Tektronix TDS644A failed NVSRAM Backup - Page 1
Forum section: electronics / repair

author: toby_muc
author_rank: Newbie
timestamp: January 20, 2018, 03:27:30 pm
content: Hi everyone,as this is my first post on the forum let me quickly introduce myself! My name is Toby, I am from Munich in Germany and although I studied electrical engineering back in the day I do electronics only as a hobby. I stumbled across EEVBlog on Youtube a few months ago and really enjoy watching the videos and reading through the forum. I even started to build a power supply for the first timeBut I have one problem I really could need help with:A couple of years back I got hold of a Tektronix TDS644A DSO which is (at least it was until I screwed things up) in good working order. After opening it up I found the backery-backed NVSRAM and decided to do a backup as recommended somwhere on this forum, as it certainly had reached it's shelf life some 15 years ago. I unsoldered the DS1650Y, copied it's contents and put it back into the scope. Should have been an easy task, but now the scope shows two errors right after start-up:- FAIL ++ Processor- FAIL ++ Cal initialization (see error log)After clearing this messages the scope does work, but shows quite a large voltage offset, about 50mV on the 100mV range with different offsets on the different range settings.No comes the funny part: I can't get into the error log, because to get there, I have to move the selection in the Utility menu accros "Cal". And there I get a lot of "bing" sounds and the attached error message. The signal path compensation, which might solve my problem, is also hidden behind this error message, so I can't do that either.Does anyone of you have an idea what went wrong?Thanks for your help!Regards,Toby.

author: andy2000
author_rank: Frequent Contributor
timestamp: January 21, 2018, 05:30:19 pm
content: Have you tried the secure erase option? That will reset everything to the defaults, and might clear the conflict.

author: seronday
author_rank: Regular Contributor
timestamp: January 21, 2018, 11:31:27 pm
content: The NVRAM has been corrupted.This exact same thing happened to me with a TDS524A after de-soldering and doing a read of the NVRAM contents.There is some information on this subject on a TEK forumhttps://forum.tek.com/viewtopic.php?f=568&t=135169&p=271724&hilit=%3A+TDS540+NVRAM+error+DS1245#p271713If you do a search for TDS5xx, TDS6xx NVRAM problems you will find quite a bit of info.Some people have successfully removed the NVRAM, copied it and put it back in. Other people have had the problem of corrupted NVRAM contents.Regards.

author: toby_muc
author_rank: Newbie
timestamp: February 04, 2018, 11:37:21 am
content: Thanks, I'll head over to the Tek-forumI shouldn't have touched it ...Regards

author: Armadillo
author_rank: Super Contributor
timestamp: February 04, 2018, 12:42:51 pm
content: You would need to determine whether your desoldering job was a good job or very badly done?Cause you may have broken the vias or tracks or caused heat IC damage.?Desolder it out, repair the vias or tracks or replace the nvsram.But I don't think the desoldering was that hard for this board.

author: Kecaptraitim
author_rank: Newbie
timestamp: May 23, 2025, 04:26:21 pm
content: hello im facing the same problem with my tektronix tds524a, did you solved it ?

author: CaptDon
author_rank: Super Contributor
timestamp: May 23, 2025, 07:39:09 pm
content: You should never desolder a low battery NVRAM and try to read it. Always use the TEKTOOL posted on this forum to make a floppy disk copy of the data from your 'working' scope before you butcher the data and corrupt it. Once you unsolder the chip and handle it you almost assuredly corrupt the data. I believe I have both the 644A and 644B NVRAM data files. I will try to post them to this thread. I hope I can post a 512KB file as I think that is the size. If I recall there may be two files I have to post?

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 24, 2025, 01:09:40 am
content: You can post a few megabytes per post, no worries. (Just don't use the first attachment upload slot, there's a forum bug. Click to add more attachments and use from the second slot).Best bet is to use the tektool to dump the firmware and NVRAM and zip them together per scope, and name the file with scope model and firmware revision.I have TDS600 series firmware and NVRAM dumps too which might be the correct model type but I'm always looking for more, but I don't have any from a TDS524A.. @Armadillo, can you make a firmware and NVRAM dump via GPIB?

author: Kecaptraitim
author_rank: Newbie
timestamp: May 24, 2025, 03:24:41 am
content: This is my first scope btw, if the nvram is corrupted is the anything i can do to fix it? i dont have any cable that can connect the oscilloscope to my pc :'(

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 24, 2025, 07:36:43 am
content: You can replace your NVRAM with this, and never have to worry about NVRAM's again...He can pre-load the firmware and NVRAM for you too, so it's a simple swap. I've used them in three scopes so far and they work perfectly.https://www.ebay.com/itm/302913384290

author: Kecaptraitim
author_rank: Newbie
timestamp: May 24, 2025, 09:32:11 am
content: woah expensive :'(

author: CaptDon
author_rank: Super Contributor
timestamp: May 24, 2025, 02:03:13 pm
content: Read up on the forum about making a 'restore' floppy disk. I bought the Ebay replacements for both the 644B I still own as well as the 644A that I sold. They are worth the money indeed!! My 644A only needed one NVRAM/RTC combined I.C. If I recall the 644B required 2 I.C.'s I bought the set for the 644B first and was impressed. The Ebay seller agreed to sell me the single I.C. for the 644A at a lower price. It has been a few years but I believe I did both the backup and the restore process strictly by floppy only although I seem to recall you need to flip one or two of the DIP switches to allow you to do this.

author: Kecaptraitim
author_rank: Newbie
timestamp: May 24, 2025, 02:57:15 pm
content: Thank you for your advice, but i think i will not spend $140 for 2 ics, i paid $140 for the scope. Have a wonderful day!

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 25, 2025, 09:50:25 am
content: If you search around, you can find details on cutting the NVRAM chips open to replace the batteries inside.It's not tooooo difficult, especially with access to a mill, or some time with a file and a vise....

author: madao
author_rank: Frequent Contributor
timestamp: May 25, 2025, 03:02:16 pm
content: If someone make DS1486 replica, then would said: good price (no joke, i have high frustration with DS1486 replica)Buying DS1486 from China, with faked data code and replace battery. This is a good solution (for me)OR: DS1245 and foregone about working clock.

author: CaptDon
author_rank: Super Contributor
timestamp: May 28, 2025, 11:01:57 am
content: Are you wanting my TDS644A capture file from a working unit? I believe it also has the FFT function enabled. I think the file is 512K. I also have the associated .bat file.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 28, 2025, 12:52:05 pm
content: Are you asking me?If so, I wouldn't mind a copy of the firmware and NVRAM if you can extract it.

author: CaptDon
author_rank: Super Contributor
timestamp: May 28, 2025, 10:09:52 pm
content: Please let me know if this ZIP file successfully creates dump1.bin and dump2.bin I believe both files are identical, I simply saved the data twice as a safety. It is the contents of the single 512K NVRAM. If the files don't compare it will be in the first 16 bytes where the real time clock resides. The files came from a fully functioning TDS644A. I am guessing you will have to run a Signal Path Calibration routine since my SPC values will almost surely be different than yours. As I recall this scope had the FFT functions enabled when bought new so you should also have that function available when loading this NVRAM data. Please do read the tektool information on this forum!!! I believe this data can be loaded via floppy disk. DO NOT edit the data!!!!!! I found when opening the file under certain viewers it causes some sort of corruption to the file and the tektool won't be able to load it from floppy. It generates some sort of error message. If your TDS644A has a second NVRAM it is only for waveform storage and isn't critical to have a copy of its data.