Barnstead International Thermolyne 859 Series, Service Manual

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positive terminal. Pin “4” is the DC negative ter-
minal. Refer to page 96.
8) Power on the NCAT unit.
9) Allow the NCAT to step through the startup
countdown and go into the preheat mode.
10) Note if the CYCLE FILTER and CYCLE CHAM-
BER LED’s illuminate on the front control panel.
a) These LED’s indicate the main microproces-
sor control board is attempting to apply power to
the solid-state relays. If they are not illuminated,
the solid-state relays should not have power
applied to them and the main logic board may
be defective.
11) How to determine if a solid-state relay is defec-
tive:
a) A solid state relay can be considered good, if
the input of the relays (pins “3” and “4”) have a
5 to 15Vdc signal applied across them and at
the same time no AC voltage can be measured
across pins “1” and “2”.
b) A solid-state relay is also considered good, if
the input of relay, pins “3” and “4”, have no DC
voltage signal applied across them and at the
same time an AC voltage can be measured
across pins “1” and “2”.
c) A solid state relay is considered defective, if
the input of the relays (pins “3” and “4”) have a
5 to 15Vdc signal applied across them and at
the same time full potential line voltage (AC) can
be measured across output pins “1” and “2”.
12) To test the blower motor (exhaust fan) solid-
state relay, activate the blower motor by press-
ing the start/stop key to initiate a cycle run.
(The blower motor is not activated in the preheat
mode. Only when a cycle is being run in the
test mode!) If the blower motor turns on, your
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