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Observe all Safety Guidelines detailed throughout this manual
PC BOARD TROUBLESHOOTING
GUIDE - CONTROL P.C. BOARD
1. The white Power light on the machine control panel
indicates that the Control board power supply is
being supplied by rectified secondary voltage from
the Control transformer (T2) by way of the Power
switch and transformer iron rear thermostat.
2. LED1 indicates machine output voltage. At normal
output voltages, LED1 will be brightly lit.
3. LED2 indicates the level of the control signal to the
Firing board. The brightness of LED2 is inversely
proportional to machine output because the control
signal increases as the machine output decreases.
4. LED3 lights when the current amplifier senses an
output current over about 10 amps and sends a sig-
nal to turn the cooling fan on. If LED3 is on but the
fan is not , there could be a problem with the fan
motor or the fan motor drive circuit (see LED6).
5. LED4 says that some signal, either thermostat, out-
put current or output over-current is calling for the
fan to operate.
6. LED5 tells us that the current signal from the shunt
is too high. If LED5 is lit for 5-8 seconds, the enable
signal to the Firing board is made high to shut off
the output SCRs. In the case of a short duration
current overload, LED5 may only be briefly lit
because, in normal operation, the machine output
immediately goes to zero. Once disabled, the out-
put will remain off for about 75 seconds.
If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact your
Local Lincoln Authorized Field Service Facility for technical troubleshooting assistance before you proceed.
TROUBLESHOOTING
7. LED6 indicates that the input to the fan motor opto
triac driver has been energized. LED6 should be on
as long as the fan motor runs. LED6 and the fan
motor will be on for about 5 minutes after LED4
goes off.
8. LED7 will light when the shorted SCR circuit acti-
vates. A positive voltage on the negative output
stud (AC instead of DC on the output studs) will
activate a circuit causing the input contactor to
open. This circuit is active only when the enable
signal to the Firing board is high (the output is off).
The contactor will remain open (and the white
Power light will remain on) until the Power switch is
turned off (or the input power to the machine is oth-
erwise removed) for about 1 second and then
turned on again.
9. The green Safe Output light on the control panel
when the machine output voltage is present and
safe. It lights when the machine output is between
40 Vdc and 113 volts peak.
10. The yellow Thermal light on the front panel lights
when the open thermostat signal is sent to the fan
control and output disable circuits.
CAUTION
MULTI-SOURCE
E-5
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