HindlePower AT30 SERIES Operating And Service Instructions page 56

SERVICING THE AT30
PROBABLE
SYMPTOM
CAUSE
Front panel is 1. Control
dead, but ac boards are not
and dc connected
voltages are
present at
2. Defective
TB1
Main Control
PC Board (A1)
3. Defective
wiring
Front panel 1. Defective
dies during ac Power Supply
power failure Ballast Resistor
and dc (R3)
voltage is
present at
TB1
2. Defective
wiring
AT30 output 1. Defective
voltage too SCR
high, or not
controllable
2. R4 or R14 is
defective, or
wrong value
3. Defective
temperature
compensation
probe (optional)
4. Defective
Main Control
PC Board (A1)
52
RECOMMENDED ACTION
1. Make sure the Gate Driver PC B oard (A15) is firmly
connected to the Main Control PC Board (A1) via plugs (J17 to
P17). Make sure the two signal harness plugs are firmly
inserted into the Gate Driver PCB connectors (J25 and J26).
2. If the AC ON indicator is lit, but the rest of the front panel is
dead, replace the Main Control PC Board (A1).
3. Check the two harness wirings to the Gate Driver PC B oard
(A15) connectors (J25 and J26) for signs of insulation
damage, burns, etc. Confirm all wires are securely crimped in
the connector.
1. Use a dc voltmeter to measure the voltage from TB1(-) to J1
pin # 8 on the Main Control PC Board (A1). It is normally 12
Vdc when the rated dc output voltage is present at TB1(+/-).
If it is not 12 Vdc, remove all power from the AT30, and
measure the resistance of R3 from TB1(+) to J1 pin # 8. See
the table in Section 3.6 for the proper resistance value. If the
resistance is not within 10% of the table value, replace R3.
2. Remove the safety shield, and check the wiring to and from
TB1 and the Main Control PC Board (A1) for signs of
insulation damage or burns. Repair any damaged wiring.
1. Disconnect the wire harness plug from connector J26 on the
top of the Gate Driver PC Board (A15) and restart the AT30. If
you are able to measure output current, one of the SCRs is
defective. Replace the rectifier module(s) (A16) as needed.
2. See page 61 of Section 3.5. Locate R4 and R14 on the
Gate Driver PC Board (A15). Remove one end of each resistor
and measure its value with an Ohmmeter. See the table in
Section 3.6 for resistance values. If either resistor is not within
1% of the specified value, replace R4 and/or R14 as needed.
3. Remove one of the probe leads from TB8 and measure its
resistance. At 77 °F / 25 °C the resistance should be about
Ω
10,000 . If it is not, replace the probe assembly (A10).
4. If the front panel meter displays more than 110% of rated dc
current, the Main Control PC Board (A1) may be defective.
Unplug the system harness connectors (J25 & J26) from the
Gate Driver PC Board (A15). If the output current drops to
zero, replace the Main Control PC Board (A1).