Technical_reference - 第21页
Technical Service Manual 21 Revision Dat e: August 2004 TEM PERA TURE DRIFT FROM A NEARBY HEA T ER A Cell temper ature is higher than s et point, not m ore than 10 o C, and stable. POSSIBLE CAUSES The problem is mos t li…
Technical Service Manual 20 Revision Date: August 2004
3. External air forced into heat tunnel See: 30
COLD SOLDER JOINTS
1. Conveyor speed See: 22
2. Dirty circuit board See: 23
3. Old solder paste See: 24
4. Cell fan motor malfunction See: 3
Technical Service Manual 21 Revision Date: August 2004
TEMPERATURE DRIFT FROM A NEARBY HEATER
A Cell temperature is higher than set point, not more than 10
o
C, and stable.
POSSIBLE CAUSES
The problem is most likely the result of temperature drift from a nearby Cell. The recommended method to locate
the offending Cell is to turn off the nearby Cell heaters one at a time, and look for a change in the symptom when each
one is off.
Refer to the “HEAT CELL ARRANGEMENT” illustration, and consider the following possibilities on all sizes of ovens: *
If Cell 3T temperature is higher than set point, then Cell 3B, 2T, 2B, 4T, or 4B could be at fault.
If Cell 4T temperature is higher than set point, then Cell 3T, 3B, or 4B could be at fault.
The Cell slot settings can cause thermal drift: Cell 4T’s left slot open and right slot closed could cause thermal drift from
Cell 4T to Cell 3T.
CELL FAN MOTOR MALFUNCTION IN AN NEARBY CELL
A Cell indicates an over- temperature condition of not more than 10
o
C above set point and is stable.
This is may be the result of a Cell Fan Motor malfunction in a nearby cell.
POSSIBLE CAUSES
The TC senses a combination air/IR temperature. When the fan fails, the controller will try to heat the metal heater plate
hot enough to read normal set point. The heat that is radiated is then absorbed into the air of an adjacent cell, causing
the adjacent cell to go above set point.
HINT: If a stopped motor is suspected, visually check the heat slinger fan blades. The heat slinger is a set of fan blades
mounted directly on the motor shaft between the motor and the outside of the cell. If the heat slinger is turning, the motor
is turning. The motor should be turning in a counter clockwise direction as viewed from the outside of the cell. If the oven
has the Individual Cell Fan Sensing Option check for an LED that is lit, indicating a cell motor that is not turning.
See Heat Cell cross-sectional Diagram in “A-HEATING CELL DESCRIPTION”
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Technical Service Manual 22 Revision Date: August 2004
CELL FAN MOTOR MALFUNCTION
A Cell Fan Motor malfunction can produce the following symptoms:
1) A Cell slowly reaches setpoint.
2) Cold solder joints on the product.
CHECK: Rotation of the Motor can be confirmed by a visual check of the heat slinger fan mounted on the motor shaft
between the Motor and the Cell. During normal operation, the heat slinger fan turns counter clockwise as viewed from
the outside of the cell.
SYMPTOM # 1
A cell over temperature approximately 10
o
C during startup,
POSSIBLE CAUSES
With this symptom, some careful investigating is necessary to find the problem. If the blower motor malfunctions, the
heat at the T/C will not change much. There will not be any convection in that zone, creating the possibility of temperature
drift from an adjacent heat zone.
SYMPTOM # 2
A Cell slowly reaches setpoint.
POSSIBLE CAUSES
This condition may occur when the motor is non-functional and the oven is just starting up. If the motor is not blowing air,
the Zone will take longer to heat up and the temperature at the faulty Cell will not reach set point. The T/C in the faulty cell
will sense the Infrared radiation from the Heater Panel
SYMPTOM # 3
Cold solder joints on the product.
POSSIBLE CAUSES
Check for a group of fans not operating because of a tripped circuit breaker or because of an Inverter malfunction.
If cold solder joints on the product may be an indication of a faulty fan in just about any location in the oven. The heat
transfer in the oven works by air volume and velocity. If a fan is not operating, the T/C for that cell could still register the
approximate correct temperature because the heater panel has reached the temperature setpoint. The amount of
convection in that zone will be significantly lower than normal. Since the heat is transferred by air moving over the
components and joints of the product, smaller airflow produces less heat transfer.
The faulty fan could be anywhere in the oven because if the product is not up to the required temperature upon entering
the reflow zone, it will probably not be at the “reflow temperature” for the required time. (Cold solder joints can be
produced if the preheat is incorrect, the preflow temp is low, or the reflow temp is low)
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