Watlow QPAC Modular SCR Power Control Service Manual de usuario descargar pdf (Pagina 19)

bad. The resistor will usually be black or dark brown if open. It should read a mini-

mal voltage of < 1V. If it reads line voltage R10 is bad. See Page 5 for ordering a

replacement transformer.

The QPAC Mother Board is Bad

Check the DC voltages at the J1 connector. Place the voltmeter common on pin 7

or 8. They should read as follows:

J1 Connector Label Without Card With BF, AF or AL

Test Point Card Installed

1 T STAT Not Used 3 to 5V

2 -V -11 to -14VDC -15 to -22VDC

3 FWZ* 11 to 14VDC 11 to 14VDC*

4 +V 15 to 18VDC 15 to 18VDC

5 Q32, connected to Pin 1

Q01 or Q33 Not Used Not Used

6 +5V 5V ±0.1V 5V ±0.1V

7 COM

8 COM (meter common)

9 KEY

10 COM

11 +LED Not Used Pulses possible

12 COM

*See scope pictures on Page 31.

Problem: Full or Partial Uncontrollable Heat

The SCR Switch is Shorted

Remove the control card and power up the QPAC. The output should be OFF. If

the unit is still full ON, remove power and disconnect the load wires and measure

across L1 and T1 with an ohmmeter. If resistance is low (5Ω or less), the SCR is

shorted and must be replaced. See Page 5 for ordering a replacement SCR.

A Heater is Partially Shorted or Shorted to Earth Ground

Disconnect the control card; the output should be OFF. If not, disconnect the

power and heater, and measure the heater resistance. It should match the heater

KW rating.

The Control Card has the Wrong Bias Adjustment

The bias adjustment is set too high and needs to be readjusted. See the Bias and

Gain Adjustment procedure with the appropriate control card on Page16.

The Control Card is Bad

First, try to re-seat the control card. Make sure there is a good connection between

the control card and the mother board. Power down the control and remove the

control card. Power up without the control card installed. If there is no heat, the

control card is bad. Replace the control card. See Page 5 for ordering.

An Excessive Input Signal from the Temperature Control

Check the input signal for proper calibration (i.e. 4-20mA at 4mA). The output

should be full OFF. At 20mA the output should be full ON.

The QPAC Mother Board is Bad

Refer to the mother board troubleshooting procedure on Page 28.

WATLOW QPAC Service Manual 19

Troubleshooting, Chapter 5

Q01

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