I successfully updated the firmware on my older version TDS784C from 5.0a to 5.2e, using an ebay sourced Keysight 82357B USB-GPIB adapter.
Here's the full instructions on how I did it, combining info from madao and rodd.
1.) Install Keysight IO Controls and set settings as shown in the included images.
(This is important to allow tektools utility to access the GPIB adapter!)2.) Run IO Controls (Icon should appear in task bar) and run Keysight Connection Expert.
3.) Plug 82357B USB-GPIB adapter into PC and scope. Turn hidden switch in scope to unprotected mode and turn on scope.
4.) Check for the scope appearing in Keysight Connection Expert as shown in the included image.
5.) Open Command Prompt and navigate to folder containing tektool.exe
6.) Type in the following commands shown in quotes (don't type the quote marks).
7.) Identify flash type "tektool -i -b 0x1000000 -l 0x10"
8.) Save existing NVSRAM (not for TDS400 series, unknown address) "tektool -r NVSRAMSave.bin -b 0x4000000 -l 0x100000"
9.) Save old firmware "tektool -r example.bin -b 0x1000000 -l 0x400000" (28F010 = 0x180000, 28F020 = 0x300000 instead of 0x400000)
(example.bin = name of existing firmware file)
10.) Fill zero to flash (only for old flash 28F010 and 28F020) "tektool -z -b 0x1000000 -l 0x10"
11.) Clear firmware "tektool -e -b 0x1000000 -l 0x10"
12.) Flash new firmware "tektool -p example.bin -b 0x1000000 -l 0x400000" (28F010 = 0x180000, 28F020 = 0x300000 instead of 0x400000)
(example.bin = name of new firmware file)
This will take a while. On a TDS784C, it took just under 45 minutes or so.
13.) Writing NVSRAM back into memory (optional, not for TDS400 series, unknown address) "tektool -w NVSRAMSave.bin -b 0x4000000 -l 0x100000"
14.) IMPORTANT: Power cycle unit before verification of firmware. Wait 10 seconds after power-on, then switch protect-switch to "protect" for safe verification.
15.) Verification of firmware "tektool -v example.bin -b 0x1000000 -l 0x400000" (28F010= 0x180000, 28F020 = 0x300000 instead of 0x400000)
(example.bin = name of newly flashed firmware file)
16.) Reboot scope, enjoy.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
16a.) I did a factory reset on my scope for good measure, just to make sure there were no incompatible settings etc from the old firmware to the new firmware.