Procedure For Replacing Pc Boards - Lincoln Electric RANGER 405D Operating Manual

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Table Of Contents

Table of Contents

Brief Operating Description

The Ranger 405D has 5 separate PCBs. These are:

1) Watcher/Idler PCB – mounted on the rear of the control

panel.

2) Auxiliary Current Sensor PCB – mounted on the rear of the

Auxiliary output module.

3) Rotor / Weld Control PCB – mounted behind the control

panel.

4) VRD PCB - mounted behind the control panel.

5) Volt and Amp meter model PCBs mounted on the rear of the

control panel (where fitted).

When fault finding the PCBs ensure that all connecting plugs are

fully inserted in their respective sockets and that all connector

pins are in good, clean condition.

A general knowledge of the PCB's operation is required before

attempting to fault find. Light emitting diodes (LEDs) are used on

the following PCBs to indicate the boards operational status.

1) Watcher/Idler PCB

The engine watcher/idler PCB is powered from the 12 volt battery

(negative ground). Note, never disconnect the battery after

starting the engine, as control voltage to the PCBs will be lost.

This PCB is activated when the keyswitch is on. Correct operation

of this PCB provides a ground return for relay [R3] to be activated.

Relay [R3] switches the supply voltage to the fuel solenoid and

the rotor control PCB. LED [L4] illuminates to confirm fuel & rotor

control "OK".

LEDs L5, L6, L7 & L8 are visible through to the nameplate. They

are normally "off" and indicate the engine and electrical

temperature/fault alarms. The first engine alarm will inhibit the

others from indicating and remains illuminated until the key switch

is turned to the 'off' position. Turning the key switch to "start"

position initiates a 10 seconds over-ride timer allowing the engine

to start.

LED 5 is illuminated when the over-ride timer/alarm inhibit circuits

are active in the "shutdown" condition. If a fault condition still

exists, the engine will again be shut down after the 10 seconds

over-ride period expires.

LEDs L2 & L3 indicate the engine idler functions. LED 3

illuminates representing a 1 second pulse to Relay [R1] which

energises the "pull in" winding in the idler solenoid. LED 2

confirms energisation of Relay [R2] and then the "hold" winding in

the idler solenoid.

The idler control section of the PCB uses an input signal from the

rotor/weld control PCB and/or an input signal from the auxiliary

current sensor PCB to determine when the engine is to go to high

idle speed. When the input signals cease a 12 second timer is

initiated and times out before the engine goes to low idle speed.

The "idler" switch on the front panel when switched to '

position bypasses the idler circuitry so that the engine runs

continuously at high idle speed.

2) Auxiliary Current Sensor PCB

This PCB uses a "Hall Effect" device to sense the magnetic field

generated in the Auxiliary supply leads when a current passes

through them. It is powered from the watcher/Idler PCB and

returns a signal back to this PCB.

3) Rotor / Weld Control PCB

The rotor/weld control PCB supplies 12V to the rotor for 'flashing'

and initialising the Automatic Voltage Regulator (AVR). The AVR

is factory set to maintain a nominal 230V/400V auxiliary voltage

output.

The AVR monitors the 3 stator field windings and then regulates

a 'half controlled 3 phase bridge rectifier' which supplies the rotor

DC voltage. LED's (L4) (L5) & (L6) should illuminate to the same

brilliance to verify each phase is operating equally.

Page 38

PCB TROUBLESHOOTING

Ranger 405D

The weld control circuitry has 2 modes of operation Constant

Current (CC) and Constant Voltage (CV).

In CC mode, feed back to the control circuitry is provided

by a 400 Amp to 50mV shunt, thus maintaining the

required set output current value. An Arc Force Control

operates when the weld voltage falls below a set value, a

factor of up to 2.5 times the current is progressively

applied.

The high Inductance -ve output stud is normally used.

ii. In CV mode, feed back to the control circuitry is provided by

sensing

the

output

required set output voltage value.

The low Inductance -ve output stud is normally used.

LED [L1] indicates an over current condition in the weld circuit.

The over-current sensor will time out to "phase back" the SCRs to

a pre set output current. This state is held until zero current is

sensed passing through the shunt.

LED [L2] indicates the latched state of the "phase back" circuitry.

LED [L3] indicates current flow sensed by the shunt. This "current

flow" signal is also optically isolated and sent to the Engine

Watcher/Idler PCB to initiate switching to " high idle" speed.

Reduced Open Circuit Voltage PCB

Constant Voltage (CV)

CV welding is unchanged. The wire feeder gun trigger, for units

with a control cable, initiates operation and for 'across the arc'

units eg LN-25 & LN-22 the 'Output Terminal Switch' must be

turned on. (ie the "I" position).

Constant Current (CC)

VRD CC welding has a reduced OCV (less than 8 volts). When a

resistance 20 ohms or less is sensed between the output studs

(ie striking the electrode to the job), the machine returns to normal

welding operation. While 20 amps or more is detected the

operation will be as standard. Less than 20 amps (ie breaking the

arc) the OCV returns to less than 8 volts after a maximum of 1

second. (The '20 Amp' signal is derived from the Rotor / Weld

Control PCB).

The 'Output Terminal Switch' is inoperative in CC mode.

Operation is the same in both high and low speed (Idler)

conditions.

Note: A fault in the machine, (eg short circuited SCR), that

causes more than 9 volts across the output terminals this VRD

will cause the engine to be shut down and the 'Welding Output

Failure' LED on the control panel will be illuminated.

Volt and Amp Module PCBs

These modules are powered from the pilot transformer and

shows Weld Voltage Output and Weld Amps Output.