Barnstead International Thermolyne 859 Series, Service Manual

Page: 70 / 118

70
E
RRORS
Error (cont.)
Tests never end
(Complaint)
Burn ticket indicates
the load actually
gains weight
(Complaint)
Unit will not heat up
but displays appear
normal (Complaint)
Symptom (cont.)
If the sample does not lose more
than 15 grams at the end of the
15th minute, the software is pro-
grammed not to detect an endpoint
and the test will run until stopped
by the end user. (Written into
software due to early aggregate
calibration procedures.)
Support posts may be touching or
rubbing as may the ceramic plate
or basket in the chamber.
Evaluate basket. As baskets age,
they may start to warp, especially
when introduced in a hot chamber.
If the area ambient temperature is
below 50°F, the main microproces-
sor will not recognize the milli-volt
signal generated by the thermocou-
ples.
Action (cont.)
Perform a test in which minute by minute test
results are printed out. Examine the burn ticket
& note the weight loss at the 15th minute. If not
greater than 15 grams, unit is performing as it
should. (See Sample Ticket Section.)
Perform a hidden key 2 routine and attempt to
burn a 1500 gram sample. Initial sample may
have been too large.
Recalibrate balance or replace balance. (See
Balance Section.)
Inaccurate temperature indication on display.
Verify chamber temperature with an external
N.I.S.T. Pyrometer and probe. Calibrate tem-
perature.
Ensure samples are being leveled off in bas-
kets. DO NOT MOUND SAMPLES, as the
internal portions of the sample may not burn out
Completely due to the lack of oxygen to burn.
Ensure all are centered and try running another
sample. (See Sample Ticket Section.)
Warping may cause the basket to rub against
the chamber. Basket(s) may need to be
replaced.
Recalibrate balance. (See Balance Section.)
Replace the balance.
Attempt to warm the tip of the chamber thermo-
couple by holding it in the flame of a match for
15 seconds. Close chamber door and see if unit
starts to heat.
Use a portable space heater to warm the elec-
tronics of the unit. Allow 15 to 30 minutes for
NCAT to warm.