TDS5054 calibration problem

[andy2000]

I'm trying to resurrect this Tektronix TDS5054 oscilloscope.  I'm almost there, but there are a couple of nagging problems. 

First, it first starts up, I get a message saying "CAL: failed to read NVram, will use uncalibrated factory defaults.  The scope must be calibrated at the factory". 

Second, although it passes SPC, it forgets that it has passed.  The SPC status goes from "Pass" to Initialized" shortly after running.  Even thought it says "initialized", I know it's using the SPC values since the DC offset is still good.  Before running SPC for the very first time after on OS restore, it has lots of DC offset.  Could this be related to the CAL failure?

Otherwise, the scope seems to be working fine on all channels, and passes the self test.  Calibration seems reasonably close.

I'm running a fresh OS, so I know it's not a software problem. 

From the service manual, I know the cal constants are stored on the acquisition board (or possibly the processor board), and SPC on the hard drive.  I can only find one EEPROM on the acquisition board (U1800), and it does contain data.  I can see the scope's serial number in plain text, so I know it has at least some valid data in it.  The serial number and options are also being picked up properly.  The scope application won't run if I remove U1800, so I know it's accessing it.

I have found none of those battery backed up Dallas NVRAMs, so I don't think it's a dead battery.  Does anyone know for sure where the CAL data is stored?

The service manual says you can do a calibration with some simple GPIB commands, but it assumes you have a very specific set of test equipment.  Is there a way for me to attempt a rough calibration just to see if it will even clear the error? 

Asking for the calibration status over GPIB returns the following:

:CALIBRATE:INTERNAL:STATUS INIT;
:CALIBRATE:TEMPERATURE 31;
FACTORY:FANCONTROL 2;
STATUS UNCAL;
STEPSTATUS FAIL;
STEPSTIMULUS "0.0,0,0,0,END";
NOTIFY:HOURS 10500;YEARS 5.5000;
DUE DUE;
:CALIBRATE:RESULTS:SPC INIT;
FACTORY UNCAL;
FACTORY:VOLTAGE INIT;
FREQUENCY INIT;
TRIGGER INIT;
:CALIBRATE:PROBESTATE:CH1 1;CH2 1;CH3 1;CH4 1


Thanks in advance,

Andy

[andy2000]

It looks like the cal constants are stored in U1800 on the acquisition board:

www.tek.com/dl/TDS5000B_MemoryErasure.pdf

[calibrationfixture]

Hi,

Thought my problem was unique, but Google leads me to yours.

My Post:

https://www.eevblog.com/forum/repair/tds5104-cant-find-cal-data-during-starting-scope-application/msg4586218/#msg4586218

With some additional details.

Did you find a solution? My Scope is also nearly perfect "calibrated", but Probe Cal is cumbersome, because after little time you must run SPC again (SPC Status has gone from Pass to Initialized).

I haven't done the PPC Reset and ordered new Xicor X24C16's (U1800). Cloned HDD, ChkDsk (all fine, no bads) and de/reinstalled Scope Application V 1.2.1. No changes.

Thank you for any assistance in this,

Calibrationfixture