TDS-754C Renders Tektool floppy backup unreadable - Page 1
Forum section: electronics / testgear

author: amaschas
author_rank: Regular Contributor
timestamp: December 01, 2024, 06:33:41 am
content: Hey all, I have a TDS-754C that I've posted a few threads about as it appears to be a singularly problematic device. It has various problems, not communicating over GBIP when in unlocked mode being the primary issue, and I'm trying to dump the NVRAM EEPROM using the tdsNvramFloppyTool-extra tool in the tektool repo so I can avoid bricking the device while working on it, but unsurprisingly I've run into a bizarre issue. The scope seems to write to the floppy fine, and I can see the backup files on the floppy, but the backup process appears to have altered the floppy filesystem such that nothing can be read from it. I've attempted formatting the floppy both on a windows machine and in the scope itself, and the backup seems to create files on the floppy in both cases, but nothing can be read from the floppy once the backup has been created.My only option for reading/writing the floppy is a USB floppy drive, which reads and writes everything fine _before_ the firmware backup, even if I've formatted the floppy with the oscilloscope, but afterwards it only shows the files on the drive, reading and writing throws a variety of errors depending on which operating system I'm trying to use.Just as an example, I'm current using a Ubuntu system to try to read the floppy. I format the floppy in the scope, move it back to Ubuntu, copy dumpall.app and startup.bat on the floppy, then insert the floppy into the scope and power it up. A few seconds after powering up I get a message that the backup succeeded along with a beep. When I check the floppy in Ubuntu again, I see that the original dumpall.app and startup.bat have been renamed to d and s (this doesn't happy every time), I can see all of the files on the floppy, but trying to copy them results in "Error splicing file: Input/Output Error".I'm honestly leaning towards getting rid of this scope since it's been so much trouble at this point, and appears to be causing problems that no other version of this scope does. But I figure if I can at least backup the memory I can start making more drastic changes.

author: 44kgk1lkf6u
author_rank: Regular Contributor
timestamp: December 01, 2024, 03:19:27 pm
content: Since the long file names got corrupted, I would try to make it easier for the oscilloscope by making sure that all the file names are 8.3. That is, naming the files DUMPALL.APP etc. and making sure that no unnecessary files exist such as the system volume information thing if the floppy was accessed by Windows after being formatted.If it is the computer giving the input/output error, dmesg usually contains a more specific error message.My oscilloscope has the opposite problem. It can copy files from the hard drive to a floppy but has problems copying files from a floppy to the hard drive. I have only had to copy files to the hard drive once. I ended up using GPIB.I don't have much experience with floppies. But there should be plenty of information on what to do if a floppy drive doesn't work right.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 01, 2024, 03:30:08 pm
content: After the backup succeeded can you see the files on the floppy using the scope? (I assume that you can list the files there, I don't have one.) If there are only 2 or 3 files on the floppy they occupy the same directory sector and the scope has to write that sector back to update the directory. If you can see the files on the scope my guess would be that the floppy head(s) are misaligned. Also, make sure that the floppy is of the correct type, another guess from me is that it should be a 720KB floppy and not a 1.44MB.

author: nctnico
author_rank: Super Contributor
timestamp: December 01, 2024, 04:11:21 pm
content: Mis-alignment between drives is the most common problem AFAIK. Unfortunately the quality of floppy-disk drives has fallen a lot since the old days which makes exchanging data between two systems using floppy disks a huge challenge. What may help is to format the disk on the target machine and then try to read it using a PC attached disk drive.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 01, 2024, 05:19:11 pm
content: Quote from: PA0PBZ on December 01, 2024, 03:30:08 pmThese scopes do use 1.44Mb HD disks.My money is on misaligned heads too.A good excuse to install a floppy emulator...

author: amaschas
author_rank: Regular Contributor
timestamp: December 01, 2024, 07:54:04 pm
content: Quote from: PA0PBZ on December 01, 2024, 03:30:08 pmInteresting, so if Icansee the files on the scope, its an indication the heads might be misaligned? I can in fact see the files, the file sizes and even the original names when I view the files on the scope:It is interesting that a disk formatted in the scope can be read and wrote to by other devices, but not after files have been written,

author: amaschas
author_rank: Regular Contributor
timestamp: December 01, 2024, 11:07:05 pm
content: Progress! I was looking at the floppy drive in the scope, and figured that given the size of the USB floppy drive I used to read the disks it might be use a similar flex cable to connect. If the issue was with the floppy drive hardware, I could maybe work around it with a different drive. Long story short, it worked great, just a little annoying to keep having to detach and re-attach a floppy drive ribbon cable for each step. There are still oddities of course, the firmware dump passed verification but claims to be v5.2e, rather than the v5.3e advertised by the scope, and the EEPROM dump failed verification, but it feels good to have at least solved one (1) problem with this scope! Thanks for all your help!

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 01, 2024, 11:17:16 pm
content: If the heads are misaligned, the disk drive will read it's own misaligned tracks just fine.Youmaaayyyybe running into bugs or just earlier firmware that doesn't fully support the memory dump software.On my TDS784C, I had to upgrade from v7.2e to v7.4e for things to work properly.However I'm pretty sure you can't upgrade a major revision level (i.e. v5.x to v7.x) without a corresponding hardware change to suit, and I'm not sure if, say v5.3e is functionally equivalent to v6.3e just for a different hardware revision. I'm not 100% sure on where the boundaries lay for that sort of thing.

author: amaschas
author_rank: Regular Contributor
timestamp: December 01, 2024, 11:55:50 pm
content: Quote from: TERRA Operative on December 01, 2024, 11:17:16 pmI did actually try the scope drive with the little floppy USB adapter that I pulled from the USB floppy drive and my Ubuntu system wouldn't read anything from it. Tried both a disk that had been formatted and written by that drive and a fresh floppy and both threw read errors. But using the new drive in the scope appears to work perfectly, I just tried the tool that only pulls the EEPROM from the scope and managed to get a dump that passed verification, albeit also claiming to be a v5.3e dump. I think I'm confident enough in these dumps to try desoldering the two memory chips and socketing them for eventual upgrade. I actually dumped the EEPROM three times to three separate floppies since I feel like the EEPROM calibration is probably the most pain in the ass thing to lose, and they all passed verification with identical checksums.One thing I really want to try is to upgrade the scope to the latest 5.x firmware to see if that helps with any of the other problems like the GPIB thing, though IIRC I would have to recalibrate the scope after doing something like that? Successfully socketed the two memory ICs. First step finally completed!

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 02, 2024, 05:21:50 am
content: The cal data on these scopes is in two EEPROM chips on the acquisition board, so totally seperate to the firmware.I would suggest dumping your current firmware and NVRAM via GPIB using the tektools app available somewhere on these forums as a backup, then upgrading the firmware.That way you can always go back.I've found it's pretty safe. The bootloader is seperate, so even if you get a bad write, you can always reflash.I've even tried deliberately flashing the wrong firmware, and it was recoverable by going back to the original backup.

author: amaschas
author_rank: Regular Contributor
timestamp: December 02, 2024, 05:58:52 am
content: Quote from: TERRA Operative on December 02, 2024, 05:21:50 amSo this is the scope I've made a few threads about that doesn't respond to GPIB when the NVRAM is unlocked, so none of the tektool scripts that rely on GPIB work. Dumping via floppy was my only option unfortunately. Is there something else I would need to back up that I didn't get via this process? I thought the NVRAM backup was the firmware, and the EEPROM backup was the calibration data, but maybe I'm misunderstanding what those dumps are? Ultimately I'm hoping that by upgrading the firmware I can get GPIB working in unlocked, but I wanted to back everything up first.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 02, 2024, 06:07:09 am
content: Aahhh, I forgot about the GPIB problems..There are three things to backup. Firmware, NVRAM (enabled options and user settings mainly), and Calibration Data.Firmware and NVRAM is on the processor board, and Calibration data is on the Acquisition board.I don't think it's possible to move the firmware through the floppy drive as it is too big to fit on a disk IIRC, even Tektronix did firmware updates over GPIB.

author: amaschas
author_rank: Regular Contributor
timestamp: December 02, 2024, 06:10:06 am
content: Quote from: TERRA Operative on December 02, 2024, 06:07:09 amAh OK, so I'm likely OK with NVRAM and calibration data, but I'm guessing without GPIB I don't have a good way of dumping the firmware? Man this weird GPIB problem is a huge pain.You know, now that I think about it, is there any reason the scope would need to be unlocked toreadthe firmware? Maybe I should give the tektool a shot with the scope locked?

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 02, 2024, 09:11:13 am
content: Yeah, Ithinkfrom memory you can read the firmware out when the scope is locked, just not write with the switch in locked position.May as well try anyway, the switch will prevent any damage being caused.