Tektronix 2440 Oscilloscope Repaired- Part 4
Here are the previous article:
https://www.jestineyong.com/tektronix-2440-oscilloscope-repair/ (Part 1)
https://www.jestineyong.com/tektronix-2440-oscilloscope-repaired-part-2/
https://www.jestineyong.com/tektronix-2440-oscilloscope-repaired-part-3/
Today I opened the already completely repaired 2440 Tektronix Oscilloscope again to try and fix some of the remaining FAIL errors. (FAILs which were mentioned in the already published 2440 Repair articles part 1 to 3)
I wanted to start with the 3000 FAIL concerning the U664 SRAM on the A12 Board. So I checked the Boards with U664 , and U424A by touching all components with my fingers for hot spots again. And I was trying to test some of the signals on U664 with Probe Channel 1. But to my surprice at Start-Up/Powering Up the 2440 Tektronix Memory Scope, all of the 3000 Fails had gone.
Something had changed because a 6000 FAIL message “ CKSUM NVRAM* ” had added itself to the FAIL list. And that part has not been there before and could mean an empty Lithium Battery problem.
And because my previous message at address 3000 had gone I took another try in Fixing the remaining errors by the Scope’s Built-In Self Diagnostics. But I first closed the Oscilloscope again, so the FAN could effectively keep all components from over-heating.
After a 10 minute or so warming up time with the Oscilloscope case closed (when the warming up first warning on screen disappears from the screen the warming up period is complete) the SELF CAL routine can be started by first pressing the MENU OFF/EXTENDED FUNCTIONS button. (like explained in the previous 2440 repair articles).
And after some time RUNNING, the PASS message appeared above the SELF CAL choice on the screen.
And next I did the same with running the SELF DIAG choice on the screen. And to my happy surprise also this test had automatically PASSed itself after RUNNING.
So when I now startup the 2440 Scope by pressing the ON/OFF Button, the “running self test” message only briefly shows on the screen, after which every Diagnostic Test comes up being all PASSed.
And the Tektronix Scope has completely fixed and Calibrated itself!
Following photos prove that the 2440 is completely working as it was since 1988.
On previous photos the SELF CAL diagnostic has passed. (I better wait until the scope gets Warmed up before continueing with the SELF DIAG. By pressing the button under that text on the screen.
Photo above clearly proves what a great piece of Hardware Tektronix really is!
I just saved myself $600 dollar on Calibration Costs by letting the Scope run its own Built-In Diagnostic!!
Next photos show that the 2440 Oscilloscope is ready to read the signals on Channel 1 and Channel 2.
I earned my Coffee break and placed my cup on the sturdy Tektronix Machine.
This concludes my Tektronix 2440 Memory Oscilloscope repair. And my good friend Frans now has to buy a pair of 300MHz Probes because that is the only thing he didn’t get with this previous Defect but now magnificent instrument.
So to you all… buy or repair such a great Tektronix Oscilloscope. If I can do it so can you!
This 500MS/s 300MHz Tektronix Scope can still easily compete with todays oscilloscopes after almost 30 years !
Albert van Bemmelen, Weert, The Netherlands.
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Zed Pato
October 9, 2015 at 2:51 pm
good job sir
Albert van Bemmelen
October 9, 2015 at 6:44 pm
Thanks Zed, Glad you liked it.
Humberto
October 9, 2015 at 11:01 pm
Good repair Albert. An oscilloscope is a necessary tool in our workshop.
Albert van Bemmelen
October 10, 2015 at 4:38 pm
Still my Digital meters are my most used devices of all of my test equipment. Although my meters still can't measure true RMS AC Voltages and Currents. And only sinusoidal waves are measured correct. DC measuring is never wrong. Only the LCD digital display can be to slow if any Voltage or Current would change to fast to be displayed. Which in any casy can always be easily made visible on a oscilloscope.
Anthony
October 10, 2015 at 3:44 am
Sensational repair Albert, Well done and congratulations to you ! Thank you for sharing the repair with us.
Kind Regards
Albert van Bemmelen
October 11, 2015 at 5:58 pm
Thanks Anthony! I'm very pleased with the perfect results too!
amendar
October 10, 2015 at 6:49 am
Hi Albert,
Wonderful, I am glad all tests, cal., diag. passed.
Could be any ogical reason?!
Good luck an go on
amendar
October 10, 2015 at 11:58 am
Wonderful,
I am glad all tests, cal., diag. passed.
Could be any logical reason?!
Good luck an go on
Albert van Bemmelen
October 10, 2015 at 4:24 pm
You mean.. why the 3000 SRAM Fail disappeared out itself?
Maybe I interrupted the Ext Diag jumper on the U664 SRAM Board briefly unintendidly while touching the components searching for hot spots. And did it change the Diagnostic Fail List.
I'm not sure Amendar because something like that is hard to measure afterwards without doing all test over again.
But the 6000 Fail could be triggered because of that. Sadly I didn't take pictures of the Scopescreen because the messages were dissolved before I knew it. And I don't want to open up the 2440 scope again especially while it now works like a new Fully Calibrated one. Also my own 2465A Tektronix oscilloscope has a Diagnostic test Built-in that runs automatically at every Startup at powering On. And we only need to Calibrate or repair the parts that fail in the Diagnostic Test.
Robert
October 11, 2015 at 3:35 am
Great article Albert. One thing though, After all that hard work I wouldn't risk putting my coffee on top of the scope!!!!
Cheers
Robert
Albert van Bemmelen
October 11, 2015 at 5:49 pm
That's just what my friend Erik said! Would you believe it?
I answered him that he shouldn't worry because I probably would know how to repair a short current problem. As you know that is what I did when I first fixed the Oscilloscope because it only blew up all Power fuses. And I drink very fast so there probably wasn't any coffee in the cup left.
Robert Calk
October 11, 2015 at 4:42 am
Congratulations, Albert. I'm glad that you got the scope repaired.
amendar
October 11, 2015 at 5:18 am
Thank you Albert,
You explained clearly, the jumper can be reason.
ZGood luck.
Albert van Bemmelen
October 11, 2015 at 5:53 pm
Hope your 465 Oscilloscope is how you hoped it would be. If you already bought it of course!
Paris Azis
October 13, 2015 at 3:10 pm
Hey Albert
I fully understand now, upon completion of reading this last article of yours, the reason that you forgot to shave yourself and your beard appears as noticeably grown…What an amazing “digital thirst” is the one you have man!
Well, keep on coding, decoding, multiplexing and demultiplexing, searching for glitches in your digital signals, but remember! All of it exists only in order to represent in the highest possible accuracy the really magic world we live in. The world of the analog signals which the entire Mother Nature provides and works with…
Thanks again for your effort.
Albert van Bemmelen
October 14, 2015 at 2:50 pm
Thank you dear Paris. I appreciate your kind comments very much. But I probably wouldn't search as far as the Magical World you're painting. It is after all only a bit of Science without the Fiction. Maybe in the not so distant future it also will be possible to shave without having to shave yourself. Because that is a thing I do not want to waste time on since it just keeps on growing whatever I do. About this Tektronix repair I just didn't knew I was able to do an article on these quite expensive and above all Magical designed Tektronix devices until my friend brought this 2440 Oscilloscope to me for repair.
Paris Azis
October 14, 2015 at 8:59 pm
This is what most people call “learning by doing” Albert.
And interpreting it sequentially backwards up, “you did it, you learned it and you have written it”. Plus, you did it good!
Greetings
Thomas Niedermeyer
March 25, 2017 at 2:46 am
Interesting and instructive article, Albert. I recently acquired a fully functional 2430A with very few hours on it and a non-functioning 2440 that was thrown in with the deal. The LV power supply in it is working and putting out the correct voltages, but the scope never fully comes to life. There is no trace, although I'm pretty sure the HV supply works because there are some light flashes on the screen when I turn the unit off. The power-up comes to a halt with all 3 GPIB lights on and the second and third of the five trigger lights lit. I have full documentation for both units. Any ideas or recommendations would be appreciated. Warm regards from Austria. - Thomas
Albert van Bemmelen
December 10, 2018 at 7:33 pm
Hi Thomas. Sorry for my late reply. I do not check upon my older articles to see if someone had posted any new questions. And I do not think that many of us do.
But to answer your question, I think that most likely at least one of your Tektronix complex mainboard chips must be failing. In my 2440 repair it was a A/D converter chip that caused the internal main power supply to blow. And it shorted out the AC 230V input voltage and blew a fuse and the diode bridge rectifier to kingdom come. In my 2440 Tek like in yours there are quite a lot of those complex dedicated chips placed on the mainboard(s) and I was lucky to easily find those complete service manuals for my scopes. And if you need yours for your 2430 scope you'll find it here: https://www.tek.com/manual/2430-service-manual. I think the best thing you can do is to follow the structured flowcoded service diagrams in your manual and start with the easy to check tests. Without it servicing such a complex device is a bad idea. I never opened a 2430A before so I can't point out anything that would be of any help. But in case you have the money and the time, sometimes you may be able to find a complete working second hand used board or an identical scope not working with spare parts on eBay you could use. Good luck with fixing your 2430A scope!
Albert van Bemmelen
December 10, 2018 at 7:47 pm
Oops: I noticed you mentioned 2 scopes of which only the 2440 needed fixing and not the 2430A that was still fully working. In this case my advice still would be to start with checking the flow diagrams in the servicemanual. The manual for our 2440 is downloadable here (much smaller in size than the 2430 manual which is a large 153MB!): https://www.tek.com/manual/2440-service-manual
I hope you also still are able to find any replacement parts like I did with the A/D converters I needed for my 2440 repair. My warm regards from the Netherlands. - Albert (;).
Albert van Bemmelen
October 12, 2021 at 3:09 pm
Update 12-november-2021: Yesterday I now also fully calibrated my Tektronix 2440 scope externally!
And I also first upgraded my oscilloscope by replacing both old battery backupped 32k SRAMs U664 and U350 by FerroMagnetic FM1808 DIP 28pin chips. Because without the calibration data in these chips the scope won't work, no working screen, no nothing, so I also used the uploaded firmware bin files from this great guy - see following link - to keep my 2440 alive after replacing both SRAMs. And pre-programmed my FM1808 with them so my scope would still work to be able to calibrated it again afterwards! Those bin files (from an almost identical 2430 oscilloscope) can be found here: https://www.diyaudio.com/forums/equipment-and-tools/312894-tektronix-2430a-lost-cal-data-repair.html . And if you have a dead 2440 most likely these SRAMs lost there original firmware and need to be restored first! PS: I used my even almost as old SYSTRON 100A Pulse Generator to finish the last external CTE calibration check. And I now have a fully Internally (Selftest) and externally calibrated Tektronix 2440 oscilloscope. Also the above given link provides the easy Calibration steps you can follow. And in Part7 of this Youtube video you can see how to setup the signal for the final CTE calibration step: https://www.youtube.com/watch?v=lvCRK7JbcYs
Albert van Bemmelen
December 17, 2021 at 8:28 pm
And in case your 2440 or 2430 scope doesn't startup, behaves erratic, or simply freezes in the middle of a measurement, it also may be caused by bad capacitors. Which means its time to replace the old capacitors on those board(s). In that case checking following link may be useful: https://www.eevblog.com/forum/repair/tektronix-2432a-repair/
Kurt Moser
April 26, 2023 at 3:52 pm
Hey Albert,
According to Your 4-part series where You show the repairing of a Tek 2440, it seems
that You are a specialist of this scope. My 2440 shows a very strange effect.
It is to mention, that no of the built-in tests fails; everything seems to be ok !
But the scope beahves like it had only a sample rate of 250 MS/s.
The picture which I uploaded here to the Dropbox
https://www.dropbox.com/s/ud9l484lbxabmkp/20230417_132059.jpg?dl=0
was taken with the following settings:
Acquisition: Envelope Trig Mode: Singe seq. Trig. Pos: 1/2
The input signal was a 20 MHz sinusoidal waveform with 1.2 Vpp amplitude.
One can cleary see, that the A/D-converters change its output after 4ns but
at the same time.
My question is: Do you have an idea of what is going on here ?
What would you suggest to do ?