Specifications

SECTION 5 MACHINE TESTING / TROUBLESHOOTING / SERVICE

5.11.1 PC650 Fault Monitoring

Over/Under voltage fault—Flashes 5 times per second.

Over voltage--This condition is the only one that will activate before the torch switch is closed. The PCB1

Control board has a voltage monitoring circuit and major fault logic built onto it. IC3 is a voltage com-

parator circuit, which monitors the unregulated voltage that feeds the positive 12 and 15 volt supplies. If

the voltage dips below 11.8VDC IC3 sends an error signal to IC2 pin 4 and this signal sets the fault on IC2

pin 12 turning on Q5 and Q6. This turns on the under voltage/over voltage fault LED on the front panel.

Under voltage-- From the same unregulated reference point on the positive 12 and 15-volt bias supplies,

the over voltage sense circuit is monitored. This involves the voltage being input on IC2 pin 17 where it

is monitored and when it reaches 25VDC this will set the fault on IC2 pin 12 turning on Q5 and Q6. This

turns on the under voltage/over voltage fault LED on the front panel.

Thermal Fault—LED is “Mostly On” --This circuit is activated when an open thermal switch is present

when the trigger switch is closed. The thermal switch fault will generate a ashing light on the fault light

on the front panel. This light is described as mostly on. Mostly on is when the LED is on for 9/10 of a sec-

ond and o for 1/10.

Flow Fault—LED is Mostly O-- This circuit is activated when an open ow switch is present when the

trigger switch is closed. The Flow switch will generate a ashing light on the fault light on the front panel.

This light is described as mostly o. Mostly o is when the LED is o for 9/10 of a second and on for 1/10.

Over Current Fault—LED is on solid

Lastly, PCB1 monitors the current in the main transformer (T1) primary, in the event of a major fault,

current in the primary will increase and at 100 amps a 1-volt AC signal is generated and supplied to pins,

P1-7 and P1-8. This voltage is rectied and fed to IC3 where a “Limit” signal is created and transferred to

IC2. IC2 will create an over current fault and will turn on the fault by setting IC2 pin 12 high and turning

on Q5 and Q6. This turns on the under voltage/over voltage fault LED on the front panel. This shows on

the front panel as a steady light.

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