Teledyne 514 - NDIR analyzer - Manual (Page 47)

5–9
Maintenance & Troubleshooting 5.0
Teledyne Analytical Instruments
A Business Unit of Teledyne Electronic Technologies
given more as an indication of magnitudes to be expected rather than as
exact values.
The troubleshooting chart cannot possibly identify all malfunctions that
may occur. Isolate the malfunction by using the waveform/voltage informa-
tion, then replace the suspected circuit card.
All schematic and and circuit assemblies are given in the Drawing List
in the Appendix.
Adjustment of R7 and R9 on Log Ratio Amplifier Circuit
Card
When the log amplifier integrated circuit (A1) is replaced on the log
ratio amplifier circuit card, it is necessary to readjust potentiometers R7 and
R9 in order to balance the circuit.
In order to make the adjustments, have an extender card, a 100K
resistor for connection between A1-2 and A1-7 (across C5), and a high-
impedance voltmeter handy to measure the voltage between A1-7 and
connector pin 9.
Proceed as follows:
1. Temporarily install 100K resistor across A1-2 and A1-7 (across
C5).
2. Disconnect connector pin 9 from 9 VDC by lifting a connection
on the extender card. Connect pin 9 of printed circuit card to A1-
1 (signal common).
3. Adjust R7 until the voltage measured at A1-7 is zero.
4. Remove 100K resistor from A1-2 and
5. Reconnect connector pin 9 to 9 VDC.
6. Using a high-impedance voltmeter to measure voltages at pins 7
and 9 of the card extender, adjust R3 on the peak detector circuit
card until they are equal. With the reference and measuring
voltages equal and at approximately 9 volts, adjust R9 of the log
circuit card until the voltage at A1-10 is zero.
7. The log amplifier module (A1) is now balanced.