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Before you call, please look at this section to see if your question is covered here. If you do call for technical
assistance, be ready to supply the following information:
• complete model number of controller
• symptoms of the problem
• unusual events, if any, that preceded the problem
• remedies you have already tried
Symptom. Controller dead. No output
Check - Verify 120/240 Vac, 50/60 Hz input voltage. Check
heater for shorts. Look for open breakers or open external
fuse. Remove input power. Check continuity through power
transformer primary. With ohmmeter, read between pins: 8
and 9 for 225 or 450 ohms +/-10% and 8 and 10 for 680 or
1000 ohms +/-10%
Probable Cause.
- No line voltage input
- Open PC board to back- plate connector
(defective connector)
- Open power transformer
Corrective Action
- Replace heater, if shorted
- Restore power
- Replace either power transformer or backplate connector
Symptom. No output, step 1 ok, meter
nulls at ambient
Check - If no readings in either step above, remove controller
from housing and repeat resistance measurements as above,
but directly on PC board lands corresponding to pins 8, 9, and
10. Correct readings indicate open PC board to backplate
connector problem. Incorrect readings indicate power
transformer problems.
Visually inspect relay contacts. Heater continuity and wiring
Probable Cause.
- External backplate jumper missing (all
models except “S” and “F”)
- Defective relay
- Open heater or heater circuit wiring
Corrective Action
- Install jumper
- Replace relay if contacts are worn or dirty
- Replace open heater, correct defective wiring
Symptom. No output, meter reads full
scale positive, no heat
Check - T/C continuity. Disconnect T/C connections from
instrument. Measure T/C circuit resistance. Ohmmeter should
read 100 ohms or less.
Probable Cause.
- Open thermocouple or T/C wiring
Corrective Action
- Replace T/C. Correct defective wiring
Symptom Full output, no control. Ouput
light stays on
Check - Connection polarity. T/C wires are color-coded. Red
is the negative (-) lead. (for U.S.A.) T/C lead wiring.
Probable Cause.
- Thermocouple connections reversed
- T/C lead wires shorted between T/C and
control
Corrective Action
- Connect correctly
- Repair or replace
Symptom. Full output, no control.
upscale
Check - Disconnect power and load. Measure resistance
between pins 12 and 13. Should read innity.
Probable Cause.
- Relay contacts welded closed
Corrective Action - If resistance reading is near 0 ohms,
replace relay.
Symptom Process control temperature
an external pyrometer. Deviation meter
nulls and process is stable.
Check - Check T/C lead wires at back of probe Wire color
indicates type of T/C
- Verify type of wire
Probable Cause.
- T/C lead wires shorted close to process
- Wrong type of T/C being used, etc.
- Standard electrical wiring being used in
place of T/C wire
- Gradient error.
Corrective Action
- Replace defective wiring
- Install correct T/C for temperature range of instrument. See
instrument serial number tag for T/C type.
- Run only T/C wire between process and controller.
- Use electronic indicator in parallel with suspect instrument’s
T/C input
Troubleshooting
NOTE:
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