TDS784C-FAS Stack on "MEMORY WRITE PROTECT SWITCH" after aborted Volt. Ref. Cal. - Page 1
Forum section: electronics / testgear

author: micaticu
author_rank: Contributor
timestamp: April 15, 2022, 10:01:23 pm
content: Hello everyone,First I will mention in short the present situation of my problem for those of you who may have already encounter this problem and may have the answer right away.My TDS784C seems to be fully operational at present but I can not recalibrate it. I will explain later why I whish to calibrate it.The Field Adjustment Software (started with ADJ700C.BAT) is communicating with the instrument and functioning normally up to the point where it prompts "MEMORY WRITE PROTECT SWITCH" asking to put the switch in unprotect mode. Of course I tried to change the switch position but to no avail. The software is not passing over this message, prompting it again and again no matter in what position the switch is.I have been able to read/ write and verify the DS1650Y and DS1486 nvrams without problems trough the GPIB, using the Unified Tektool. I have also been able to try a clean version of firmware v5.3e and also v5.2e, using the same software (the scope came with v5.3e installed and functioning).And to conclude the short presentation of the problem I have to mention that when I check on the scope the status of the current calibration, under UTILITY, I have the following results:-SIGNAL PATH - Pass (and it passes every time I run it)-VOLTAGE REFERENCE - Running-FREQUENCY RESPONCE - Initialized-PULSE TRIGGER - Initialized-COMM FILTERS - Not presentAnd now, the longer explanation of how and why I am in this situation, and more details on my setup and what I have tried so far.I have purchased this scope about six or seven years ago, fully calibrated and running. Reading extensively on this and other forums about the danger of losing the content of the nvrams, I have decided to acquire some tools to save their content and to be able to recalibrate the unit if necessary.My setup:-PC running DOS 6.22 plus a GPYB-PCII/IIA card and FAS 700C and 700D installed and running.-Data Precision 8200 voltage/current source with GPIB-HP8664A 3GHz signal generator with GPIB (but used in manual mode for calibration)Upon reception and verification of the scope, I noticed a slight dip in frequency response around 600-700MHz and I decided to recalibrate.I found and installed the Tektronix TDS700C Field Adjustment Software and started the calibration. I have done this a few years ago and I remember that it did not go very smoothly; I think because of a communication problem with the Data Precision 8200, so after many tries, I decided to try the version ADJ700D (instead of ADJ700C) of the FAS and that went better. I have even succeeded to automate the first part of the calibration (VOLTAGE REFERENCE) up to the very end where the FAS stopped short of saving the calibration. I have tried also to run the FREQUENCY RESPONCE calibration only, but unable to finish it. I have aborted and restarted the FAS from the very beginning a few times until, after having reached the same point as previously mentioned, system got stack, unresponsive, and I had to power off the PC.From that point on, restarting the FAS, I have never past the "MEMORY WRITE PROTECT SWITCH" prompt even if the scope continues to run normally otherwise, but with the VOLTAGE REFFERENCE, FREQUENCY RESPONCE and PULSE TRIGGER stuck in the states mentioned above.All this happened a few years ago when I received the scope, but I continued to work with the scope anyway, as it otherwise seamed to work ok, having kept the original calibration intact.A few weeks ago I decided to revisit the situation, and I have looked what is new on the forums related to my problem. Some very creative and talented people have developed tools (new to me), like Tektool or Tekfwtool to communicate with the scope trough the GPIB port or to use the floppy as a backup device. I have used Unified Tektool and I successfully saved and rewritten the NVRAMs and firmware contents.But I am still unable to make the FAS advance over the "MEMORY WRITE PROTECT SWITCH" prompt.Trough many hours of research trough the forums I have found a single mention of my situation being possibly due to some corrupt eprom. In this YouTobe, --><--, at 7:27min, "tekhobbycap" mentions that you can get "stuck on 'RUNNING' " as I am with my VOLTAGE REFERENCE calibration but without developing on the subject.I apologize for the length of this post, but I tried to give as much details as I could regarding my problem.Any suggestions or advise would be greatly appreciatedThanks