Marantz NR1504 /U1B Service Manual page 52

(3) When connection is good, then you can see the "Communication check OK." message.
(4) If connection is not good, then you can see the "Communication check NG" message.
Please confirm the following
(a) Check the connection of the AV receiver and PC. (refer to "1.2. Connection of the AV receiver" )
(b) Check the operation mode of the AV receiver. (refer to "1.3.Turn on the AV receiver")
(c) Check the selection of the RS-232C port number of PC.
1.6. Download the firmware
(1) Click the "Load" button.
(2) Download the firmware from the specified download source to PC.
XXX-XXXX
XXX-XXXX_WWWXXXXYYYY-ZZZZ.bin
XXX-XXXX_WWWXXXXYYYY-ZZZZ.bin
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