Technical_reference - 第20页

Technical Service Manual 20 Revision Dat e: August 2004 3. External air for ced into heat tunnel See: 30 COLD SOLDER JOINTS 1. Convey or speed See: 22 2. Dirty circuit board See: 23 3. Old solder paste See: 24 4. Cell fa…

Technical Service Manual 19 Revision Date: August 2004

UNDER TEMPERATURE PROBLEM.

CELL TEMPERATURE RISES, BUT DOES NOT REACH SET-POINT:

1. No power to heater:

2. Open circuit breaker See: 10

3. Control SSR failure See: 12

4. Loose wire See: 16

5. Open heater element See: 13

6. Shorted thermocouple See: 18

7. Excessive exhaust flow See: 14

8. Excessive air entering oven See: 15

9. Under voltage or Phase failure See: 19

Cell appears to stay cold:

1. Thermocouple short See: 18

2. Controller failure See: 11

3. General oven failure See: 20

Temperature drops down below set point:

1. Power loss to heater. See: 19,21

2. Control SSR failure See: 12

3. Thermocouple short See: 18

4. Controller failure. See: 11

5. Radical recipe change See: 31

RANDOM HIGH TEMPERATURES.

1. Thermocouple connection See: 25

2. Grounding. See: 28

3. Conveyor motor noise. See: 26

4. Failure of control SSR See: 12

5. AC Signal on T/C or T/C Wires See: 27

RANDOM LOW TEMPERATURES.

1. Failure of control See: 11

2. Erratic exhaust. See: 14

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

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

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”