I will show you some tips how to update firmware in Brother printers. You have to be sure that you have correct firmware file. If the headers are correct printer will flash no matter what do you send (i think so :). There is no checksum, only size control?

I will try to find how to enter service mode in this printer, the header should be a clue:

Flash file is the same that is downloaded by printer in web panel or with tool to upgrade on computer.

Flashing printer in network

Requirements:

  1. firmware file: LZ5094_L[1].djf
    http://www.mediafire.com/file/a3p9a5otccys6u9/LZ5094_L%5B1%5D.djf.zip
    Same file with changed extension to bin:
    http://www.mediafire.com/file/ibbelr09l6bmv1f/MFC-L2700DW.bin.zip
  2. BRAdmin Lite: 10/11/2016 (1.29.0000)
    http://support.brother.com/g/b/downloadend.aspx?c=us_ot&lang=en&prod=mfcl2700dw_us_eu_as&os=10013&dlid=dlf005040_000&flang=4&type3=284
    or BRAdmin Professional:
    http://support.brother.com/g/b/downloadend.aspx?c=us_ot&lang=en&prod=mfcl2700dw_us_eu_as&os=10013&dlid=dlf005042_000&flang=4&type3=26
  3. I have tested on EU versions printers, probably all firmwares are the same only mainboard has set regional settings in service menu.

Upgrade process:

  1. Download firmware and BRAadmin. Install BRAdmin.
  2. Connect your printer to network, turn it on. Do not send any printing,scan or other task.
  3. Rename .djf extension to .dat or .bin or any other. If you do not do that, BRAdmin won’t accept the file:
  4. Run BRAdmin. Right click on you printer and click Send file and choose .dat or .bin file:
  5. Wait for complete:
  6. Now on your printer LCD you should see

    Firmware Upgrade

  7. Wait about 20 minutes to printer finish the process (copy,scan,fax LEDs will blinking)

Flashing printer at USB

Sorry, I will try it later because I do not have USB connected printer. But BRPrint Auditor should make possible to see USB connected printer in BRAdmin:
http://support.brother.com/g/s/id/common_download/en/auditor_pro3.html?c=us_ot&lang=en&redirect=on