ADS1013D Oscilloscope

[kenparkyn]

Hi.
I bought the above about 18 months ago and all worked fine.
Just now powered it up and everything works except there is no displays of signal on either channel.
It's registering 1KHz at 3.5V p-p using the probe calibrator but I see nothing.
(Yes, I've switched it off and on again.)
Aliexpress where I bought it say its out of warranty so no help there.
Bin job? or is there a service manual.? Any tricks I'm not aware of?
Thanks
Ken

[tunk]

I guess this is the same as the Fnirsi 1013d.
This has a long thread, and I think the eevblog user "pcprogrammer"
did a reverse engineer and alternative firmware:
https://www.eevblog.com/forum/testgear/fnirsi-1013d-100mhz-tablet-oscilloscope/

Edit: Here a link to pcprogrammer's firmware page:
https://github.com/pecostm32/FNIRSI_1013D_Firmware

[Grandchuck]

Sounds like the analog front end is working since the calibrator frequency is displayed.  I see why tunk mentions firmware.  But, why would the firmware have been corrupted?  Do you have any ideas about how that could have happened?