Diagnostic Testing and Troubleshooting
Analog Troubleshooting
5
5-13
Note
When making voltage measurements in the inverter circuit, remember that
there are two separate grounds. The out-guard ground is the ’GRD’ test
point, and the in-guard ground or common is the ’common’ test point.
The normal input current to the inverter supply is about 210 mA, or 1.05 V across
A1R46.
5-9. Analog Troubleshooting
Analog circuit problems are evidenced by Error 8 or Error 9 in the display. These errors
signify either that the Main Processor (A1U6) is not communicating with the in-guard
circuitry or that the Analog Measurement Processor (A1U1) is not functioning correctly.
First, check the in-guard power supplies referenced to common:
Power Supply Testpoint Range
VDD A1TP10 4.95 to 5.45 V dc
VSS A1TP12 -4.95 to -5.45 V dc
+VAC +VAC +4.7 to +5.35
-VAC -VAC -4.7 to -5.35
Check the out-guard to in-guard communication for activity whenever a front panel
button is pressed. If necessary, press a button repeatedly while looking for the following
communication activity:
A1TP8 = GROUND to VCC pulses
A1TP4 = COMMON to VDD pulses
Check the in-guard to out-guard communication:
A1TP5 = VDD to 0.7 V above COMMON pulses
A1TP7 = GROUND to VCC pulses
Check the crystal oscillator referenced to COMMON:
A1TP3 = a 3.84 MHz sine wave (260 ns period)
Check the integrator waveform referenced to COMMON:
A1U1-45 should be a triangle wave when an input is being measured.
Check the 1.1 V reference:
A1TP2 to A1TP1 = +1.1 V
In general, check that the relays are getting the proper drive signals and that they are in
the correct position.
The 10 A current shunt (A1R3) or the mA current shunt (A1R2) can be used as a
convenient COMMON test point.
5-10. Uart Test
This test checks both the optoisolators (A1U3 and A1U4) and the Analog Measurement
Processor (A1U1) UART circuitry. The Main Processor (A1U6) first sends a break
signal (5 V dc, logic high) to A1U1, then waits for a break signal in response from
A1U1. Once this occurs, A1U6 commands A1U1 to remove its break signal response.
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