Restoring an HP-120B Oscilloscope from 1961!

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  • Опубликовано: 19 июн 2024
  • I have a soft spot for old test equipment, particularly old HP test equipment. My HP-150A is my all-time favorite oscilloscope. It’s rock solid, looks gorgeous, and is stunningly good. It also weighs about nine million pounds (that’s roughly four million kilograms). I was lamenting that I needed a front-end loader to pick my 150A up to a good buddy of mine, Chris Fala, and he said “I’ve got an HP tube scope that won’t send you to the doctor for back pain.” Chris is an absolute legend and hooked me up with said scope, which is the HP-120B you see here today. It’s not currently working though, so let’s dive into it. Should be easy, right? Right?
    If you want to support the channel please hop over to Patreon:
    / usagielectric
    Also, we now have some epic shirts for sale!
    my-store-11554688.creator-spr...
    Come join us on Discord!
    Discord: / discord
    Intro Music adapted from:
    Artist: The Runaway Five
    Title: The Shinra Shuffle
    ocremix.org/remix/OCR01847
    Thanks for watching!
    Chapters
    0:00 A bit of reorganization
    2:34 Scopes!
    4:43 Testing the test equipment
    5:40 Throwing electrons at the 120B
    7:25 Deep cleaning time
    12:43 6U8 vs. 6GH8
    14:05 Testing after cleaning
    15:21 So close, let’s dig in deeper and find out what’s wrong
    17:38 Thor: “Is it though?”
    19:35 I fought the HP and the HP won…
    21:56 Battling someone else’s modifications
    24:11 Please work correctly, for my sanity’s sake
    25:48 Nailed it!
    26:48 What am I going to do with another oscilloscope?
    28:46 Derpy cat is derpy
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Комментарии • 231

  • @chrisjpf33
    @chrisjpf33 7 месяцев назад +76

    So cool to see this on your channel already! I am thrilled that it now has a much better home that I was able to provide. ;-) I had this since the mid 1990s. I used it maybe twice in all that time. It was given to me by a friend and coworker, Brad Forrester (sadly I lost touch with him since then), when I worked at VDO Yazaki in Winchester, VA. Before that, I don’t know the history. Brad, if you catch this, please tell us what you know.

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +16

      Thanks for hooking me up with the scope!
      I'm really curious how Brad had it set up with the modifications. They were clearly meant for a specific purpose, and may have been totally fine for that particular job!

    • @rfburns5601
      @rfburns5601 7 месяцев назад +9

      @@UsagiElectric I had one of these when I was a student in trade school in the late 70s. It was an H41-120B Cardiac monitor that came from the charity hospital. It had a bad 12AX7 and a 5 milliamp fuse. 5 ma fuses were used for patient protection into the vertical input. It also had the orange long persistence P7 phosphor. You can connect your chest to it and view your heart waveform only so many times before the novelty wears off. I had thought about building a slow-scan receiver out of it but never did. In the 80s I sold it to a man who had heart trouble so he could make sure his heart was OK.

    • @MrCHrisfj
      @MrCHrisfj 7 месяцев назад +1

      Maybe the long lost label that was just to the side of the screen was telling the operator to be careful of the modification?

    • @chrisjpf33
      @chrisjpf33 7 месяцев назад +3

      @@UsagiElectricjust guessing, but I would bet that the modifications pre-dated Brad's ownership of this scope.

  • @KeritechElectronics
    @KeritechElectronics 7 месяцев назад +63

    Remember, Dave: There's NEVER such a thing as "too many scopes". Period.
    It's a thing of beauty and a joy for ever - and your kitty fully agrees.

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +10

      Haha, I mean, I agree, but they sure do take up a lot of space.
      Maybe, never such a thing as "too many HP scopes"!

    • @stamasd8500
      @stamasd8500 7 месяцев назад +1

      Agreed. I only have 3 of them and feel naked. I need more. Especially since my oldest one is from the 1970s and transistor-only (Hitachi V660). :)

    • @KeritechElectronics
      @KeritechElectronics 7 месяцев назад +2

      @@stamasd8500 ha! I need a tube Tek on a scopemobile. And that won't be the end of it... if I Keri on, I'll end up like Paul Carlson!

    • @JamesHalfHorse
      @JamesHalfHorse 7 месяцев назад

      @@UsagiElectric Collecting test gear can get addictive. You have seen Curious Marc's place...

    • @WagonLoads
      @WagonLoads 7 месяцев назад +1

      @@KeritechElectronics I have a scope mobile for a 585 and one for a 475 scope.. The wheels on the 585 cart went flat on one side from sitting too long in one place. There was a metal piece near the base of the 475 cart that snapped..
      Tektronix made some wonderful items...
      I think the 475 also had a power supply problem. I thought it might have been the transformer, but I never really tested it for sure.
      My latest scope is a Tek 7904 mainframe scope.. I love scopes that have plugin modules to add extra features.. I really hope to get a spectrum analyzer for it..

  • @georgegonzalez2476
    @georgegonzalez2476 7 месяцев назад +15

    They may have had to cut some corners on the sweep and sync circuitry. Maybe Tektronix had some patents on really good sync circuits? In any case the 120 has, IMHO, a barely passable sync ability. You may notice that at some input frequencies there is some sync jittering going on. That's probably because the next cycle arrives just before the sync circuitry has fully settled down after the retrace.
    Also realize that all the neon bulbs used as level-shifters, their Krypton-85 gas has long worn out. So the bulbs are going have an unstable trigger voltage. You may want to replace the bulbs with fresh new ones. There are two in the CAL square-wave generator, those are probably jittery too.

  • @roboticus3647
    @roboticus3647 7 месяцев назад +22

    The mod you removed looks like an external sync mod, as many people find external sync to be more useful than the z channel.

    • @gcewing
      @gcewing 7 месяцев назад +2

      There's already an EXT SYNC socket on the front, though...

    • @roboticus3647
      @roboticus3647 7 месяцев назад

      Ah, I didn't see that. Even so, that's what the circuit seems to look like. ;^)
      @@gcewing

    • @gcewing
      @gcewing 7 месяцев назад +2

      @@roboticus3647 Yeah, that was my first thought as well. It's very strange. Maybe the built-in ext trig function didn't do quite what they wanted?

  • @MonkeyUnit
    @MonkeyUnit 7 месяцев назад +10

    I'm a collector of vintage HP gear. I have many of the items you are looking for to include an HP 200CDR and HP 3440a. HMU! BTW, this was my favorite episode so far.

    • @MonkeyUnit
      @MonkeyUnit 7 месяцев назад

      Fudge, my 200CDR (rack mount version of your bench top oscillator) does not have the integrated rack handles. But the 3440A does.

    • @MonkeyUnit
      @MonkeyUnit 7 месяцев назад

      It appears my comment has gotten lost in the stack. I didn't want to leave my email dangling in the wind on my channel for too long so I've removed it. If you're still interested in the HP 3440A, as a donation to the channel, let me know here.

  • @prairiedawg792
    @prairiedawg792 7 месяцев назад +5

    10:43 Use some soapy solution with the razor! Then the blade slides over the paint and it softens the residue too making it much more effective.

  • @simonkormendy849
    @simonkormendy849 7 месяцев назад +5

    7:15 That's actually a very good sign, the fact that you're able to get a stable trace on the CRT proves that pretty much all the internal circuitry does indeed appear to be working.

  • @jeremiefaucher-goulet3365
    @jeremiefaucher-goulet3365 7 месяцев назад +20

    Dave: Complains his oscilloscope is too heavy
    Dave: Gets and painstakingly repairs a smaller oscilloscope
    Also Dave: Plans to put the new oscilloscope in a rack to make it even heavier than the first. ;)
    (yes yes, i know there will be wheels)

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +7

      I mean, you're not wrong!

    • @SeekingTheLoveThatGodMeans7648
      @SeekingTheLoveThatGodMeans7648 7 месяцев назад +1

      Well, I was wondering why not put the "heavy scope" on a cart? But again that might not help when you want the scope to be on the benchtop. Maybe a cart that has a sufficiently sturdy projecting top shelf that will slip and/or pivot right over the benchtop?

    • @WagonLoads
      @WagonLoads 7 месяцев назад +2

      hmmm, moving heavy lab equipment around effortlessly always sends me back to my happy place when I saw a movie featuring a hand powered micro forklift made from a movie set camera dolly.. It was used to lift a miniaturized submarine and precisely lower it into an oversized hypodermic, which they also shrunk...
      I rewatched that movie a year ago, and as cool as it was.. There were so many technical errors(design flaws)... Well...
      10000 points to anyone who can guess what the movie was...

    • @chrisg6597
      @chrisg6597 7 месяцев назад +1

      @@WagonLoads Fantastic Voyage (1966). I remember Raquel Welch and Donald Pleasence as part of the cast, but I can't remember the others.

    • @WagonLoads
      @WagonLoads 7 месяцев назад +1

      @@chrisg6597 You get 10000 points. That movie is on RUclips..

  • @atkelar
    @atkelar 7 месяцев назад +17

    When you showed the "pin compatible layouts", I'd like to point out that some pins in one of them are shown as "not connected" whereas the ohter one has them connected. I've seen devices that use "not connected" pins as solder points on the sockets, so be careful when replacing one with the other, it might lead to magic smoke incidents; Of course that also depends on the device and soldering behind it.

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +2

      That is definitely something to keep an eye out for! Though, in this case, I think the 6GH8 is just drawn in a confusing way. Near as I can tell, the 6GH8 and 6U8 are actually 100% pin compatible. But for something like the 6CB6 and the 6AU6 there are subtle differences that don't make the swappable in all cases. Either way, I'm happy to have an original 6U8 back in place!

    • @atkelar
      @atkelar 7 месяцев назад +1

      @@UsagiElectric sorry if it came across wrong; I was not implying that you in your case had an issue with going back to the original one; The comment was intented as a bit of suplement for interested watchers who might swap out tubes based on that information. I'm far from being a tube expert myself, but after a few successful restorations and troubleshootings, this is one of the more surprising things I learned and it struck me as unusual enough to point out. I've seen both cases: unused pins for solder points and internal connections that save external wires; a quick check at the socket should be done when changing them from away from factory specs at least. And given the mods that were in your scope, I'd also double check there 😊

  • @dell177
    @dell177 7 месяцев назад +2

    When i was in high school I built an EICo 4.5mhz scope with a 3" CRT, that worked well for about 8 years but it really ran to hot and eventually the transformer cooked itself. After getting out of the army in 1970 I was working for Analog Devices as an engineering tech. when they were on Binney St near Kendal Sq.
    Sometimes on our lunch breaks a fiw of us tesks would trek down to Eli Hefferons in Summerville, ELi's was an old style surplus dealer who sold everything and anythisng from parts, electronic assemblies. and old test equipment. I ended up buying a HP120 and a HP 200 oscillator, both were rack mount inits and i hot them cheap because they didn't quite work right. The scope just needed a good cleaning and a couple of leaky caps replaced. The 200cd had a pair of tunes that were substitutes and looking at the tube manual the pinouts were the same but Rp (plate resistance) was off by 4:1. I bought a pair of the right tubes (6F6) and that fixed that. I also added a attenuation switch to the generator out put so I could attenuate the output in decade steps (copied from a PACO generator schemamatic) so now the generator worked fine for audio work.
    I still have the HP generator but sold the HP 120B to a coworker a few years later when I bought a Tek 545a scope which did a pretty good job of heating my shop. Twelve years later the Tek was getting iffy so bought a Hitachi 35 mhz scope which I still have along with a Teck 2230 analog storage scope.
    Both HP and Tek made some impressive instruments back in the '60's solid as a rock.

  • @herbertsusmann986
    @herbertsusmann986 7 месяцев назад +5

    That 100 Ohm grid resistor is known as a "grid stopper". It prevents high frequency oscillations. Same trick is used on solid state circuits on either the base or collector terminal of bipolar transistors.

  • @Runco990
    @Runco990 7 месяцев назад +9

    My Jr. High School Electric shop teacher gave me an HP 122A scope in 1978. That was the most monumental gift I ever received, and it truly kicked me off into a lifetime electronic career. ( He knew that, I think )
    I always love that graceful bezel on those scopes. You should look up an inside pic of the 122A, it's point to point wiring and an absolute work of ART!

    • @ttyR265
      @ttyR265 4 месяца назад

      Similar story for me. High school electronics teacher sold me a Tektronix 514AD scope. I still have it, thought it didn't fair well sitting in storage for a few decades. I had some ham radio guys go through it for me and it works perfectly again. I never got into electronics heavily, but I've been an enthusiast ever since.

    • @kennethdegruchy5503
      @kennethdegruchy5503 3 месяца назад +1

      My High school math teacher sensed my keen interest in electronics from speaking with my electronics shop teacher and one day summoned me to the teachers room where he bequeathed me with a Waterman Pocket Scope (s10A) which would actually display video signals acceptably. My first serious piece of test equipment and truly compact for it's time. A life time electronics career did follow.

  • @ctbcubed
    @ctbcubed 7 месяцев назад +1

    Way back in 1974, a friend and I came across some used HP120B scopes at a local surplus store. We each bought one and upon firing them up at home, neither one worked. These must have been used in a factory where there was oil mist as the internals were coated with oil. I took mine outside and used a spray bottle filled with denatured alcohol to thoroughly clean the insides. It looked almost brand new when I finished, but it still didn't work. I purchased the excellent service manual and after some head scratching discovered that the neon bulb in the sweep generator was bad. I replaced it and the scope came to life. I told my friend and he found the exact same problem with his unit! I calibrated it and it was a great for audio work. I recently gave it away and it was still working perfectly with all of the original components (except the neon bulb) from the day it was built. As far as having too many scopes, the benchmark for that is RUclipsr Mr. Carlson's Lab!

  • @rsbohn
    @rsbohn 7 месяцев назад +6

    The 120B is a beautiful device. You did a great job cleaning and restoring it.

  • @Choober65
    @Choober65 7 месяцев назад +3

    That large scope is simply BEAUTIFUL.

    • @jordanzish
      @jordanzish 7 месяцев назад

      There's a video of him cleaning/restoring it. I think 2 or 3 years old. It really is a thing of beauty.

  • @mamulcahy
    @mamulcahy 7 месяцев назад +1

    Thanks for the video. I love seeing you breathe new life into old equipment.

  • @bitteroldskunk
    @bitteroldskunk 7 месяцев назад +14

    If you hadn't noticed, some of the pins on the tube sockets looked a little cracked around a few of those sockets. You may have a few bad solder joints on those boards. Other than that, that's a sharp looking scope

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +2

      Sometimes the camera makes things look like cracks when they're really not. It definitely does look weird on a lot of the joints, but I went through and inspected them and it's really just blobs of solder, but they're all still connected nice and strong. I also went through and rocked the tubes back and forth while it was on an running to see if flexing the tube socket or PCB would cause changes in the pattern, and it didn't, so I think we're all good!

    • @bitteroldskunk
      @bitteroldskunk 7 месяцев назад

      @@UsagiElectric awesome ;] an yeah, I can agree the camera can fool the eye.

  • @jamesdecross1035
    @jamesdecross1035 7 месяцев назад +5

    What… loose an old hand-made embossed Demo label. I love to see those things!

    • @chrisjpf33
      @chrisjpf33 7 месяцев назад +4

      I said the name “Dymo” to David and he didn’t know what I was saying. ;-)

  • @qzorn4440
    @qzorn4440 7 месяцев назад

    So many sweet devices from the past. 🥰 Thank you.

  • @shalffon
    @shalffon 6 месяцев назад

    Awesome! Thank you so much for sharing!

  • @sebastian19745
    @sebastian19745 7 месяцев назад +3

    When I was young and scopes were way too expensives, I wanted so badly to have one. My projects were mostly in AF range or CMOS up to 1MHz so any scope would fit the need. Now, I have around 7 working scopes, from digital to analog with transistors, from handheld to bench and I found that I use each and every one. I recently found a pair of old 20MHz dual channel analog scopes that were broken and I just fixed one so I share your excitement. The other one needs some more troubleshooting but Christmas hollydays are coming and I plan to fix it then.

  • @phildem414
    @phildem414 7 месяцев назад

    What a hunk of a scope 😍
    Digital scopes are cool for they one shot capture, protocol interpretation and digital modes, BUT; an analog scope is a special connection to the signal.
    I love both!

  • @MsFireboy2
    @MsFireboy2 2 месяца назад

    Thanks for posting very informative.

  • @Zadster
    @Zadster 7 месяцев назад

    This is why I always add a note inside equipment that I have modified or repaired - especially my own! Not just stating what was changed, but why. You *might* find that tube you replaced was a factory upgrade or mod. Looks like you are setting up a museum for HP test gear from the generation immediately before CuriousMarc's collection. And that is a really good thing!

  • @jdolecki100
    @jdolecki100 7 месяцев назад +4

    It’s simple you need to make that room bigger.

  • @georgegonzalez2476
    @georgegonzalez2476 7 месяцев назад +5

    Nooooo! I've interfaced a Selectric to a computer. Around 1980. It took a large amount of hardware and software. The Selectric basic mechanism wasn't designed with computer control in mind, so it is difficult to interface. It's possible if you're not careful in sending it pulses, to lock up the shift mechanism. Have a month or two and a full service manual.
    Also it's in no way an ASCII machine, so you need a bit of coding to map ASCII to tilt and rotate signals for the golf ball. And it won't accept a full-speed serial stream, you have to wait after each character for a handshake signal. And there is no handshake signal if you're shifting to upper-case when it's already in upper case, so yo have to special-case that situation or the whole thing locks up. Not a lot of fun. Good print quality though.

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +2

      The good news with the Selectric Composer is it already has the six solenoids and switches set up to type and interpret what is being typed, but as you said there's still a ton of serious hurdles to overcome. The marriage of mechanical and digital is a finicky one, and getting that thing working reliably as a data terminal is going to be a proper challenge! But, I have to get it working reliably as a Selectric first. We have a serious mountain to climb for sure, but I think it's going to be a fun one!

  • @macgvrs
    @macgvrs 7 месяцев назад +2

    Good job repairing that scope. That was a tricky one. When repairing vintage radios I have encountered bad Sprague caps. It is possible there are commercial higher quality caps being used in test equipment. Just wanted you to know you can't always rely on the fact they are Sprague caps.

  • @jamesdecross1035
    @jamesdecross1035 7 месяцев назад +1

    Now you've fixed it your challenge, should you choose to accept it, is to recreate those beautiful on-screen patterns. Go for it!

  • @AndersNielsenAA
    @AndersNielsenAA 6 месяцев назад

    Wow that 120B is beautiful! The CRT bezel really makes it shine!

  • @simonkormendy849
    @simonkormendy849 7 месяцев назад

    Cool, as it just so happens, I have an old Oscilloscope stored away in one of my cupboards, it's an old Telequipment D33R Tube Oscilloscope, it's currently not working and needs a new, or second-hand CRT, plus some restoration work to get it going again, it's a great restoration project.

  • @ashraf9472
    @ashraf9472 7 месяцев назад +1

    Thanks for more power!!

  • @robertlinder6414
    @robertlinder6414 7 месяцев назад +3

    Flashback to 1976 High School electronics shop

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +2

      I think high school electronics classes should still use old analog scopes, they're wonderful little tools!

  • @pac1085
    @pac1085 7 месяцев назад +2

    I'd say the HP 651A Test Oscillator meets the rack mount requirement and the aesthetic, but it's a bit newer (1965) and transistorized. They can be had super cheap though. I bought one in the hopes of using the case for it to fit my HP Barney Oliver amplifier, but it wasn't quite right... so it just sits here on a shelf now. lol

  • @rickhuang4493
    @rickhuang4493 7 месяцев назад +1

    The PNP transistor and the Zener diode forms a basic current follower. The zener is the voltage reference and the PNP transistor create a voltage that's close (600mV delta) to Zener's voltage with higher current capability. This is essentially the same as a current follower circuit that uses a NPN transistor and a Zener diode that is more commonly used today except with the use of PNP transistor, the whole circuit is a mirror of the one that uses NPN transistor. Hint, the placement of the ground is confusing. Redraw the circuit by putting the ground at the +19V rail will make the analysis easier.

  • @matthewspence3251
    @matthewspence3251 7 месяцев назад +1

    Beautifly simple scope - I used one of these for my phd in 1992, triggered by the laser pulses … measurements of molecular dynamics photon counting in a pitch black university basement except for the glow of the tubes and an ibm 5150 for data logging.

  • @Charlottesville798
    @Charlottesville798 7 месяцев назад

    I've got a 1974 mini portable oscilloscope in a brown leather case im trying to resurrect, great video!

  • @restingsmirkface
    @restingsmirkface 7 месяцев назад

    Nice work!

  • @mm-hl7gh
    @mm-hl7gh 7 месяцев назад

    using this old hp gear to get the old bendix running would be aweseome !! :D cant wait !

  • @JCWise-sf9ww
    @JCWise-sf9ww 7 месяцев назад

    I seen a similar thing happen with a solid state Telequipment Scope, spent days trying to TS the problem, replacing some caps, in the end the bias pot for the schmitt trigger need calibrated by using another Scope. Then the triggering stayed locked in when changing frequencies on my signal generator.

  • @jeromethiel4323
    @jeromethiel4323 7 месяцев назад

    The college i attended in the mid 80's was still using a gigantic vacuum tube o-scope, as it was the only scope they had that could do two very important things. One, was to generate a transistor family of curves. Two was that you could hook a land camera to it, and take a picture of said transistor curves, and develop them yourself darn near instantly.
    Bonus, was that you could actually draw on the photo to pick your bias point for that particular transistor.
    That o-scope had to weigh at least 200 pounds. It was 3 feet deep and 2 foot x 2 foot across the front. You could only move it in it's wheeled rack.
    Amazing how well that o-scope worked. We had regular old analog, transistor based tektronix scopes at each workbench, but you could not do transistor curves on them. At least not with the equipment the school had on hand.

  • @drrenard1277
    @drrenard1277 7 месяцев назад

    I worked for Litton industries before acquired by Northrop. I worked in Aero department but I've seen so many of Litton old stock in storage

  • @skfalpink123
    @skfalpink123 7 месяцев назад

    My phone line reconnected, I can FINALLY watch the second half of this video!

  • @Ihamfp
    @Ihamfp 7 месяцев назад +6

    I have an HP 8405A "Vector Voltmeter" (well actually, just the case... wanted to use it for an homemade amplifier), with a very similar style, handles and all, and with the stackable plastic feet this 120B seems to be lacking. It fits perfectly on my other 19" HP things ! If you need I could model them in CAD and send the files for 3D printing copies.

    • @borisj4054
      @borisj4054 6 месяцев назад

      Have a full working hp vector volt meter with all the accessories. Very useful instrument used with directional couplers to measure insertion losses or used to measure electrical length of cables.

  • @fernandonovoa3261
    @fernandonovoa3261 7 месяцев назад +1

    Muy buen trabajo !!, saludos.

  • @annieworroll4373
    @annieworroll4373 7 месяцев назад

    One of these days I want a classic unit like this.
    My Hantek handheld does the job I need it to do, but there's something about the look to these beasts.

  • @mikegLXIVMM
    @mikegLXIVMM 7 месяцев назад

    I used to have an HP 130C scope.
    Same crazy tube/ Transistor mix.

  • @50shadesofbeige88
    @50shadesofbeige88 7 месяцев назад

    Reminds me of Curious Marc. Very cool video. I love old HP gear.

  • @FJL4215
    @FJL4215 6 месяцев назад

    11:28 Removing that big black 450KHZ sticker made it 10x more beautiful. Satisfying.
    The zener + transistor was a nice simple regulator circuit. When the output voltage reaches the zener voltage minus the Vbe of the transistor, the zener diode starts to conduct and starts turning off the transistor. The resistor from the -150V makes essentially a current source that provides the base current to turn on the transistor.

  • @alanpecherer5705
    @alanpecherer5705 7 месяцев назад +5

    The 6U8 turned out to be somewhat of a problematic tube in many applications. They have a propensity to heater to cathode leakage. This may or may not show up on a tube tester, but is exactly the kind of thing that will throw noise on your trace and contribute to instability in your H-sweep. Exactly the issues you have. That is why, I'll bet, that they were substituted out in your scope as-found with allegedly superior types. Bottom line, it's kind of a defective design tube. They were reasonably popular tubes in old TV sets and if that is the source of your bag of 6U8's, all of them could be hinky on H-K leakage side. Before going nuts searching for a defective component in your scope, I would invest

  • @jurjenbos228
    @jurjenbos228 7 месяцев назад

    I just love that the litton looks like a washing machine. This form factor is pretty unique.

  • @nickk6109
    @nickk6109 7 месяцев назад

    That regulator and zener could be a clamp on the regulator to stop it from spiking over, or, it could be an early shunt regulator providing a low noise power supply by having a constant current bypassing through the zener (would need to see what’s elsewhere on the schematic.

  • @JohnDlugosz
    @JohnDlugosz 7 месяцев назад

    re the thumbnail: Wow! I had that exact model 'scope, too! I bought it on-line in the mid or late '90's -- not sure if Ebay was around yet, but something like that. Around $80 IIRC. The rack-mount ears had been cut off. In the early '00's, after getting married, I gave it to a friend who collected oscilloscopes (he also had *every* Star Trek novel paperback).
    I suppose there were quite a few of these still kicking around, since they would just keep on working.
    Update: seeing it in the video, it's not the identical model.

  • @justicelut
    @justicelut 6 месяцев назад

    Good work. You can never have enough scopes! IMO!

  • @KameraShy
    @KameraShy 7 месяцев назад

    This vintage electronic equipment was designed when nominal voltage was 110. Now it ranges from 124 to 129, at least in my area. If a vintage device is randomly blowing its fuse for no apparent reason, I am wondering if voltage fluctuations and spikes could be a factor. Maybe monitor the power line or use a variac. This may be particularly important for precision test equipment - to get correct readings - versus something like audio equipment.

  • @vincentguttmann2231
    @vincentguttmann2231 7 месяцев назад

    I'd go ahead and ask CuriousMarc if they have something for you, they're like THE masters of HP equipment.

  • @TheHylianBatman
    @TheHylianBatman 7 месяцев назад

    Don't forget the power supply for the mobile test rack! I wonder what that would be.
    Also speaking of not forgetting, what about the other old HP equipment that's been waiting for work for a couple of years? You could restore those, or, if they're not getting touched any time soon, you could move them out of the room to free up space?
    I love that you're just collecting old equipment. Someday, you're gonna need a bigger space!
    I can see it now, in 10 year's time: "Now opening, the David Lovett Texas Museum of Technology"!
    Featuring wings on cars, Japanese tech, Centurion, and vacuum tubes, of course!

  • @neilthomas6042
    @neilthomas6042 7 месяцев назад

    Interesting video, glad you got it working. Cute cat having a lick at the end; adorable.

  • @WagonLoads
    @WagonLoads 7 месяцев назад +1

    The Tektronix TM506 is a rack mount system for solid state plug in modules..
    I don't know if there is a vacuum tube equivalent to it though..
    But that would be a starting point in form factor search possibilities..
    By the way.. I have a Tektronix 585 laying around somewhere...
    I think it had a problem with the power supply...

  • @computeraidedworld1148
    @computeraidedworld1148 7 месяцев назад

    I adore your channel, and was just curious, where did you learn your way around schematics? Reading them and finding how to pin point possible places to check.

  • @radarmusen
    @radarmusen 7 месяцев назад

    That bendix teletype carrier looks like it are able to knock things off the desk from a good distance.

  • @Renville80
    @Renville80 7 месяцев назад +1

    When removing old adhesive, I find that soaking it with isopropyl (sometimes with a rag or towel laid on top) will go a long ways towards softening it to where it will come more easily.

    • @SeekingTheLoveThatGodMeans7648
      @SeekingTheLoveThatGodMeans7648 7 месяцев назад

      Yes; another possibility is naptha (cigarette lighter fluid). "Keep away from fire, flame, or spark."

  • @JamesHalfHorse
    @JamesHalfHorse 7 месяцев назад

    There is a reason that big equipment had optional (but not really) rolling stands. There are some Tektronix ones I hope come into my possession.

  • @johngalt7382
    @johngalt7382 7 месяцев назад +2

    As the zener conducts it positive biases the base of the pnp (off), held on with the 15k resistor to the negative supply, establishing a nfb loop, increasing the v drop to the ground.

    • @paulmoir4452
      @paulmoir4452 7 месяцев назад +1

      It also looks weird to us who are more used to power NPN devices. It's just the familiar pass transistor linear regulator topology upside-down. The pass transistor is on the bottom 0V rail rather than the top positive rail.

    • @johngalt7382
      @johngalt7382 7 месяцев назад

      @@paulmoir4452 I'm guessing that it dates to the pnp germanium era, before npn silicon power devices were common, but it is exactly that.

  • @gd2329j
    @gd2329j 7 месяцев назад

    Looks like a old external sync mod .
    Used with rf sweep generators or possibly part of a diy curve tracer .

  • @Renville80
    @Renville80 7 месяцев назад

    Just putting this out there, since you mention the Model 15 teletype... see if you can find one that was modified for use by deaf people as the wiring harness was greatly simplified to have just the power and two pairs of cables (one would produce a Baudot serial stream from the keyboard and the other would be a similar Baudot stream to drive the printer). Both data cables would go into a box that would have an acoustic coupler for a telephone handset.

  • @colinstu
    @colinstu 7 месяцев назад +1

    I hope you can source the rest of that HP gear, that would be a sweet setup

  • @pfitz4881
    @pfitz4881 7 месяцев назад

    I see you have a Marantz receiver!!! I wish I had the one I owned in the late 70s.

  • @maskddingo1779
    @maskddingo1779 7 месяцев назад +2

    7 scopes seems like a pretty ideal amount😂

    • @trevorvanbremen4718
      @trevorvanbremen4718 7 месяцев назад

      Makes me feel soooooo unworthy... I only have three!

  • @barryyoung6159
    @barryyoung6159 6 месяцев назад

    What A lovely thing 🙂

  • @byterock
    @byterock 7 месяцев назад

    A one point you had a classic Fuzzy Worm, trace. It is usually caused by one wire crossing a wire or pressing close against it. That mysterious white wire could cause that.

  • @tony359
    @tony359 7 месяцев назад

    Amazing repair and restoration! So we don't know why that modification was done in the first place? Weird!

  • @jrhalabamacustoms5673
    @jrhalabamacustoms5673 7 месяцев назад

    Yay, an oscope that's basically the same age as me, its prettier too! Nice find!

  • @EIs4Excellence
    @EIs4Excellence 7 месяцев назад

    Hey, it was cool to meet you in Maryland. As far as your question about what to do with another oscilloscope... You could always give one to me! I just have a cheapo $10 handheld jobbie :(

  • @mathewmcgill6266
    @mathewmcgill6266 6 месяцев назад

    I use to use that scope.

  • @StefanWolfrum
    @StefanWolfrum 7 месяцев назад +3

    Wow, such cool equipment from HP! Love ❤ it!! Makes me think about _my_ lab equipment … 🤔 😂 💸

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +2

      Thanks!
      I have a soft spot for old test equipment, especially HP stuff, and this one was right up my alley!

  • @RPrice_OG
    @RPrice_OG 7 месяцев назад

    I'd love to have a rack full of vintage test equipment like I had back in the 70s/80s but I don't have the space for such a thing. I know my Siglent does more in much less space but it does not look nearly as cool.

  • @RobsonWilliam82
    @RobsonWilliam82 7 месяцев назад

    "Wavy sine wave". That's a true sine wave! 😂

  • @simonkormendy849
    @simonkormendy849 7 месяцев назад +1

    The level of serviceability shown with this Scope is something that seriously needs to be brought back into consumer electronics, electronic equipment manufacturers these days try to build stuff as cheaply as possible to maintain their healthy profit-margins, which is a bit unfortunate, there's deliberate "planned-obsolescence" as well, most modern electronic devices end up on e-waste piles in India when they become obsolete, and, or, defunct.

    • @PCFixer
      @PCFixer 7 месяцев назад

      Oh, man, this comment is ALL MY FRUSTRATION with modern technology, arrrrgh!!! I miss the days when everything was serviceable and repairable, not held together with locking tabs!!!

  • @TheAtomstrike
    @TheAtomstrike 7 месяцев назад

    current through r363 opens the transistor. When sufficient voltage appears on the red wire, current begins to flow through the zener and this current closes the transistor. In this way, a constant voltage is maintained on the red wire

  • @LeonDerczynski
    @LeonDerczynski 7 месяцев назад

    hey, that cut at 6:58 was subtle! not bad

  • @milanzizka4636
    @milanzizka4636 7 месяцев назад

    The cat 😼is great after all! 👍

  • @clyde3013
    @clyde3013 7 месяцев назад +2

    ooh more big hp brick stuff!

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +1

      Every once in a while I need my vintage HP test equipment fix!

  • @joshj88
    @joshj88 7 месяцев назад

    I really think you should use Hllrl as your hello. I know it’s silly but I love your modified hello world

  • @ozzie_goat
    @ozzie_goat 7 месяцев назад

    I need to show my scope some love now...
    I have a Philips PM3240 from God knows how long ago

    • @dan3a
      @dan3a 7 месяцев назад

      Nice! Got its little brother, the PM3055, wonder how long it'll last before I'll have to repair it though. (Maybe that's why you never have enough osciloscopes!)

  • @AttemptingAstro
    @AttemptingAstro 7 месяцев назад

    All that VC troubleshooting and it was a resistor....well honestly, yay. At least that's what it was and you found it haha

  • @nickolaswilliams935
    @nickolaswilliams935 7 месяцев назад +1

    6U8 and 6GH8 are interchangeable in nearly all applications, but in my experience the GH doesn’t last as long. Remember that they came out near the end of the vacuum tube television era, so quality wasn’t as good and most of the circuits they were used in pushed them to their design limit.

    • @HimmelsDaemon
      @HimmelsDaemon 7 месяцев назад

      I think Mr. Carlson spoke of them at least once, or something similar with the same triode/pentode difference. That comment about towards the end of an era sound familiar, but might be combining things, later part of what you said not included. Would have to scrub projects from the last year to three, I think it was of relatively recent memory.

  • @MaxWithTheSax
    @MaxWithTheSax 7 месяцев назад

    I believe the modification might have been to create a marker dot on the external trigger pulse.

  • @emmettturner9452
    @emmettturner9452 6 месяцев назад

    I have a AN/USM-338 “portable” scope that is the U.S. Marine Corps version of an old HP 1707B scope from the mid-‘70s. I have no idea how to use it! I was hoping to get an old analog CRT scope so I could get the eye pattern when adjusting CD lasers but I’m told I need at least 100MHz and this is 75MHz.

    • @emmettturner9452
      @emmettturner9452 6 месяцев назад

      It is, of course, able to be battery-powered and supports AC or 12v DC operation. I guess that’s what makes it a portable military scope. ;)

  • @brianclimbs1509
    @brianclimbs1509 7 месяцев назад

    How did the knob turn on it's own at 6:58?

  • @VorpalGun
    @VorpalGun 7 месяцев назад +1

    Have the wang writer in the main house area, so you can use it to write video scripts!

  • @ebayscopeman
    @ebayscopeman 6 месяцев назад

    OMG a HP-150 Oscilloscope. HP's first plug-in oscilloscope close to disaster, they recalled and repaired a ton of these for flaky PCB's.! Bumblebee capacitors and all. I bought one of these at a hamfest when I was in engineering school. I had a couple of plugins for it. If anyone finds one of these that has all of the front panel painted with baby blue Rustoleum paint and painstakingly redone lettering it was the one I had. I have not seen it since or one like it) I sold it decades ago. If you have it I would like to know! W3OHM

  • @coldfinger459sub0
    @coldfinger459sub0 6 месяцев назад

    I love old test EQ but it takes so much bench top & shelf when you start getting too much of it.

  • @emilschw8924
    @emilschw8924 3 месяца назад

    Old school beauty trumps modern electronics 😂

  • @nickcaruso
    @nickcaruso 5 месяцев назад

    phenolic pcbs... when did fiberglass come into use?

  • @gbowne1
    @gbowne1 7 месяцев назад +1

    Must be me or something because the ol monster 150, either the trace or the graticule is not perfectly horizontal. other than that, nice 120! :)

  • @alanpecherer5705
    @alanpecherer5705 7 месяцев назад

    The other thing you could do, at zero cost, is to put the oldest cruddiest looking 6U8's in the scope for the H-sweep and the V amplifier and see if the problems get WORSE. THAT, by the way, is one reason why you might want to preserve the silk screening on the exterior of the tube when you clean them.

  • @antoniodias2776
    @antoniodias2776 6 месяцев назад

    Excelente.

  • @timothystockman7533
    @timothystockman7533 7 месяцев назад

    I had an HP 120B at one time!

  • @justinpakarno4346
    @justinpakarno4346 7 месяцев назад +1

    The Litton computer looks like a laundry machine.

    • @UsagiElectric
      @UsagiElectric  7 месяцев назад +1

      Isn't it fantastic!

    • @CATech1138
      @CATech1138 7 месяцев назад +1

      i though 60s roll around dishwasher

  • @anvz6
    @anvz6 7 месяцев назад

    I think the mod was for adding external trigger. Probably the previous owner needed it and thought that he never will need z axis input then used it's jack.

    • @SeekingTheLoveThatGodMeans7648
      @SeekingTheLoveThatGodMeans7648 7 месяцев назад

      Another possibility is going back one stage from CRT blanking signal to get a positive=more intense/negative=less intense beam response (and amplified, and without a high voltage pulse coming from the input) to Z axis. I did this on an old Conar 250.