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STT40 / STT70
Troubleshooting 9-1
9. Troubleshooting
9.1. Introduction
The utmost in safety precautions should be observed at all times when working on or
around the machine and the electrical components. All normal trouble-shooting must
be accomplished with the power off, line fuses removed, and with the machine
tagged as out of service.
The use of good quality test equipment cannot be over-emphasized when
troubleshooting is indicated. Use a good ammeter that can measure at least twice the
AC and DC current that can be encountered for the machine. Be sure that the
voltmeter has at least minimum impedance of 5,000 OHMS-per-volt on AC and
20,000 OHMS-per-volt on DC scales. Popular combination meters, VOM and
VTVM can be selected to provide the necessary functions.
Before making haphazard substitutions and repairs when defective electrical
components are malfunctioning, we recommend that you check the associated
circuitry and assemblies for other defective devices. It is common to replace the
obviously damaged component without actually locating the real cause of the trouble.
Such hasty substitutions will only destroy the new component. Refer to wiring
diagrams and schematics.
Locating mechanical problems, should they occur, is relatively straightforward.
When necessary, refer to the parts catalog section.
Problem Possible cause Corrective action
Dirty filter. Clean or replace filter.
Desiccant beds are contaminated
by material or plasticizer leaking
into the system.
Replace desiccant. See Page 42
for more information.
Blower overload has tripped.
Fix the problem and reset the
overload.
Little or no air coming from
the process delivery tube.
Blower fins filled with dust or
contaminants.
Remove blower side plate,
clean baffles, replace.
Suction in delivery tube,
pressure from the return tube.
Phase is reversed on power drop
coming into the dryer.
(Note: on STT 70 only)
Stop the dryer.
If the dryer was connected to
the drying hopper, check to see
if the desiccant and process air
heater has been contaminated
with resin.
If so, replace the desiccant and
remove any resin carry-over.
Otherwise, change the phase of
two legs of the three-phase
power drop.