage
Final Amp
Final Amp
Manual Text
4-5
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