I have an update.
After working with the new unit for a time, I decided to check the NVRAM of this module also.
The chip's datacode was 9705, so very old.
I decided to desolder this chip and read it carefully, paying extra attention to ESD.
It worked!
I could read the contents succesfully.
But the strangest thing is that the new chip, with a fresh datecode of 2017, doesn't do the job.
The analyzer fails @ the NVRAM check....
So, I thought I had ruined the thing for a 2nd time.... But when Installed back the original chip, it worked again!
I repeated this 3 times and it is consistent.
So, the module works OK with the original chip, but fails with the new copy.
And the contents are the same! I checked this with my eprom programmer. They are identical.
The original chip is the DS1225AD-85 and the new replacement is the DS1225AD-85+.
The '+' means only RoHs compatible...So, it should be OK.
What the heck!
Now I am thinking: Did Tektronix use special "best parts"from their suppliers? And that the access time is faster than the spec (85 ns) and that it operated close to/beyond the speed spec??
Should I buy a faster ( 70ns) chip to test?