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C7076A,D ADJUSTABLE SENSITIVITY ULTRAVIOLET FLAME DETECTORS
3. If the shutter is closed and the signal at the Flame
Current jack on the detector is 1 microampere or more,
remove the ultraviolet sensing tube (see Service
section) and operate the detector.
a. If the shutter opens, replace the 191053 Ultraviolet
Sensing Tube.
b. If the shutter stays closed, replace the plug-in
electronics chassis (see Service section).
4. If the flame signal measured at the Flame Current jack
on the detector is weak (less than 1.4 microamperes),
proceed as follows:
a. Clean the sight pipe. Make sure there are no
obstructions in it.
b. Clean the viewing lens with a soft, clean cloth.
c. Make sure the sensitivity control on the plug-in
electronics chassis is not set too low for the flame
conditions encountered. (Refer to Adjustments and
Checkout section.)
d. Resight the detector. See Planning the Installation
and Installation sections.
5. If the flame signal measured at the Flame Current jack
on the detector is strong (greater than 1.4
microamperes), but the flame relay does not pull in,
connect a dc voltmeter (capable of measuring 50 volts)
across terminals 6 (F) and 5 (G) on the terminal block (F
is +; G is -).
a. If the voltage is less than 5 volts and the shutter is
not oscillating, disconnect the F leadwire from
terminal 6 for a moment.
(1) If the voltage (5 to 6) rises, trace the wiring
between the detector and the flame safeguard
control (refer to Fig. 14 or 15). If the wiring is
correct (no short circuits), replace the plug-in
R7476A or R7886 Dynamic Self-Check
Ultraviolet Amplifier.
(2) If the voltage (F to G) does not rise, replace the
plug-in electronics chassis (see Service section).
b. If the voltage is 5 volts or more, check the F and G
leadwires between the detector and the flame
safeguard control. If they are wired properly (no
open circuits), replace the plug-in R7476A or R7886
Dynamic Self-Check Ultraviolet Amplifier.
6. If the previous actions have not corrected the problem,
replace the plug-in electronics chassis.
SERVICE
WARNING
Electrical Shock Hazard.
Can cause serious injury or death.
Open the master switch before removing or installing
the plug-in electronics chassis or the detector.
WARNING
Fire or Explosion Hazard.
Can cause serious injury or death.
Make sure that the environment surrounding the
C7076D Flame Detector is free of all explosive or
hazardous conditions before exposing the interior of
the detector to the atmosphere during the
performance of the following troubleshooting
procedures.
95-8269—1
IMPORTANT
If the combustion chamber (C7076A Flame Detector)
has a positive pressure, make sure the aspirator inlet
pressure equals or exceeds that required for sight
pipe seal off, as given on Fig. 9, before unlatching
the detector.
IMPORTANT
Only qualified flame safeguard technicians should
attempt to service or repair flame safeguard controls
and burner management systems.
Periodic Maintenance
1. Scheduled replacement of the detector components is
not necessary.
2. Keep the flame detection system adjusted for safe and
reliable operation
3. Clean the viewing lens regularly. Use a soft, clean cloth.
If the lens is damaged, or if it is coated with a substance
which cannot be cleaned off, replace it (see
Maintenance Procedures, following).
4. C7076A Detector only: Replace the silicone-rubber
gaskets which seal the front and rear cover plates if they
are damaged or deteriorated (see Maintenance
Procedures, following).
Maintenance Procedures
CAUTION
Equipment Damage Hazard.
Improper part replacement can damage the
equipment.
Before making a replacement, make sure you have
the correct part (check its part number and voltage
rating).
Replacing the Plug-In Electronics Chassis
REPLACING THE PLUG-IN ELECTRONICS CHASSIS IN THE C7076A
FLAME DETECTOR
1. Open the master switch to interrupt all power to the
detector.
2. Loosen the four captive screws in the rear cover plate
and remove the plate.
3. Remove the four standoffs that hold the plug-in elec-
tronics chassis and pull the chassis out of the housing.
4. Align the slot in the top of the new chassis with the key
in the housing.
IMPORTANT
Make sure the part number and the voltage rating of
the new chassis are correct.
5. Insert the new chassis in the housing and firmly push it
all the way in (see Fig. 18). Make sure the octal plug on
the chassis is securely seated in the socket in the
housing.
6. Insert the four standoffs that hold the chassis and
tighten them securely.
7. Close the master switch and perform the Adjustments
and Checkout.
8. Put the rear cover plate back on and tighten the four
screws securely.
18
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