Re: 2467B TEST 04 FAIL 02

Chuck Harris <cfharris@...>

Sadly, there is no sanctioned way of telling what step
has failed.

You can tell with unsanctioned methods by reading the
NVRAM, and looking at the data bits. The location and
layout of the calibration data is only loosely described
in the maintenance section of the manual. There are 170
14 bit calibration constants in the NVRAM. Each of those
constants has its own checksum, and status bits to tell
if it is in or out of range. All left to us as a mystery
by tektronix.

If you look at the calibration data using the EXER02 function
in the calibration/test menu, you will see each of the
256 RAM locations you can read has the format:

AA DDDD P, where "AA" is the address, "DDDD" is the hex
data for the constant, of which 14 bits are valid, and P is
the parity bit X is even, blank is odd.

The actual locations of this data in the NVRAM have been
found and discussed by others on this group.

I meant one day to take a virgin NVRAM, and read it after
every step of the calibration routine is completed, and
to note the differences in the calibration section of the
NVRAM. I will probably never do so, because I, well, I have
a life, and I just don't care that much....

However, there is nothing stopping one of you from doing
the heavy lifting. I would suggest using what is called
an EPROM emulator, or RAM emulator to save wear on the
NVRAM socket. There will be at least 170 times the data
after a calibration step needs to be compared with the
"virgin" NVRAM data.

Please note that the NVRAM has only 170 calibration constants,
and the entire rest of the NVRAM is used as program storage,
and as a result, is reset every time you fire up the scope.

This is your task should you choose to accept it, good luck
with it! International fame and no fortune await!

-Chuck Harris wrote:

My 2467B >B052xxx suffered two nasties! (The processor board caps exploded and subsequently ate up some of the copper traces near them underneath the solder mask layer. (tough to see)
Also my sram backup died. I was able to get a new recent date code SRAM and it works ok but no cal data now. Also I was able to clean up the cap mess and replace the crummy electrolytic caps with tantalum caps.
I went thru the tek "ADJUSTMENT PROCEDURE" and set everything I could: the really fast horizontal cal's I didn't have gear for. I approximated the top end and pressed the trigger coupling button. I was able to program everything else, or so I thought, but now I am getting a cal limit error TEST 04 FAIL 02. Since the procedure is quite lengthy, with a lot of steps stored, it would be great to know which step of which cal is out of limit.

Is there a way to determine which cal/step is responsible for the error?

All responses are welcome, Thanks

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