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TDS744A at firmware v1.0e - is it worth to upgrade? Changelog?
Posted by Rafiki on 08 May, 2024 09:43 -
This is my first post to this forum. I've to say a big thank you to all of you who've given me so much infos about my scope and so helped me to repair this old device. Without the help of different posts and links to schematics I wouldn't have found the broken MLCC on the acquisition board which prevented the power supply to come up.
I've also removed the jumper resistor and the caps to upgrade to TDS784 and I also replaced all the relays on the hybrids cause I read these could be the reason for calibration errors. Unfortunately acquisition calibration still does not succeed. I also build the cable for the console port but when attached my scope don't boot. Pulling off the cable on the console port and attach while booting shows me some messages on the terminal program. So basically it works. But no matter what I do with the handshake signals (RTS, CTS, DTR, DSR, RI, ...) the v1.0e firmware seems to stop booting when console port is attached. I read on different threads that may be the case with some firmware cause others faced the same problem.
Now I wonder if it's worth to upgrade the firmware. I found on the net v1.1e and even v4.2.1e. Is it worth to upgrade? Is there some changelist?
To fix the calibration issue I thought I need a working console port which leads me to the question if I should update the firmware -> even more work and time for repairing this unit. In the current state to scope works. Just reaching the 1GHz (about 3dB on all 4 channels). So I could do with it what it is supposed to do (measuring my own electronics). Or should I even invest more time in fixing/enhancing this scope? Upgrading firmware in the hope to get console port fully working? And maybe enable option 2C and 2F? Thinking out loud.... -
Be careful with the firmware versions.
I haven't completely figured it out, but I believe that the major firmware revisions (I.e. v1.x to v2.x) possibly indicate a hardware revision. That is to say, you can't use v4.2.1e firmware on hardware that has v1.0e originally.
You can go to v1.1e safely.
Having said that, if you use the tektools app that was provided on this forum and flash via GPIB, you can't really brick the scope. If the firmware you try doesn't work, you can just flask back to the original firmware, no harm no foul.
My point of view is to upgrade to v1.1e, then play with higher firmware revisions and revert to v1.1e if it doesn't work. All you'll lose is time (It does take a loonnnggg time to flash with the afore mentioned tool like 45 minutes or so, but it does work reliably) so not so risky.
As the firmware is larger than the available space on a floppy disk containing any flash software, you cannot upgrade firmware using the floppy drive as far as I know. You can backup and restore the NVRAM and calibration data though, details are around the forum somewhere.
Enabling options is possible with a few commands sent via GPIB independently of firmware upgrading, and if you activate an option (as long as you have any associated hardware that may be required) then that change is permanent, even across firmware upgrades.
If you enable an option for which you lack the needed hardware, the scope will still boot and work fine, the option just won't be available (or appear on the boot screen), in that case it's best to disable that option to prevent any potential nuisance errors filling your logs.
I can provide instructions on how to unlock options if you don't know how.
I have heard of the no-boot-with-console-adapter thing before, but I have yet to make a serial adapter myself (I have parts, just need to design PCB's) so I can't comment further on that.
You may find the calibration problem may be due to your unlock to TDS784, as your scope is only originally calibrated to 500MHz. This means the scope is completely uncalibrated from 500MHz up to 1GHZ. I haven't played much with unlocking scopes like this (I have a TDS784C, TDS784D and TDS7894D in my collection of these series of scopes anyway, so no need) so I'm not sure what the reaction of a scope would be when performing SPC etc.
I guess you could always just revert the resistors back to a TDS754 and see if the cal errors go away.
Unfortunately, the setup requirements to calibrate these scopes is rather daunting, so.... good luck with that..... (It's taken me years to accumulate the needed gear.. I can currently go to 500MHz, and with some testing of my setup when I get bench space and time, I can now most likely get to the full 1GHz, once I get the ISA slots in my retro PC running MS-DOS configured...)
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Thanks for the infos. I'm still unsure if I go through the hassles - buying a GPIB card, setting up an old PC with ISA slot (not a big thing for me), playing with GPIB which I ever avoided over the last 40 years ;-) ....
I hoped I can update software easily through the diskette drive or serial port or console port somehow but ...
Building up the console port / serial interface was not a big problem for me cause I've option 13 anyway. Well except understanding the pinning description here. I've made up a schematic cause I needed it to visualize while soldering the cable. I'll attach it cause I didn't find any. As processor board connector I use a cable from an old PC. Guess it was used in some vintage Philips PC from the 286 or 386 era.
Regarding calibration - no the problem existed before upgrading to TDS784A. I've searched a long time for information supplied on the error log but can't find a matching explanation. So I decided to build up the console port cause the messages are cut on the scope screen. But as this does not really work (hang on boot while attached) I decided to remove the jumper and caps as long as I've the scope dismantled on the bench. And thought maybe by upgrading the firmware will repair the 'hang on boot problem with console port'.
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You don't need an old PC to use GPIB on these scopes. I use an Agilent/Keysight 82357B with the current Keysight IO Lib Suite and it all works fine for normal GPIB use, reading out errors, updating firmware and enabling options.
You only need the old ISA hardware to do the actual calibration.
Also, seeing as this is an 'A' model, have you replaced ALL the SMD electrolytic capacitors on the processor and acquisition board? They do need doing and if you are lucky they haven't started leaking yet..... It's a known problem with these scopes. -
There are no (nearly) SMD AL electrolytic caps there. AFAIK these was a problem with TDS5xx not TDS744A anymore.
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From the various oscilloscopes from these series I've had through my hands, I'm under the impression that only models from the early 90's where affected. Also keep in mind that earlier pieces of equipment from Tektronix like the TDS400 series oscilloscope and AWG2000 series waveform generators also seem to suffer from the leaking electrolytics. I've owned a TDS744A myself and this unit had mostly ceramic decoupling capacitors. The few electrolytics it has, didn't leak.