Teledyne 514 Instruction Manual page 48

5.0 Maintenance & Troubleshooting
Adjustment of R10 and R11 on Chopper-Stabilized Log
Amplifier Circuit Card
When the log amplifier integrated circuit (A1) is replaced on the
chopper-stabilized log amplifier circuit card, it is necessary to readjust
potentiometers R10 and R11 in order to balance the circuit.
In order to make the necessary adjustments, it is necessary to have an
extender card, one 20K resistor, and a high impedance voltmeter.
Proceed as follows:
1. Use an extender card so that connections are accessible
2. Temporarily connect a 20K resistor (stable, not composition type)
between A1-2 and A1-7 (across C2).
3. Unplug A2, A3 and A5.
4. Jumper A5-7 to A5-5 at socket and A2-3 to A2-6 at socket.
5. Install card in card extender and turn on analysis unit power.
6. Verify that voltage to pin 7 of the card edge connector is
approximately 9 VDC (measure between pin 7 and pin 14).
7. Adjust potentiometer R10 until the voltage measured at A1-7 is
zero with respect to signal common (TP3).
8. Remove jumpers installed in step (4).
9. Remove resistor connected in step (2).
10. Disconnect connector pin 7 from input by lifting a connection on
the extender card.
11. Temporarily connect a 20K resistor between A5-7 and A5-15 to
A1-16.
12. Jumper between A5-6 and A5-7 to provide the 9 VDC through
20K into A1-2 and through 20K into A1-16.
13. Adjust potentiometer R11 until the voltage measured at TP2 is
zero.
5–10
Teledyne Analytical Instruments
A Business Unit of Teledyne Electronic Technologies