@USER@555 pointed me here:
ZTE MC801 / MC801а – обсуждение, [ltemodem, 3gmodem, wifirouter] : ~ 1,2 Гбит/секMb\s - ~ 2,4 Гбит/секMb\s + 2x1Gb | Нет
4pda.to
My router was bricked and the com port wasn't visible via USB,
It was therefore necessary to disassemble it to get at the test point contacts.
Disassembly was as follows:
Remove rubber footing and unscrew 6 screws in the base.
Prise off the top vent and unscrew 4 screws.
Prise off the strip surrounding Ethernet and antenna ports.
Pull off the outer case
Unscrew four screws holding the large heatsink. Note, the 5G antenna sits on top of this heatsink and removing it will unplug the antenna wire. It will need to be snapped back in place when reassembling.
I followed the above instructions on the Russian site. I have copied English translation below.
1 connect the USB data cable to the router
2 transfer the folder with firmware to the path C:\Program Files (x86)\Qualcomm\QPST\bin
3 shorten the name of the folder with the firmware as much as possible - for example, call the folder just the number "1", no characters, cyrillic, etc.
4 prepare the QFIL in advance and fill in all the necessary files from the new transferred folder (folder number 3 in the firmware)
5 port selection in QFIL is untouchable! the port should be determined in the QFIL as a result of the following actions (this is critically important)
7 Disassemble the router according to the step-by-step instructions (PDF file) that you will find at the end of the post (it's easy)
8 Keep device manager on the computer open
9 Remove the power cable from the router
10 close both contacts with tweezers at the same time as shown on the TEST POINT screen:
11 Insert the power cord into the router and only after a few seconds remove the tweezers from the test point
12 in the device manager will quickly appear a device QUSB_BULK almost like with a regular brick, but the name this time will be longer, as on the screenshot:
13 now act quickly - click in the manager "update hardware configuration", the device should ITSELF be picked up by the wood pre-installed on the computer for the 9008 mode and enter this mode, respectively in the QFIL - the port at the top should appear ALSO ITSELF at this stage. as soon as port 9008 appeared in QFIL - instantly press the DOWNLOAD button and see that the firmware of the router - has begun.
14 we are waiting for the end of the firmware, if we see everything as on the screen below - congratulations, you were to restore a complex brick.
This didn't work. I did manage to get com port 9008 active but the flash erase step failed.
@USER@555 offered to fix it. I needed to install Telegram and Teamviewer.
After about an hour of connected work the router is now working again.
He offered his paypal address and I sent him a small sum.
There was a bit of difficulty with resetting the login password but with 555's help it was resolved.
Sotel has just informed me by email that they have dispatched a replacement MC801A. Hohum... I may just keep it as our friend didn't leave instructions on how to fix it again.