Tektronix TDS420 Oscilloscope 4ch 100MHz 1992 repair teardown

Digital Oscilloscope design is from 1991, i think my unit is from 1992
8.5kg dont feel very heavy, it got IEEE and VGA connectors,
label say 230Watts but mine only ude 140Watts
If you own a similar scope, and like it to continue working,
please asap replace the tiny alu caps !! they will most likely also leak or start to soon in your unit also, many via connections was corroded broken connection to inner layers in mine so it is not possible to repair (or very hard to) all pcb are 6 layers, CPU is MC68020 it also have DSP and parallel memory handling for all 4 channels ADC, quite amazing design.
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#oscilloscope
#tektronix
#repair
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I use auto generated subs, i am sorry there are a few spelling errors,
maybe one day they can do it better..
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(Thanks to all my Sponsors / Traders / Swappers / Sellers / Buyers, without your support and constant flow of cool items in/out, none of this would be possible)

[@owenschwartz]

Love all of the effort that goes into these videos!

[@BogTheWombat]

The presence ofthe GPIB port suggests to me that this was intended for an ATE system. For general lab use you wouldn't pay the price premium for the interface option. The lack of soot inside suggests that either the CRT was disabled, or that the unit was used as a cold backup machine to get the test system back up in the event of a scope failure. It was probably cheaper to have standby spares rather than risk loss of production while failed equipment was repaired.

[@zoubirdjelouah3273]

Good

[@Edisson.]

Hi Thomas, it's a shame to see so much damage on such a well-preserved machine, I myself have such an experience with an RMS voltmeter HP3400 that looks like new, but is completely fried inside. The use of a measuring device for detecting data cables has worked for me several times to find paths on multi-layer boards. I used the trace generator - a function designed to search for cables in bundles and with the help of a search probe I looked for where the path leads, then I checked the target area with an ohm meter. This search was unsuccessful many times, but several times the route was found this way. 😲Look, it works 🤔 ...... capacitors are not needed 🤣 Just a small note: during the self-test of the oscilloscope, the indicators of the individual channels also lit up, at the moment when he tried to inject a signal into channel one, his indicator was off - was the input switched on? Nice day 🙂 Tom

[@TeardownOZ2CPU]

this is a really nice scope, so i am sad to give up for now, the scope is now in the hands of a more patient type of person, i am sure he will find the broken tracks on the button input board so it react on user inputs, then the rest will be easy

[@Edisson.]

@@TeardownOZ2CPU Great, let me know how it goes

[@riccardoruotolo6862]

Frontal lobotomy complete. Zombie oscilloscope lives!

[@michaelturner4457]

Early 90s does seem to be the worse period for surface mount capacitor plague, whether it be test equipment, video and audio equipment, etc.

[@Slickrock72]

Incompetent Chinese technology theft plus massive Chinese counterfeit capacitor infiltration into component supply chains is to blame.

[@OneBiOzZ]

the CRT looks very nice if you cant save the scope at least save the CRT and drive electronics could make a fun little project

[@mrnmrn1]

Probably not all those corroded vias are open. Just be sure to remove and neutralize all the capacitor juice. I don't know if detailed schematics are available, but if yes, it should be repairable with bodge wires.

[@LutzSchafer]

What a shame. Such nice scope almost totaled by leaky caps.

[@RensePosthumus]

So sad. Desolder the IC's and look for a new video object would be my suggestion.

[@idleprepress]

Who needs capacitors in 2024 ^.^

[@TeardownOZ2CPU]

look mom, no capacitors :-) i am sure all the electrolytics are for hum area suppression , to get it up and running to a looks like all is alive, we dont need to mount them. better spend the time of finding the missing via connection and get the user interface alive

[@idleprepress]

@@TeardownOZ2CPU sure they're all power filtering ones, but anyway that's always funny when you just leave a good handful of components apart and it fucking works. Good luck with the rest of work. Hope there's no deep inter layer damage occurred.

[@inse001]

Actually the specs say 100MS on all channels, but nevertheless I personally don’t see any reason for investing effort into this unit. No special features, no storage medium, low sample rate, mediocre bandwidth, low memory (15k points). A top range analog scope (2465 eg) or digital beast like TDS 654 is worth restoring but this one- nah (imho)

[@TeardownOZ2CPU]

hobby is hobby, dont always need to make sense if we calculate hrs worth of usage or profit or such :-) sometimes it is just for the kick, can i find the error, can i fix it , 48 hrs later, i give at away for 10 $ or trade it for another broken item :-)

[@inse001]

@@TeardownOZ2CPU Of course hobby is hobby, but it’s much more satisfying to restore something and enjoy using it afterwards, not having to give it away it as nobody wants it (including yourself).

[@TeardownOZ2CPU]

@@inse001 sometimes i am lucky and score very cool and very usefull items too, so it is not always for the kicks, i actually get a bit sad when i have to give up repairing very cool items, but sometimes it is just impossible at the time and money i am ready to put into it.