I'm trying to patch strings in my firmware with a hex editor but I keep getting a checksum error when I go to re-flash the modded firmware onto my device. The device is a Roland gr-55 guitar synthesizer and here is a link to the firmware. Firmware download
So I run binwalk on the gr55.bin file and it tells me it's compressed with lha compression. So when I decompress it, it gives me appli.bin file. From there I open appli.bin with a hex editor and change the names of a couple strings. This is where I'm lost, I orignally just tried to re-compress the appli.bin file with lha compression and flash it to my device but nothing happens. I've tried using Firmware-mod-kit but it says my file is unsupported. I changed a few bytes in the compressed gr55.bin file and tried to flash it to see what happens and my device displayed the words checksum error.
The tutorials I have watched where they patch binaries they disassemble the firmware, find where the checksum function is and disable it. I don't have the cpu of my device yet so I'm unable to disassemble the firmware. All the forms and tutorials I found, where they rebuild firmware images seem to show examples of routers which have squashfs file systems and seems different from what I'm dealing with.
So I don't know how to properly rebuild my firmware image so when I go to re-flash I don't get a checksum error. Can somebody please help or point me in the right direction.