Denon AVR-4520CI Service Manual page 74

(2) When DSP STAY is removed, put some shock absorbing material there so that the DSP board (8U-310115) does not come in
contact with the digital board (8U-310116). To verify the element under the DSP board through an oscilloscope, etc., remove the
DSP board, pull out the lead, and reinstall the DSP board before verification.
When the set is turned on without installing the DSP board, the SUB microcomputer does not function properly.
Insulation sheet
(3) PCB HDMI is detached from the chassis, and it puts it into the state turned inside out.
Please pave an insulation sheet that is larger than PCB HDMI under PCB.
Connect the ground point of PCB to the chassis with a ground lead or the like.
Connect the four extension jig cables.
Insulation sheet
Ground lead
(HDMI connector to Bakpanel chassis)
74
DIGITAL UNIT
(8U-310116)
Extension JIG cables