Denon AVR-X2300W Service Manual page 103

Checking the reset waveform.
Check item(55). Checking the reset :
Check the CPU.
Is the waveform of the TP near the GUI(U1026) correct (like the one
shown in the diagram) when the power is turned on?
YES NO
Check the reset circuit between CPU (U1018) and GUI (U1026).
If there is no problem, the GUI (U1026) is faulty.
Replace with a new device.
Recheck from check item (1).
If it does not work, replace the PCB.
Check the I2C communication line.
Check item(56).
Check the CPU.
10ms
Is the "I2C" waveform of the TP near the CPU(U1018) correct (like
the one shown in the diagram) when the power is turned on?
10ms 10ms
Example of the waveform to be checked
YES
The GUI (U1026) is faulty.
Replace with a new device.
103
YES
Check the I2C communication line :
NO
Check item(57). Check the I2C communication line :
Check GUI (U1026), HDMI SW(U1103) and CPU(U1018) patterns as well as soldering.
If there is no problem, go to the next step.
Check the CPU.
Remove the damping resistor (R1493/R1494)
of (U1018).
Is the "I2C" waveform correct?
YES
The GUI (U1026) is faulty.
Replace with a new device.
*The diagram shows an example.
(Signal patterns vary depending on the
timing.)
Points for checking waveforms
- Crest value (3.3 V normally)
- Signal change
- SCL frequency (400 kHz normally )
The CPU(U1018) is faulty. Replace with a new
NO
device.