Teledyne 514 - NDIR analyzer - Manual (Page 54)

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5.0 Maintenance & Troubleshooting
Teledyne Analytical Instruments
A Business Unit of Teledyne Electronic Technologies
1. TP1 (Violet): The clamped video should be between -0.4 to –
2V P-P volts. The base line is clamped to ground. Screen the
optical beam to achieve -0.4 to -2 volts P-P.
2. At this time set the gain of amplifier A1 to approximately 100. To
accomplish this, it is necessary that the peak level detector PCB
not be in place due to the fact that it is part of the AGC loop.
a. Connect one lead of a dual trace oscilloscope to TP2
(gray), the other to TP3 (green).
b. Set the attenuation so that the signal at TP2 is attenuated
by a factor of 100 compared to the one at TP3.
c. At this point you may note that the wave form at TP3 is
saturated. To get it out of saturation simply place screens
in the light path until a good trace is obtained.
d. Adjust P1 until both wave forms are the same. (Note:
actually 100 to 1)
3. Remove required screens in the light path to bring the voltage at
TP1 (violet) back between -0.4 to -2 volts P-P. Install the peak
level detector PCB. With the scope at TP3 of the AGC you
should see the wave form come out of saturation due to AGC
control.
4. Connect one input of the oscilloscope to TP5 on the Switch
Driver and clamp. Connect other input to TP3 on AGC. The
spike should be close to the halfway point between the negative
going peaks at TP3. It does not have to be exact as long as it
doesn’t coincide with the signal. If the spike is off, move the filter
wheel position sensor. If the spike falls on the signal it will clamp
it to ground.
5. After adjusting the sensor recheck Section 1.6, Switch Driver and
Clamp Circuit.
Peak Level Detector (PLD) PCB
Refer to Table IV.
1. With the oscilloscope leads at TP1 (red) and TP2 (blue) adjust
R3 until the two wave forms are of equal size.
2. With an oscilloscope lead at TP3 (yellow), adjust R15 until the
square wave is reduced to 20 mV P-P or less (best straight line).
3. Repeat step 2 with a scope lead at TP4 (orange) using R14 for
adjustment.