TDS8000 DC calibrator adjustment procedure does not produce expected results

[Jwalling]

Hello all,

I've just replaced the dead NVRAM batteries on the ACQ board and the NLX processor board. I've re-programmed the NLX board via the serial port interface so now the scope boots up into the oscilloscope application OK. Signal path compensation for the mainframe passes OK, but the scope application reports an error 171 NVRAM data integrity. Not surprising since the cal constants for the ACQ board were lost due to the dead battery.

So, now I'm trying to run through the calibration procedure listed under the "adjustment procedures" in the service manual. This is where the problems start. I'm trying to do the DC calibrator adjust and I'm getting rather bizarre results. First off, the DC cal voltages with the default settings before calibration are pretty good - when I set the output to +1VDC the output is within 5mV or so. However when I go through the DC calibration procedure and save the results using the GPIB command CAL:SAVE:FACT:MAI and then SYST:PROT ON
the DC calibration output is completely screwed up! When I set the voltage output to be +1.0VDC, the output swings to -1.0VDC! 

At this point I went back and went through the procedure again, thinking I made a mistake somewhere, but got the same result. I've had a talk with a T&M dealer that I know pretty well and asked them if they've ever done this procedure in the service manual and they told me that they've had the same problem when attempting this procedure on a CSA8000 and had to resort to getting a professional calibration done (possibly Tektronix factory) to correct the problem.

I am beginning to think there is an error in the service manual. Has anyone ever successfully done this procedure or know where the error in the manual lies?
Perhaps there is an error in the formula on the third page of the procedure:

9. Enter the following GPIB command to set the instrument’s
calibrator to --1.0 V:
CALIBRATE:DCCALIBRATOR --1.0
Record the DMM reading (reading2).

Calculate cal constant as follows:
(–1.0 * Reading2 + Reading1)
________________________
                   2

10. Enter the following GPIB command to set the instrument’s
calibrator Lsb cal constant:
CALCOMP:DOUBLE “DcCalLsbAdj”,calculated result from Step 9.

Thanks for any help!

Jay

[leppie]

That -- (double dash) might be artefact from copying from Word.

Seen software devs get burnt with that many times. 

[AndyCandy]

This is to all who know the TDS8000 well.
Would you please provide the rest of us with precise instructions how to change the small 3 V batteries and how to program the lost memory in the instrument. It is my guess that this will apply to many TEK scopes.
Thank you.

[GastonBA]

Hello,

I am stuck in the same error place, the 171 error on the NVRAM. Anyone has been able to solve it and willing to share?

Thank you,

Gaston