Dumpster Tektronix 475 Oscilloscope Repair - Part 1

This is an UNFINISHED video.
My lab is unusable at present and I'm not sure when I'll get around to finishing this, so thought I'd upload what I've got now.
Repair and teardown of a dumpster Tektronix 475
#Tektronix #Oscilloscope #Repair
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[@jasonmurawski5877]

I felt sad inside when this just abruptly ended like that

[@lasersbee]

Likewise....................:-(

[@Commander_ZiN]

I need to see the fix on this one.

[@jafinch78]

I was like... darn stripper... what do you need a another $1. The dance was bad, I admit it. Then starts looking like... huh... what the front door... yep... strip tease. Felt better than the... man... I wouldn't trust the admins tests results down under for the water unless you hired from Flint Michigan water company folks. I was actually thinking he was going to distill the water until I saw the magnetic line and act. Good times... unless the water is that bad. Better get on it fast!!! That's OK... the Tektronix and Military Manuals porn strip tease is typical of the damn... he's not going to fix it now. At least there's great information you can't find anywhere else due to legitimate water quality issues... like... what the pharma and sent us down the drain with China. Check out the latest or a "Kathy Loves Physics" YT'er if you feel sad. Her latest has some leads... wait... is it spelled leeds... got me spooked... or well have that already? It's not D-IX in the water at least and whatever else banned.

[@jafinch78]

Thanks for the lead on the manual too: radionerds.com/images/b/ba/TM_11-6625-2735-24P.pdf

[@jafinch78]

And another thank you sir: radionerds.com/images/8/80/TM_11-6625-2735-14-1.PDF

[@stazeII]

My grandfather was a technician writer for a lot of these old Tek scopes and other gear. Always makes me smile when I hear how much people appreciate those manuals. And think how apparently he wasn’t well liked by some of the engineers. Lol.

[@TractorMonkeywithJL]

That really brings back the memories. I used a 475 every day at work for over 10 years, from about 1979 to 89.

[@RedwoodRhiadra]

"Materiel" - not a typo! It's military speak for "equipment". Because modern militaries love their jargon.

[@hjjfffaa]

Materiel comes from French and has been used to mean military equipment for over a century, now.

[@PaulSteMarie]

Yes, "materiel" is a very old term. The USAF has gone back and forth on that: Materiel Command was split into Systems Command and Logistics Command in the 70s, and then rejoined them in the 90s.

[@DavidKHill]

Yup, Materiel is the correct spelling and is still used today in the USAF. (Air Materiel Command). :)

[@markziza]

" Hey...Mr Hart (Jones)... When you gonna finish eh?! " I want part 2, pretty please. :)

[@whatthefunction9140]

When you repair something I feel very productive for the day.

[@moshly64]

The coax delay line is not for delay sweep, it's so you can see the trigger point.

[@pt8154]

Would love to see part 2 of this repair. I have one of these scopes with a timebase A sweep problem I'm working on. Keep safe!

[@RetroComputerStu]

Im so excited that you are creating a detailed troubleshooting tour of this scope! I actually own one of these. I bought it broken at the local flea market for just a few bucks, but I haven't opened it up to fix it yet. With this video series, I'm hoping that I'll be able to get it working! Im sorry you have to deal with your office getting flooded, I'm sure it's really setting you back. I hope your office gets cleaned up and mold free soon!

[@alandouglas8939]

Ahhh Tektronics 475. I spent a few years connected to one of these. Good times!

[@georgegherghinescu]

Hoping for a follow up Dave! Looks like a interesting repair with the detailed manual and all.

[@boblewis5558]

Used to have one of those back in 1976 - 1978 in the back of my trusty MK2 Hillman Avenger (!!) @ Ferranti as a computer Field Service Engineer. Then I had a BRAND NEW one when I stopped commuting two ways across the Pennines from Bradford to Wythenshawe daily and moved to DEC in Leeds the same year as that scope also as a FS Engineer. GREAT scopes. All the Textronic kit I ever used was fantastic gear. So reliable! They must have really abused that to bugger it and break the knob bezel. Mine were bounced around in the back of various vehicles for years and were practically mint when I left FS and moved to Sales.

[@GadgetUK164]

Looking forward to the next part! =D

[@herbertsusmann986]

Nothing like vintage Tek. Absolute top of the line vack in the day. I had a 475A on my bench back in the early 80s.

[@robhoeye7414]

My first (real) job was calibrating these in 1977. Really need to gradually turn them on, caps dry out over time, dust will create arc paths, some arcs are forever damaging. Need to open it up, smell it, clean it, check the primary supply impedance, remove the un-replaceable vertical output Hybrid, can't remember ever turning a unit on without a CRT (many other memories about those CRT's), did turn on ever newly born instrument with a Variac, slowly bringing up the AC, watching the current. Every instrument would be "burned in" for 24 hours, a many reversed tantalum cap would explode under the thermal stress. One poignant memory is being shocked on my left arm by the -2KV cathode supply, as I leaned on the back chassis, with the safety cover off, I felt that "snap". Whats the hand signed name on the Tested By label on the inner front bezel above the CRT? Ironically I don't own one.

[@richardgoebel226]

That scope was the best in our avionics shop in the 70's. There were constant tug of wars over who got to use it instead of the old tube filled beasts.

[@JamesPotts]

Heh, we still fight over scopes at my Avionics company. But mainly fighting with the people from "test equipment" who want to reclaim your scope.

[@georgegherghinescu]

Old test gear repairs are the best!Make it work Dave!

[@joeybushagour2612]

This is my primary oscilloscope! Rescued it from the dump and just replaced a few tantalum capacitors. Works like a charm!

[@GigsVT]

I have a similar one and I never figured out what that awesome metal delay knob with the crazy multiturn scale actually does. Seems to do nothing. Is mine broken or does it only work in certain modes I've never used?

[@k3ith1]

Awsome. I didn't even watch it yet. This scope means a lot to me. I got one as a gift when I was 14 and I didn't even know what it was.

[@ScramblerUSA]

I think it still deserves to be on the main channel despite being unfinished.

[@Sloxx701]

I love these scopes. I just restored/repaired a Tek 475A (same scope, but 250 Mhz bandwidth and some minor differences). These scopes can have multiple issues as mine did, but they are just so cool looking. Just as a note, all transistors are socketed, you can pull them right out. Same with most of the ICs. My scope was also missing the 5V rail and the -15V rail was all over the place, bouncing between --21V and -25V. The missing 5V rail was caused by a bad main filter cap, the -15V rail was caused by a faulty regulating transistor Q1478. The opamps U1454 and U1464 are also failure points, I just replaced them with NE5532's since finding originals is a pain. All 6 of the main filter caps definitely need replacing as those are the originals in there; two of mine were reading as resistors - they had failed pretty badly. Mine also had a no sweep issue, the trace was just a stationary dot on the CRT. Caused by a faulty JFET in the sweep generator - Q1010. A common fault as well. The tant caps do fail in these, in fact one blew out right in my face while I was probing the power supply. Very similar to the pop you heard when you turned your scope on. I've replaced a few of them, but certainly not all, as there are over 100 throughout the scope. Check the tants on the power supply at the very least. Also the vertical volts/div controls and the timebase controls operate a rotating drum which pushes on mechanical switch contacts, they almost always have to be cleaned, as well as the pots for the trigger level controls. There was a lot more that I had to do but honestly that would be several paragraphs and really what can you expect for a scope that's almost 50 years old. There is an endless amount of info out there for the 465/475's. Amazing machines really

[@EEVblog2]

Thanks. Yeah quite concerned with all the tants and other caps. Makes be hesitant to spend the time on it, because Murphy will ensure there will be a boat load of problems

[@Sloxx701]

@@EEVblog2 - Yeah there usually is with these scopes, they're a work in progress. I didn't believe you when you had said a long time ago that a good scope can be had for around $50 on Ebay, but that's eventually what I found. A completely dead 475A and a dead Tek TDS 420A. $60 shipped each. And if it's completely dead it's almost always the power supply, which is repairable. A good multimeter and some basic knowledge, research, and a little time and it's not too difficult. I just got done with mine a few weeks ago, if I can do it anyone can - imgur.com/a/SH6hLrt Edit - Actually I probably need to sell these things, running out of room. Hoarding old, broken test equipment I bought from Ebay and repairing it seems to be my issue now...

[@grahambambrook313]

About time to continue with this repair, Dave! 😁

[@bratwizard]

I have one of those. Mine is rated for 300MHz. It also has the DM module on top, though that has a bit of a problem these days. I've had the thing for several decades now and I still love it! Works great and it comes in handy quite a bit. Of course, it's a bit of a beast and these days I tend to use my Tektronix TDS220 LCD scope. It works pretty well and is a lot lighter and easier to carry around.

[@funkyironman69]

Great video, waiting for Part II. :)

[@StreuB1]

Looking forward to more on this. That scope is a great scope. Hope we can see a bit of a fixer-upper on it, if its possible. Thanks Dave and hope the lab gets back up and running soon.

[@jeffreystroman2811]

Love the old two channel analog scopes, this is one of the ones I used to rely on. I actually drive around with a 15meg two channel in my car, I really need to clean my car out.

[@witeshade]

While you wait for your lab you can ship this off to Mr. Carlson's Lab and we can all watch a 2 hour video with 4 minutes of content and 35 minutes of ads for his schematics you can buy on patreon.

[@l3p3]

4 minutes of content only? Show me that one!

[@herbertsusmann986]

Ditto that! That guy is over the top. I un subbed him a long time ago. Couldnt take it anymore.

[@witeshade]

@@herbertsusmann986 I still watch his videos sometimes but I have to watch them at 2x speed, and if it becomes clear that the whole video is specifically designed around using his probes and testers then I just stop watching. He does a lot of good work and deserves to make money as much as anyone else, but he really needs to work on his presentation. Dave here at EEVBlog sells plenty of stuff too but he doesn't come across like a shill for himself.

[@Commander_ZiN]

It's awesome watching you fix things I could never fix. Have you ever thought about doing a tutorial series on how to do basic troubleshooting and ramp it up towards advanced? I know I'd watch them all if it was paced right.

[@imegaknow]

I feel the need to buy 1979 scope. Thank you for being optimistic

[@BrightBlueJim]

I've gotten quite a few 1970s scopes running in the last decade. They're relatively easy to work on because for the most part, they use standard parts that can still be bought. This got much worse in the 1980s, when everybody (Tek included) started using specialized ICs everywhere. Just make sure you can find a service manual online before buying anything.

[@rollinhand4750]

Wath happen with the tek tds with a new screen repair no continuation on the proyect? try to finish that mone please

[@cjs1982]

Very useful information! I have a Tek T932 that won't even power on at all, and the knobs for Channel 2 are missing. Hopefully some day I can fix it, or get it fixed.

[@thiagoennes]

"EB" says the grafitti... if this turns out to be an extended april's fool video with "this old tony" levels of time travelling, I won't be mad.

[@robbieaussievic]

....... Dry large cap pad with arc carbon at 6:20 under right leg of 5w resistor.

[@qwaqwa1960]

Best front panel ever.

[@williamsquires3070]

8 volts - yeah, I can just hear the 74-series TTL chips screaming 🤬

[@zrobotics]

Ironically, I spent last weekend w/ this exact same model on the bench, also w/ HV power supply problems (although thankfully, no arcing, just not enough voltage to drive the CRT). I just love the way these old scopes look on the bench (and no boot-up time), but I am dreading the nightmare that will be cap replacement. This definitely isn't the easiest device to service, since just getting the boards out of the chassis is quite the endeavor.

[@SzymekCRX]

Got one :) working and very good condition :)

[@cheewurz]

Dave...I have a 465B Tektronix Scope that I am working on. It looks nearly Identical to your Scope there. Problem - both Traces are too Short! It seems to be in the Horizontal Section but I can't find it nor can I seem to find any help with it online.

[@fredyearian4968]

The delay line is NOT the delayed sweep, it allows one to see the trigger. The sweep has to have time to start when triggered, but the signal that caused the trigger would be long gone... By delaying the signal we can see the signal at the trigger time.

[@soothcoder]

You missed what I thought was a fun thing about these - note all the transistors are socketed. The chips and ASICs too (like the vertical pre-amps with the big fins) but actual individual transistors are socketed. They must have been expensive!

[@HansDelbruck53]

This video takes me back to the early Seventies and beyond when I used to repair and calibrate these wonderful Tek 'scopes as a technician in the US Army, so it's quite nostalgic for me. Oh yes, Materiel (spelled and pronounced that way on purpose) is a common expression in the US military for all sorts of military equipment. I suppose they spell it that way to differentiate it from material fabric. We used to call the tantalum capacitors jellybeans. By the way, I enjoy your videos immensely, in spite of your voice sounding like your nuts are caught in a vise. I've become used to it now. Cheers from across the big pond.

[@Screamingtut]

I used to use one of them back in the late '70s when I worked at DEC.

[@Damien.D]

Great Scott, we all know who EB, who have signed this cap, is. Anyway, that is one hell of a cliffhanger here. Where does the popping sound comes from? Will the scope be fixed or suffer more damage? You'll see in the next episode or in another space time continuum where the lab had not been flooded. Damn these quantiq weather butterflies.

[@matjazlesnjak4983]

i have tektronix 5115 aka(5103) with same popping sounds. what do you think it is the problem??? my 5115 still works tho...

[@Direkin]

The era of hand drawn traces and service manuals.

[@BrightBlueJim]

But that manual is the military version. The original Tektronix manuals had two-color schematics! Black and light blue, although I can't remember exactly what blue was used for.

[@JohnMeshelanyJr]

What test leads are those? I totally need a set

[@darrelleaton8404]

When you're through with that techtronic telescope what do you plan on doing with it? The reason I ask is I really could use a decent working scope.

[@scharkalvin]

I've got a 465 scope which is the earlier version of that. Mine was purchased off ebay as a reconditioned unit in good condition. Nice scopes.

[@BrightBlueJim]

Not earlier - the 465 and 475 were both introduced at the same time and produced over the same period - from the late 1960s to mid-80s. The 465 was the 100 MHz workhorse, while the 475 was for people who needed higher performance (200 MHz for the 475, and 250 for the later 475A). If you didn't really need more than 100 MHz, the 465 was actually a better instrument, because it wasn't quite as close to the bleeding edge of the technology.

[@jackjackson5137]

Just got an untested 475A yesterday to play around with, just my luck!

[@carl112466]

So what would you recommend to replace the Tantalum Capacitors with. I hate Tantalum Capacitors they should be removed from all new electronics that are being made today.

[@lroy730]

Nice the 4XX Series is my Fave. Easy to repair, most parts are still able to get. Still have one 465. 468 was my fave.

[@EEVblog2]

Except for old units like this were the could be huge numbers of failed or failing parts

[@coriscotupi]

Here is an oddball question that just occurred: is it feasible, or practical, to use a scope's own 1kHz probe calibration output as a "signal" of sorts to be injected into say audio circuits and followed along with the oscilloscope? Yes, I know it's a square wave, not all audio circuits might be happy with it, but other than that could this be done? Can this output be used as a "wave generator" in a pinch?

[@BlackEpyon]

You see this kind of thing all the time in retro-computing channels. Any time you get something 30 years old or more, always check the inside before you power it on. Old X/Y class capacitors in particular are famous for drying out and failing in a large puff of magic smoke. Tantalums also tend to fail rather spectacularly.

[@WagonLoads]

Where is part 2? I have this scope in my basement with a bad transformer. I thought it had a toroidal transformer. Can you help?

[@davekimball3610]

Whoo hoo, that mailing address is where I was born! And just a few year's after my birthday.

[@SkyCharger001]

I sometimes heard a similar 'tick' when my parents' toaster's thermal switch disengaged. (it was an oldie even then) So it could simply mean that it's not sluggish in it's handling of overheating.

[@oorangejuce]

Nice multimeter probes!

[@joakimeliasson3244]

4:54 is the leads going to the delayline (?) up the left corner properly connected? To me they look barery soldered on, could it have been disconnected?

[@BrightBlueJim]

While those may look like bad solder joints, what you are actually looking at are individual pin sockets, which were used all over this instrument, like for all of the transistors and non-DIP ICs.

[@dewickt]

Has a shorted filter in my 475, the blue Mallory cans did not age well, after a year of use another shorted.

[@peppem94marsala]

Beautiful old style oscilloscope, not like the new oscilloscopes, all with digital electronics that cannot be repaired at all.

[@jeffreystroman2811]

Giuseppe Maggio back when I was being paid to spend someone else's money I got a 200meg 4 channel digital scope. Hardly ever turned it on after the first week because I spent more time fiddling with the scope than reading waveforms. I actually drive around with a 15meg 2 channel analog in my car, don't leave home without it.

[@gordonwedman3179]

Scope makes a popping sound but Dave apparently has no interest in finding out where that is coming from. I would have taken the cover off the HV power supply and turned it on with the room lights off. Might see an arc.

[@crapcbm]

had one of these while working, great. but began to tilt on the pots and switches ... so changed to a digital Oscar (missing the demos haha)

[@RyanUptonInnovator]

Looks like the opamps U1464A & U1464B is blown. The opamps uses negative feedback to set the negative voltages. First thing to test. It may be that those opamps are not getting the correct power voltages creating a cascading effect. You may have to trace the opamp power rails back to the fault, most likely a capacitor is shorted.

[@RyanUptonInnovator]

So was I right?

[@alanholt6535]

I use one of those at work!

[@BrightBlueJim]

The slot for the second power switch was for an option that allowed the 'scope to run from DC power. The second switch turned on the inverter.

[@DavidKHill]

Checking back here to see if this video got finished. I have a 475A that doesn't seem to be synchronizing. The timing circuit may be a fault.

[@pulesjet]

Used that exact model for years and years while in the USAF.

[@whatsstefon]

Hey @EEVblog2 do you sell all these dumpster finds? I'm after a new scope. You seem to be very lucky with finiding Scopes, TV's, Computers, etc in dumpsters. All I find are half eaten nuggets, burgers and KFC. Are you camping outside some electronics wholsaler or something?

[@VeraTR909]

Just jotting down some dope here... :P

[@pomonabill220]

That coil of cable under the CRT is the trigger delay line so you can see your trigger.

[@bitrot42]

Stuck in XY mode? No worries! I mostly use my Tek 465M as a vector display when fixing early 80’s arcade PCBs... Tek really owned the scope world back then!

[@batner]

Wow! This one I know personally!

[@TheManLab7]

8:00 "Emmet Brown" bay any chance?

[@Slartibartfas042]

LOL - This scope was built waaaayyyyyyyyy before that "Emmet Brown" figure was even created! ;-)

[@gotj]

I have one of those, with a led multimeter at the top.

[@ohmedarick1]

HI: I like does test leads hooked up to the PCB. What brand and type are they??. Anyone can advise. Thanks

[@gafaff]

Parrot Clips

[@ohmedarick1]

@@gafaff Thank you

[@pjmelect]

8.6V on the 5V rail I immediately thought of the TTL logic chips. You may be lucky though, depending on the family type LS, L, H etc it requires 9V or so to destroy them.

[@jeffreystroman2811]

Peter Mortimore greetings, I was a broadcast video tech for 20 years, factory trained whenever the sales department wanted to pick up a new product as it was required. 1970s high end electronics are really a piece of art and design. Wouldn't be surprised if that high +5 vdc rail was because nothing was loading it down. Those items weren't being told to turn on. Maybe, nice to see someone else who knows these things

[@Chris_Grossman]

The delay line has nothing to do with the delayed sweep. The delay line delays the vertical signal before it goes to the CRT so you can see what you triggered on.

[@autogolazzojr7950]

"Delayed sweep" is a somewhat ambiguous term. I think he was talking about the small delay that lets you see a bit before the trigger. A better term would be "delayed time base" (DTB).

[@cambridgemart2075]

@@autogolazzojr7950 Delayed sweep on a Tektronix scope is a mode where timebase B is delayed by the sweeptime of timebase A (often plus a fine adjustment on a seperate control); it does have a very specific meaning.

[@TheDefpom]

I think I can see a cracked solder joint on the filter cap on the right at 5:50.

[@yoramstein]

Hello Dave would add a link to your Test clips (Grabbers0 I have never seen those before and they look handy.

[@scottgfx]

An EEV cliffhanger! There's the old trick of turning out the lights to try and see where the arcing is happening.

[@Asedious1]

Wait, no "see you next time"? this is outrageous

[@redpillcommando]

Dave, you got to show us more please.

[@bobengelhardt856]

What was "the big dumpster find" alluded to?

[@bobengelhardt856]

Never mind, I found it: kzbin.info/www/bejne/j4mTfn2gpp6Aq7c

[@bertblankenstein3738]

Did you put the Aussie 240v into the Yankee 120v device? That snap could be the transformer primary side having a dielectric breakdown.

[@indrek.a]

At 5:00 you can see it's on 230V mode.

[@bertblankenstein3738]

Thank you Indrek. So perhaps the high voltage transformer for the CRT is going. That snap sure sounds like a winding that is failing.

[@BrightBlueJim]

@@bertblankenstein3738 But even more likely (since it's snapping repeatedly), it's dust/dirt forming a bridge on the PCB in the high voltage section. While these scopes often had high voltage failures, actual component failures usually blew the fuse.

[@mrnmrn1]

@@bertblankenstein3738 At 7:10 on the upper left corner you can see a neon bulb starts glowing prior to the bang. So yes, something is wrong with the high voltage supply as well. Hopefully not the transformer, because Dave won't go that far to replace it. Maybe just an overvoltage due to the overvoltage condition of the low voltage PSUs.

[@bertblankenstein3738]

Maybe someone else had the unit in 120 mode while plugged in to 240. Regardless, we await the exciting conclusion.

[@BlackEpyon]

Problem with those pouches, is that they're great if you're constantly lugging the thing around, but if you've got it on your bench, it's inevitably in the way of whatever you're stacking on top of it. I remove them.

[@proluxelectronics7419]

Anyone seen Melodysheep's TIMELAPES OF THE FUTURE. Mindblowing!!!....Sorry off topic but Science....

[@funnlivinit]

It keeps getting suggested to me but I haven't watched it. Maybe I will now.

[@proluxelectronics7419]

Well Worth the time, It will make your lifespan shink.. In a nice way....;-)

[@gregfeneis609]

All that electronics was pre-automated assembly. Probably taped up layout too. How did they get by?

[@leesa7489]

I stuffed printed circuit boards for a company Grass Valley Group, Tektronix bought GVG....hand soldering, I actually really loved doing it...

[@gregfeneis609]

@@leesa7489 I was just joking about getting by. I'm sure it was enjoyable. Many years ago, I installed and serviced machinery that did auto insert, practically at the dawn of automated assembly. It was pretty relaxed back in the day, ppl smoking and eating and drinking while they put stuff together. Not now. Everything approaches cleanroom conditions if it's not exactly cleanroom status.

[@BrightBlueJim]

Definitely hand-taped - in those days there was no layout software that could even DO curved traces.

[@outputcoupler7819]

Great Scott! Your went with 121GW for your multimeter's model number? Never noticed that before, gave me a nice chuckle.

[@BrightBlueJim]

Okay, if nobody else will bite, I will: what does "121GW" mean to you?

[@THESKYMASTER]

Why is this on EEVblog2 instead of EEVblog?

[@n2n8sda]

None of that tube rubbish, apart from the crt :D hope to see it fixed

[@EEVblog2]

Doh, yeah

[@alakani]

I have that exact same scope

[@Torogol85]

Still no part II? ;(

[@MatthewSuffidy]

I bet you thought oh the mode toggle switch is broken, but that is TOAST. No like if a rail is totally overvolting, very probably significant damage is done somewhere unless there was some sort of protection in the design.

[@maicod]

such a sudden cut off is a bit how ya doin'

[@wb6wsn]

Don't sweat any manual corrections, as even Fort Monmouth is now gone.

[@pd1jdw630]

I hope to see you resurrect the old scope.

[@daa3417]

Next up Dave dumpster find repair; better, faster, stronger, edition.

[@TheDefpom]

Both of those bad rails look to be using the same op amp, I would go there first.

[@waxore1142]

7:25 Component center screen down a little split down middle.

[@TheVirindi]

"EB"? My initials! Just like in Journey to the Center of the Earth!