Maintenance
760A / 760D / 760N 4–7
PIN 18 DELAY makes a low–to–high transition when the current signal value
is ≥ the stored peak value. This clocks the current value into the peak
value latch and starts the peak–hold time–out circuit.
PIN 19 BAR ENABLE goes low when a segment should be lit.
The following pins are internal nodes without external connection.
PIN 13 LCMP is a delayed and inverted CMP signal.
PIN 14 PEAK goes high when the first peak segment should be turned on.
PIN 15 DPEAK goes high when the second peak segment should be turned on.
PIN 16 S, S and CLEAR (PIN 17); are state variables for a state machine that
looks for the low–to–high transition of TIMEOUT.
Power Supply Troubleshooting Procedure
NOTE. A review of the power supply theory of operation is recommended before
attempting repairs.
The equipment needed to troubleshoot the power supply:
HDigital Multimeter (DMM), with a diode check function
HOscilloscope
H0 to 20 VDC Variable Power Supply
HClip Lead – to short across a component
HHigh Voltage Probe, w1 GW input resistance
The Troubleshooting Procedure for the Power Supply (Assembly A1) is split into
two sections, the Low Volts and High Volts Supplies. Start the procedure by
determining which section of the power supply the problem is in. Apply AC
power and turn on the power supply. From Table 4–1, determine which
symptom the power supply exhibits and refer to the corresponding procedure.
Introduction