Teledyne 514 Instruction Manual page 58

5.0 Maintenance & Troubleshooting
13. Adjust potentiometer R11 until the voltage measured at TP2 is
zero.
14. The log amplifier integrated circuit A-1 should now be balanced.
15. Remove the 20K resistor and the jumper. Restore connections,
replace IC's, turn on the instrument power, and check control
loop by measuring voltage at the output of A2. Voltage should be
-3 VDC, nominal.
16. If voltage is positive, R11 is out of balance or a component in the
loop has failed. A slight adjustment of R11 (no more than 2 or 3
turns) should cause the voltage to change polarity to give the
required negative voltage at pin 6 of A2.
17. Check pins 8 and 10 on amplifier A3 for presence of +5 volt
square wave on the oscilloscope.
18. Switch NORM/REF to REF. Adjust R36 to give 90% of scale (9
VDC) on the analysis section meter.
19. Switch to MEAS. Meter should read 9 VDC.
20. Switch the NORM/ZERO switch to ZERO position. Adjust the
coarse ZERO to cause the meter to read zero. The ZERO control
should end up around 500.
21. The remainder of the adjustments on this PCB must be made by
TAI Photometric personnel
Chopper Stabilized Adjustable Log Ratio Amplifier
(Dual Log Board)
See dwg. C-17706. The dual log circuit is used when it becomes
necessary to unequally balance the logarithmic waveform of the reference
voltage and the logarithmic waveform of the measuring voltage so that an
interfering, NIR absorbing, background compound can be cancelled out.
When an interfering compound, in a three or more component mixture,
absorbs more at the selected reference wavelength than it does at the measur-
ing wavelength, the dual log PCB affords a means of balancing, and thereby
cancelling, these inequalities. This type of compensation is only necessary in
a three or more component mixture. It is not necessary where only two
compounds are present.
1. When the adjustable log ratio board is used, disable the AGC
circuit by removing A3 and A4 on the AGC board (B-14430).
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Teledyne Analytical Instruments
A Business Unit of Teledyne Electronic Technologies