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

Remarks

Gain Control

Driver Stage

Final Amp

Manual Text

4-5

REV -