Pvlk Taras

Hello folks.
I bought a Tektronix TDS 820 for repair.
The main screen is dark, but the segment indicator on the motherboard runs.
After connecting to the debug console port, I have the following log:
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Int V
   Bootrom Header Checksum passed.
   Bootrom Total Checksum passed.
   BootRom Check Sum passed.
   Bus Error Timeout test passed.
Kernel Diagnostics Complete.

Calling SDM (monitor) Routine.
   Enabling Bus Control register. Value = 0x67
   IMR 1 Register test passed.
   Misc. Register test passed.
   Timer Interrupt test (Auto-Vector) passed.
NVRam DSACK FAILED, wrote 0x12345678, read 0x78ffffff

NVRam DSACKS test failed.
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Also I replaces DS1245Y to new one but the result still the same.

I am also interested in whether it is necessary to flash the DS1245Y memory after replacement to new one.
What exactly firmware need to upload in the DS1245Y memory?

Also on eBay i found diskettes for my oscilloscope model...
I'm curious about the left one on the photo(attached).... what does the "Оptions key" mean?

Thanks!