Interscan Corporation GF1900, Manual

Page: 12 / 23

SULFURYL FLUORIDE MANUAL REV C PAGE 12 OF 23 04/07/11
TROUBLE SHOOTING
READY light does not illuminate.
Check that the POWER L.E.D. is illuminated. If it is not:
1) Check the main fuse.
2) Check that the rear connector is tight.
3) Check the power source for a nominal 24V.
4) Check that the circuit board connector is tight.
If POWER L.E.D. is illuminated:
1) Carefully check if the furnace is cold.
2) If furnace is cold, check for an open 4A fuse.
3) If fuse is good, disconnect the power source
and connect an ohmmeter across the furnace
support brackets. The reading should be less
than 5 ohms.
If the furnace is good, re-connect the power source and turn the analyzer on.
With a DVM, check the voltage at the Q4 regulator output. It should read
16.45V or greater to allow proper warm up time of 6 to 9 minutes. Adjustments
are performed by turning the potentiometer screw of R12.
If regulator output is normal, check for the same voltage at Q5 base and for 24V
at the collector. Normal readings here indicate a failed Q5, or discontinuity
between the furnace and emitter, or furnace and ground.
To check Q4:
1) If Q4 output is close to zero and feels hot, C7
may be shorted.
2) If Q4 is cool, check for 24V at the input.
3) Check the voltage at the "R" terminal. If it
is 1V or less and the output is around 2V, Q1
has failed or is being activated.