Tektronix TDS 744A teardown and repair 2

I continue working on the 1990s Tektronix TDS744A digital 4-channel 500 MHz oscilloscope. My plan was to fix the colors, but I ended up taking a closer look at the switching power supply board, testing and replacing a lot of high ESR electrolytic capacitors, fixing a board damage from electrolyte leakage and relubricating the fan. I did some experiments with the sequential color system. The color shutter has no voltage going into it. There's definitely a problem in its driver, but the shutter itself might be deteriorated too. For now, I decided to remove the color shutter. This gives me a bright monochrome picture. The oscilloscope is perfectly usable this way. I might try to put the shutter back in and fix its driver, but I'm not sure I want to spend my time on it, risking an accidental damage, as this oscilloscope is perfectly usable as it is now. This old Tektronix oscilloscope uses a CRT-LCD hybrid display technology - a monochrome CRT tube with a solid state sequential color filter (liquid crystal color shutter / LCCS / LCS / NuColor).
The 1st episode:
• Tektronix TDS 744A tea...
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[@AllLoudNation365]

"Changing these crapacitors..." lol

[@drobotk]

That caught me off guard lol

[@amydamon2323]

I always learn a lot from your videos. Thank you for making them "bloody long". Two nice things about your videos are that you don't repeat yourself half a dozen times and don't teach us the same basic things in every video. That saves your videos from being "excessively, redundantly bloody long". Kudos for that. Keep up the good work!

[@2001pulsar]

Maybe a cheap LCD display running from the VGA output would look OK.

[@LawpickingLocksmith]

Still a good score. 500MHz is not cheap even technology changed a bit. I am still fixing my 100MHz Hitachi analog.

[@DiodeGoneWild]

I plan to fix a 2 channel analog 120MHz dual time base BM566A ;)

[@eskisful]

I want to see you replacing those timers with rotting batteries inside.

[@barbudoru]

I highly recommend Necroware's method to refurbish those RTC nvram modules, he recently published a video called "Let's talk about RTC options once again" discussing the topic.

[@DiodeGoneWild]

Thanks ;) interesting video. I think the RTC (DS1486) already has the battery discharged, as it says the year is 2040. I don't think a clock is that important for the oscilloscope. But the BQ4015 is the NVRAM, it might be more important. But does it really contain the callibration data? Isn't it just for the user settings, to remember things like time base, voltage/div, maybe the color settings for the display. But I guess this one still works as the brightness settings are still remembered without mains. But the most important thing is - were they really that crazy to put the callibration into NVRAM? Isn't this in some EEPROM (flash) instead?

[@barbudoru]

@@DiodeGoneWild The DS1486 also has a small amount of NVRAM in it, which was used in old computer mainboards to hold the BIOS configuration. I wouldn't exclude the possibility of having the calibration constants in NVRAM, the battery life on this kind of module is >10 years, some still work after 20, so they probably considered it "good enough".

[@SimonBauer7]

0:57 maybe make a pass through cable, so that one side plugs into the scope shutter and the other into your cable which plugs into the scopes control board?

[@1pcfred]

It is amazing that scope was working with that big skid mark burn in the board it had.

[@Fluxkompressor]

Watching you solder with that sledgehammer of a soldering gun expecting total incineration I must say: Best solder job I have seen with the tools given Imagine what you could accomplish with a proper soldering station!

[@a.lisnenko]

The oscilloscope is interesting. Please continue!

[@trebushett2079]

And then, for something completely different, he brings in a thorium mantle and geiger counter!

[@hempbear]

If a CRT is fed way too high anode voltage it starts producing X-rays. I guess that he was checking

[@madscientist15808]

Nice vid. Maybe you could try to solder some thin wires to the connector of the color filter and route them to the outside of the case. This way, you can reassemble the oscilloscope and still have access to the signals. Also @ 3:42, fully agree with you, I feel the same way.

[@jeroenjeroen]

I like the more extensive videos; if people don't want to watch it, let them be. I'm sure more people like to watch videos in depth!

[@user-mz1uh4ju1n]

Corona OK, WTF IS THAT 🤣 I think that it means the corona discharge of the CRT but still funny 😂

[@beatrute2677]

damn man, tough fix this one.

[@michaelturner4457]

Tektronix would have had jigs and cable extenders for testing and repair.

[@jbuchana]

Exactly my thinking. I know they had them for much earlier models, as I had them and used them when repairing 545A and similar 'scopes for resale back in the '80s. If my father were still alive I'd show him this video, he was a service technician at Tektronix from the '60s through the '90s. He'd probably have some insights. Great video!

[@GadgetUK164]

Brrilliant! It would be cool to revisit the colour shutter stuff! And those Dallas chips really need dealing with - you can either retro fit a battery holder to each, or remove the plastic casing which holds the battery onto the top of them (there are a few videos on how to do either mod) - but backing up their contents might be required, unless they just hold calibration data?!?

[@German_byte]

Thanks. Btw I love your Soviet era soldering gun. Nice.

[@daniloxyz]

Don't run the thing for too long without a case on, or the airflow from the fan won't reach the ceramic hybrids, they will overheat, expand, contract, and the solder joints of the relays will crack. Ask me how I know... Btw, try to run the Signal Path Calibration. If it succeeds, it will compensate and calibrate all channels (e.g., weird offsets, tiny differences in amplitude, etc.) and confirm the scope signal path is 100% working. If SPC fails, there may be some lingering problem in the hybrids (or somewhere else on the bottom board) and a reflow of the solder joints goes a long way. Also, there are scripts that you can put on a floppy to hack it with all options, but it seems you already have most of them. Nice donation though, particularly because the most expensive part is the 4 probes...

[@Sloxx701]

This era of Tek scopes from the 90s are notorious for having bad caps everywhere, I've rebuilt a TDS 420A and a TDS 540 and it was the same issue and some were leaking. I ended up just replacing all capacitors throughout the scope, probably around a hundred of them. Not a difficult repair, but time consuming and expensive. These scopes are not bad for what you get, if you can get used to the clunky, lagging menu/interface design.

[@wolfrobben6914]

Bloody interesting!

[@CJWarlock]

@9:32 - "crapacitors" (a new word for crappy capacitors) - Ha! Ingenious! :D Congrats on the funny wordplay. :)

[@VIPINSAINI_20]

it was nice, i would like to see this again like part 3 of the video

[@mikeb1013]

Great work, well done. Although it is a shame to now be just black and white, that shutter took so much light I'd just bin it and move on. If it was me I'd get some clear acrylic sheet and cut a piece to stick inside the front bezel and just leave it at that.

[@pietskiet3595]

KZbinr Necroware did a great video on reworking those old RTC modules - kzbin.info/www/bejne/m5S3i6eQnapsmKs He removes the chip and soldered in cell and crystal and replaces them with a battery socket. Also a good idea to solder a socket into the board while you're at it.

[@thecriss88]

There are two type of videos you need to do. One is an SMD soldering tutorial with a gun soldering iron. The other is some political discussion about the current issues in Europe.

[@_________________404]

Based

[@edic2619]

Great video. Thanks.

[@tajtrlik1111]

Ďakujem za ďalší diel z tejto zaujímavej série, kľudne v nej môžeš pokračovať a rád sa pozriem aj na ďalšie diely, ak ich natočíš. Ale pekne si ten osciloskop dal dohromady, teraz ti môže pekne slúžiť a štvorkanálový digitálny osciloskop, to je aj dnes dosť drahá záležitosť a takto si aspoň získal pekný kúsok do dielne.

[@stalkerfromvoronezh4493]

ЖК кристаллы возможно уже просто потекли со временем. Так что эта штука в любом случае под замену. Были у меня часы старые с ЖК экраном - так вот, он так потёк, что полностью перестал работать. Клей в старых ЖК экранах со временем разложился и всё. Кина не будет.

[@Alchemetica]

As it is I would take it as a win giving you a useable 4 channel oscilloscope. If you do at some future date tackle the colour it would be interesting, but as you said it is working and further investigation may create problems.

[@michaelwittmann3176]

Nice video sir please continue making long videos :)

[@farzinfirozian2722]

glasslinger has a vidio about back uping this kind ossiloscope cheaps.

[@adrian_sp6def]

You could check if there is possible to find a composite video signal along with chroma and luma, maybe with that You can generate video signal for external monitor. at that moment there is unclear if color generator circuit is working

[@hugoegon8148]

Similar pain is to work on car radios or multi media systems because of the compact design. 😕

[@Alchemetica]

Thanks! Cat treats : )

[@inseries5494]

you come for the cat

[@sigataros]

@@inseries5494 the cat proofreads the schematic

[@DiodeGoneWild]

Thank you for your support!

[@Roman00744]

For measuring points you don't have access to you can solder thin wires to those points and then measure them when it's assembled and working.

[@SuperHaptics]

I am the guy who is screaming about your soviet era nuclear plant soldering iron😂 . I like your videos mr wild diode, also your crazy soldering iron. Say hi to your lovely cat....

[@TheDefpom]

lol @ 8:45 you know me too well.

[@AKG58Z]

21:21 loyal viewer.

[@radionicretrofit]

We need more scope content

[@DiodeGoneWild]

Well, I have 3 more scopes to fix ;). Tesla BM566A, some tiny soviet scope and Křižík scope. And probably another Fnirsi to review.

[@radionicretrofit]

@@DiodeGoneWild looking forward to it

[@Alexelectricalengineering]

That's so awesome 😎😎👍👍👍

[@graxav]

All the way to the end .. I'm as daft as you are .. 😜

[@kapegede]

40 minutes well spend. This length is no problem at all.

[@thevoidedwarranty]

That LCD module itself is clearly bad ,it shouln'd be spotty like that

[@lmwlmw4468]

Nice.

[@yan7382]

But these oscilloscope have an VGA output connector I believe, you can reuse it to replace the CRT or just use with an external monitor.

[@foobarables]

You should als check the 5V rail capacitors for leakage. They might be leaking as well.

[@inseries5494]

So the one-fix-all decap didn't work! Syuper Niice!

[@git-push]

I prefer it without the filter on. Btw, it's almost always elec capacitors fault..

[@t1d100]

👍👍👍👍👍

[@app0the]

I wonder if the color board is removable then the firmware might know something about detecting it? thus unplugging it might make the display more sensible for a monochrome scenario

[@BDYT1422]

4:44 “Are you kidding me???” Never gets old! XD

[@snik2pl]

There were comments to do lcd mod. This crt is for 90% vga monitor

[@Harry001by7]

Even showing the reasonable capacitances but high ESR might be intended?, or replacing with low ESR ones causes any inrush ?

[@AnnaVannieuwenhuyse]

Your DPOX180H forgets its settings? Mine defaults to 10X, as I saved the settings to the defaults as such. You can save settings as default in the system settings tab.

[@rc_racing1743]

14:35 oh hey, welcome to the future

please do another episode

[@video99couk]

If you have a short persistence of vision, as I do, these colour shutter displays are hideous. Horrible flickering display, great way to trigger a migraine. I can't believe they ever released this product.

[@DiodeGoneWild]

All people have about the same persistence of vision, but some are more easily annoyed by the effect sequential color displays create when they move their eyeballs rapidly. It might be annoying, but it gave it a better resolution than a tiny color CRT would have.

[@video99couk]

@@DiodeGoneWild I don't believe that's true. Back in the days of CRT monitors, I could see glaring 60Hz flicker on a display that some co-workers literally could not see at all. Similarly when we had one of these 'scopes, it made me feel ill but some other people didn't even see what I was talking about. Including, of course, the salesman who sold us the thing. We did get an HP 'scope with a colour CRT but that thing was absolutely huge, heavy and strictly lived on a cart.

[@clusterstorm9522]

"Post apocalyptic capacitor"😂😂😂

[@juperrr]

19:31 Is that a ionizing radiation detector?

[@LMB222]

Yes.

[@DiodeGoneWild]

Yes, it's this: danyk.cz/gm_ind_en.html

[@juperrr]

@@DiodeGoneWild It is diy, wow, love that !

[@labiadh_chokri]

nice video u didn't test the vga output to see the quality and the resolution of the picture .

[@janikpaul1808]

part 3 pls😝

[@adrianking19911991]

These Dallas chips was commonly used as integrated RTC chips for (mailny cheap variants....) AT PC's clones, from 286 era, up to end of 486 era - later Pentium mainboards had in general RTC constructed in other way, and utilized in 90% of PC's much more modern chip, and CR2032 coincell baterry as a backup.... And yes - these Dallas abominations, had INTEGRATED coincell battery inside (technically this is not even a IC, this is PCB with battery, chip, some passives, melted in black resin/plastic...). Nowadays practically every of that Dallases are flat... Some devices, refuses to boot when this RTC battery inside is flat, and spares for this Dallas is nowadays very weak available - and nobody knows how long will work, because these coincells have some lifespan, even not in use. Fortunatelly, there is some modern projects, to replace this with chip + battery holder. There is possible too, to drill a hole in this (yes!), and solder wires for "external power", but.. this is a litte bit "ghetto mod" ;) Greetings from Poland.

[@sanitaires]

Fnirsi требует сохранения настроек. FDD 3.5" проверили?. Лучше снимки экрана использовать. Тёмное стекло вместо фильтра. Может проще LCD монитор встроить?.

[@imanshojaee5109]

Can you try to retrofit an lcd display?

[@DiodeGoneWild]

Why would I ruin such a cool machine by putting an LCD into it?

[@imanshojaee5109]

@@DiodeGoneWild to have colors again?

[@meherhjb7170]

8:46😂😂😂

[@reco9607]

You know Patreon takes much more than other companies, maybe try and check for other companies? I think some people can give you more info.

[@NikhilPore]

Why cant he use soldering iron

[@jcthe2nd]

This is @ThePostApocalypticInventor Approved 😉

[@jcthe2nd]

you and @ThePostApocalypticInventor should do a project together video

[@DeathbyKillerBong]

re soldering "iron", as a wise one once said 'all ways are good, except the bad ones"