[volt-nuts] Datron 1281 NVRAM woes

[Bert K]

Hello,

all of a sudden my beloved Datron 1281 stopped working.
If briefly displays the familiar 
"DCV: Auto 100mV......"
but then
"Secondary NV C/SUM ERROR 2101"
and then 
"9005.7 No Rtx    001B42"

The voltages from the DC board PS seem okay, also the
battery displays only a bit less than 3.7Vol.

Obviously I wonder whether anything can be done here.
In particular I wonder about the NVRAM setup,
namely whether "Secondary" could be just a safety copy
of the "Primary". Or whether this is the less important
set of self-cal constants, etc.
I couldn't find any info in the various manuals. 


Also the second error seems to have to do with
serial comm, and it is not evident that is has anything
to do with with the first error. If not, then they could have
a common underlying reason, like a faulty PS.

The PS of the digital board is different than as the one
described in the manual, so I can't really check the voltages
meaningfully. Does anybode have schematics of this
second (I hear common) type of digital board?
Or knows otherwise what the voltages on the various 
test points are supposed to be?

Thanks,
Bert