HP 7044A X-Y Recorder Restoration

[@graemedavidson499]

A chart topping plot - high tension, a power struggle, getting locked up, some good travel, a twist with pen testing, catastrophic break down, some more tension and the hero saves the day!

[@CuriousMarc]

So many unexpected twists and turns in this restoration! I need to add chapters…

[@unmanaged]

marc whats the outro song ? also can I send you one of the first DSO scope addon that is all ds logic ?

[@bobbybiggs4348]

Genius comment. Well done.

[@MichaelEhling]

Is it just me or does anyone else look forward to the elevator music explanations? This week: adding op amps!

[@RicoD5]

Marc makes the effort to involve us in the repair by explain the detailed workings of it all. The elevator music is my trigger to sit back and enjoy the trip.

[@jurjenbos228]

Watching this channel for a while is half an EE education.

[@marcoaurelio4903]

I find the end part very touching as a latin american undergrad student in engeneering when you talk a little about your routine in the lab... IDK why but i find it "cozy"??? I love to hear older engeneers talk about their day-to-day work... continue with your work, which will certainly inspire many undergrads around the world!

[@CuriousMarc]

Aw thanks!

[@tychosis]

As an old EE, I'm really glad to hear that students are watching this stuff. Frankly, this is what a lot of *real* engineering work looks like. I sometimes feel like the curricula in schools doesn't always prepare students for it... I work in integration and a lot of my work is "here's a thing someone else built, and it isn't working and we don't really know how it's meant to work. figure all of that out and let us know when you're done." It's challenging but also rewarding in a way that working from a brand new clean-sheet design can't match.

[@rot_studios]

100% agree with the extortion on old service manuals.

[@Derpy1969]

The sharpie pen tip fix is the truest example of finding a modern solution to a lack spare parts.

[@alnwlsn]

I got my hands on one of the HPIB plotters for the first time recently - the electrostatic paper holder is just crazy, something that I surely wouldn't have thought of if it hadn't already been done. And this was in 1979 (and as I understand it, was used for quite a while before that)

[@CuriousMarc]

I’m amazed too at how well it works. It’s like the helicopter - it shouldn’t work but it actually does!

[@benjaminhanke79]

I didn't know that they used an electrostatic paper holder. I only knew that the later HPGL Plotter (7550? the A3/A4 model ) used vacuum to hold down the moving paper.

[@soloflo]

@@CuriousMarcquantum tunneling shouldn’t work either 😂 crazy universe

[@wizardofeyes]

Thank you very much for the video and the operation/service manual. I have one of these plotters "Awaiting implementation". If it doesn't work when I turn it on, I'll have your experience as a guide!

[@CuriousMarc]

That’s the spirit! Wishing you the best of luck with your HP instrument resurrection!

[@tekvax01]

Excellent Repair again, as always! You have one of the best Electronic channels on the KZbin! You content is always the positive height of my day. Thank you again Marc!

[@projectartichoke]

I'll second that! Best electronics videos anywhere. I always learn so much with each new video and such a positive, can-do attitude is truly appreciated.

[@Electronics-Rocks]

I used to be a printer engineer back in the 80's & see you broke the carrier after tightening. You should change the loading in small steps. Then get the unit to do a full travel & repeat check with adjustment. As the loading of the wires varies. Keep going love your work with Ken!

[@gvii]

I always love these videos. Seeing how this older high precision equipment works. Plus, you get a nice tutorial on various circuits along the way. And Holy Hell, do I miss proper manuals with theory of operations and schematics. Yes, I know a lot of devices today would require a schematic the size of a city block and are often nearly impossible to repair for the average person due to microscopic components and conformal coatings, but still... I do miss them. Lol.

[@projectartichoke]

There is a lot to be said for the old days. Things were not only repairable but understandable as well. I think it's always best to use the simplest technology possible to accomplish the goal at hand taking into account cost, size, and performance. Easier said than done though!

[@gorak9000]

Meh, for surface mount parts, we have microscopes, and for conformal coating, we have hot air and tweezers. The sucky part is spending a week tracing out the components to draw out your own schematic.

[@crystalcandles752]

The circuits stuff is why I watch too! My experience is with cars and it's the same with electronics. You get to a certain year and working on it is a totally different animal

[@tocsa120ls]

Haven't heard a uA741 described as *better* than anything in a while ;)

[@InssiAjaton]

Clearly the main improvement the uA741 introduced, was the correction of latch-up of the uA709. Well, for some people it also may have been the freeing of need to add external frequency compensation components. On the other hand, the ‘709 was faster in situations when the application did not need the compensation, i.e. when the loop gain was high enough. Same situation as that between OP27 and OP37. But frankly, I changed from uA709 to uA741 as soon as I had tested it was “better”.

[@graemezimmer604]

Thank you Marc, very interesting! Many years ago I ran thousands of plots whilst carrying out EMC Certification tests, so have always wanted to explore the internals. I remember that we eventually moved to a conventional printer when pens became so hard to find.

[@skfalpink123]

As someone who recently an HP-16C calculator, it's easy to see how addictive HP hardware is. I'm eyeing up my next fix already

[@projectartichoke]

Always a joy watching you restore these wonderful old devices to their former glory.

[@SuburbanDon]

I worked at Ford Aerospace in the eighties and part of my job was shuttling test equipment around for calibration etc. i know full well how heavy HP and old Tektronix test equipment is. I remember this plotter well.

[@-r-495]

Marc, thank you so much for sharing the documents you acquired and the many pages you have had scanned by the National Archives. You’re not only working with historical artefacts but also making sure anyone can easily access the information that belongs together with them. Basically growing the understanding and shared knowledge about our technological heritage. Chapeau!

[@-r-495]

I have a soft spot for line writers. The ones built by Jaquet used to be a de facto standard for recording processes data by the means of electromechanical marvel but quite the nuisance when they needed the time setting twice a year.

[@ronc9743]

In the early 1980's I used to build Solid State replacements for vacuum tubes that were getting too expensive. We potted them in JB Weld for strength.

[@CuriousMarc]

Which proves again that you can repair **anything** with JB Weld. Stick pins in a block of JB Weld, flip it over and plug it in the socket, I’m sure it will replace your fried microprocessor chip just fine!

[@antronargaiv3283]

We used to use something very sikilar when I repaired Model 33 Teletypes in college (frustrated programmera used to pound on the plastic covers, breaking them). Miller Stephenson epoxy and 12 gauge solid copper wire as filler and repair staples.

[@jurjenbos228]

Brilliant explanation of the servo loop. Thanks. BTW what an amazing device. I used plotters in that era, but I didn't know these existed already then.

[@RobSchofield]

@ <a href="#" class="seekto" data-time="2330">38:50</a> - big day for me when I also did the same curve - a very satisfying result after a *lot* of *really hard work*. Marvellous video, really enjoyed it!

[@CuriousMarc]

Yay a fellow laser diode maker

[@randylemn]

For your broken plastic part if you really need it to be strong you might think about Hysol 9430 High strength Epoxy. Will not break.

[@CuriousMarc]

Thanks, I didn’t know about it but I’ll give it a shot!

[@bitdiddle1]

Bravo! Love those HP analog servo loops.

[@jobkneppers]

Marc, the used bearings are the split type which means you press them in after the part is manufactured. The size of the hole for pressing determines the fit on the shaft. They work excellent and will last a lifetime when mounted correctly. Best! Job

[@TrboRadio-rc4ol]

<a href="#" class="seekto" data-time="317">5:17</a> p.m. on July 20, 1969, the eagle has landed. <a href="#" class="seekto" data-time="690">11:30</a> p.m. Neil Armstrong stepped on the moon. In Argentina, Brazil, Uruguay and Spain means happy friendship day! Runs the Voice!

[@projectartichoke]

Watched it live on TV when I had just reached the age of 7 years. I'll never forget my whole family there and the feeling that we could do anything if we just set our minds to it.

[@TRBORADIO]

It was the 55th anniversary, I was thinking some at news or events but looks like no one remembers 😂

[@jlwilliams]

A very satisfying episode! The all-electronic projects are interesting, but there's something tangible about things with moving parts. I really appreciated the demo at the end showing how the instrument was used back in the day.

[@henrikhalle8305]

Saw the hole video. Liked it. Understand absolutely nothing of what was happening. But I love when there is people that knows something to a high level.

[@EinChris75]

Amazing... I saw the 12 Volts at <a href="#" class="seekto" data-time="1160">19:20</a> ;-) (Just for the algorithms.) I always enjoy those repairy things... so much to learn from them. From concepts of electronic mechanical engineering, to bug tracking and to conducting real repair work. Nowadays too many things are just thrown away, because they are unrepairable or no one wants to do it even if possible.

[@CuriousMarc]

Great use of your imagination!

[@electronicgarden3259]

I got one of those in working condition. Plus a smaller, 7035, maybe. Fascinating machines.

[@RicoD5]

What a great restoration again Marc! Enjoyed it to the last second. As a former parts repair engineer back in the 80’s, I still like fault finding and repair stuff. And It’s a comforting thought that even the best specialists in the field have the occasional mishap during the process 😊

[@Spookieham]

For once I beat Marc! When I saw the jump of the Y axis at the bottom my first thought was the resistive track has been lost, it's gone OC and the loop is now open. Another great video showing just how good test gear of that area was.

[@simonpritchard472]

Me too -- not knowing about the Op-Amp potential issue first think of a 'simple' explanation!

[@dwipf1851]

I used an X/Y recorder in the first years of my Ph.D. project collecting electrochemistry data (cyclic voltammograms, essential i-v curves). The sound of the x/y recorder buzzing from 60 Hz pickup is indelible memory. I kind of miss that tactile data collection process.

[@brianclimbs1509]

Thanks for another great video. That was some really enjoyable troubleshooting to watch.

[@trex70]

Funny is. Some years ago you had no chance to repair or restore plastic parts of these like machines. But with modern 3D printers no problem anymore.Historic machines with wearing parts can be brought back to funktional.

[@MLX1401]

You know, that last setup would melt any heart 🔥

[@milloons2847]

Thanks for the hands on course on feedback control, also for the pen tip tips. Regards!

[@SubTroppo]

HP plotters were the first 'printers' I had anything to do with - used for monitoring the swing of the dredge 'New Jersey' [launched circa 1927?] cutting a turning basin for a port in Saudi Arabia. It was linked to a Motorola Mini-Ranger navigation system with the master antenna being raised and lowered on a "flag-pole" to suite the state of the tide. At certain states of the tide the Mini-Range signals "bounced" off the sea-surface and I was required to climb out on the gantry to raise or lower the master unit to achieve reception.

[@antronargaiv3283]

I'm a huge fan of JB Weld. Nice for all sorts of repairs and seems to hold up well over time and under UV exposure.

[@aaronr.9644]

Very cool little demo at the end! I thought this was more the type of stuff physicists would work with. I am surprised you got a chance to work with this in your engineering program. Really cool!

[@kurt9232]

Very good explained. Thank you so much. I understood a lot and learned much again.

[@kurt9232]

Meaning the electronics part. The rest ist is also very interesting. Enjoyed it a lot.

[@TeslaTales59]

Now that was a dedicated repair! Great work sir.

[@rolfdieterklein]

excellent video, I still hav a digital plotter 281 (multicolor) around from those days, maybe have to check if it still works and repair if necessary (cap?) -- was great at that times, and even fits to a lecroy scop for screendump. The nic ething about the 281 was the automatic change of the pens, and it has holders for standard ink pens used anywhere refillable--- really make me motivated to look after this device in my storage. Form my father company I had a still older yt plotter on a wheel but due to a water disaster had to throw awy some years ago

[@ronjohnson9690]

I couldn't find a dull moment on this level.

[@TimoNoko]

There was one benefit on servo-loop over stepper motor. It is self-correcting. If the stepper goes out of step, the sync is gone foreveeer.

[@jamesbrewer3020]

Another great one!

[@darkwinter7395]

Wait - you have 2N3904s in your *garden* ?!?!

[@CuriousMarc]

So I can pick’em up just when they are ripe!

[@CoreyStup]

Love the pen rehab details!

[@daveevans9809]

quality nerd candy yet again - thank you.

[@mariodistefano2973]

Fantastic restoration, MARK!!!

[@michaelmiller641]

Fascinating!

[@zh84]

Back in the 1970s I saw a science documentary where the laboratory was using an XY plotter like this. I remember the commentary explaining, as the chart was drawn, that the nearer the output was to a perfect circle, the better. I can't remember what they were testing, but it has often occurred to me since that this was something very difficult to judge by eye.

[@Hogla287]

I just built one of these homebrew out of 3d printer parts (Mine has a dual pen write head though!). Drawing machines are tons of fun

[@wdavem]

And how many of these problems were shipping damage? Your repair of the plastic and old dry pens were amazing! Never underestimate the destructive chaos that is shipping damage! Senders should always remember that packages that weigh anything at all may end up on the bottom of a stack of heavy packages, so they could be crushed in unusual ways with ridiculous force. Shock damage is often nothing compared with crush damage. I've seen heavy rack equipment bent into a slight s-shape even (recently). I had to repair the problems from that, broken boards and of course chassis alignment issues. Machines in the best condition you'll ever see can be turned into parts machines even if they are packed kind of well.

[@bobcarter6143]

Took me back. Used one of these in my final year degree project back in 78..L..😊

[@oelschpm]

Marvelous Marc solo is solid but I prefer when more than one Avenger is on the scene.

[@TheDefpom]

My guess its the Y op-amp, I see the old op-amps failing quite a bit in old equipment, always one of the first things I suspect as a result.

[@MeriaDuck]

That use before date being highly specific and yaiks many decades in the past 😂

[@bigsarge2085]

Always interesting!

[@erickvond6825]

Very nice!

[@leon545b]

I have a 9872 plotter which somewhat works, which is of about the same vintage. I want to make it play with my 9810A calculator! It's on my list...

[@gorak9000]

I've seen these X-Y plotters, and never thought about how they were used - basically the old timey equivalent of a .csv file and pyplot :) That's actually pretty nifty to plot IV (or LI) curves directly, but the analysis by hand on the paper chart would be slightly annoying

[@KallePihlajasaari]

Yeah, interns would be tasked with reading the values off the curves with a ruler to enter on punch cards for further computer analysis if required. Now we are blessed with analogue to digital converters at 6 to 24 bits of resolution that is fed directly into a digital process loop.

[@chrisingle5839]

I remember one of those in the movie "The Andromeda Strain", at the part where they are searching for the location of the capsule.

[@I967]

What an interesting instrument. Thank you for another inspiring video, Marc.

[@SubTroppo]

This video needs a very pro-active cat to give it some vim. Those movements at the start would surely have provoked a violent reaction. ...And yes I've been watching far too many cat/printer videos.

[@Orbis92]

I still feel sorry for destroying one of those old HP plotters, when we had to cleared out a storage room at the big company I did my apprenticeship at. Sadly I wasn't allowed to take it home, so I disassembled it to parts to get a look at how it works, and than throw it away.... :(

[@MarcelHuguenin]

A master class once again, great restoration Marc and topping it of with the demo referring back to your engineering classes was just great.

[@joegee2815]

These videos are so calming, except when you replace the wrong op amp! Grrrr!

[@davidbowie1996]

Thanks!

[@CuriousMarc]

Well thank YOU!

[@fixthetempo7276]

beautiful!

[@ikocheratcr]

It would be nice if you also do some elevator music explanation about the laser diode and the setup you showed.

[@danielatbasementtech]

Fascinating as always ... I love the electro-mechanical solutions of the 60's and 70's. The servo board schematic is remarkably simple for HP ?

[@gwogg8209]

Fantastic episode!

[@BlaMM74]

It's too bad DeOxIt doesn't make ReCapIt spray:)

[@CuriousMarc]

Lol

[@danl6634]

That would be a very spicy can!

[@JoesComputerMuseum]

Hello from KansasFest! Great Job, Marc!!

[@douro20]

How about a Moseley chart recorder? I used to have an amplifier/marker generator for one- all tube based.

[@CuriousMarc]

Yes, a nice Moseley Autograf! You know that deep down the HP 7044 is a Moseley too. HP got an 80% stake in Moseley in 1958 and purchased the rest of it in 1964, becoming the HP San Diego division. Who made this recorder. My older HP 7035 looks straight out of the Moseley catalog. It is said that Moseley invented the X-Y recorder in 1935.

[@dwightelvey645]

@@CuriousMarc I have an original Moseley and the plastic block like his was also broken. I've been meaning to make a new block on my small lath/mill. It is an older amplifiers that used a Novistor tube amp instead of transistors for the input preamp.

[@CuriousMarc]

@@dwightelvey645 Oh, interesting that I am not the only one! Nuvistors are very cool devices.

[@kingofcotham9999]

Hi CuriousMarc Fantastic video as always. Please can you explain the 'dialectric grease' you used. Why did you use it and what is it's applications and where can you purchase it. Thanks Duncan

[@mydogpeaches1]

back when i used to repair computers i used to call the mysterious fixes that you could not figure out was known as the computer car ride phenomenon lol the computer just wanted a day out in the country side

[@johnopalko5223]

In software we called them heisenbugs.

[@user-sy6lc6hv7e]

Thanks Mark!

[@intell2OOO]

"unrepair itself" LOL 🤣🤣🤣

[@InssiAjaton]

I think the LM201 had already fixed the latching problem - or am I wrong? I used to battle that with uA709. . But as far as the HP XY plotters go, I have ‘45 waiting for a miracle find for TWO pens. It is XYY actually. My other XY plotter is a Heathkit that I assembled myself. It also needs refurbishing its pen every time I use it. And soon also cleaning of the rails and feedback elements. A fancy solution it has for the paper hold down is a slight vacuum delivered just fan blades on a low cost motor. If I recall, it uses uA741 for its servos and has a selectable bank of capacitors to provide jitter filtering.

[@jakint0sh]

<a href="#" class="seekto" data-time="258">4:18</a>: **angry servo noises, hitting end stop** "UHM, heh I'm not sure we've made progress."

[@cda32]

You changed the outcome by measuring it

[@Vascinator]

Thanks, Marc. Nice job on the pen transplant. I have a 7035B plotter whereby the platen film has completely separated from its green glued-backer. It is also wrinkled and warped. Any idea how I can replace/repress that film and which glue to use?

[@CuriousMarc]

I would take it off and try to use some Monokote instead.

[@supersonictumbleweed]

Is it a good assesment (from quick googling) that op-amp itself in a loop like this has a response time of 5ns? If so that's mighty fast! Analog computers are terribly underrated.

[@mikefochtman7164]

@<a href="#" class="seekto" data-time="1459">24:19</a>, I'm yelling at the screen, "Not the Op-amp, it's the slidewire wiper!!!' lol I'll watch the rest to see if I'm right, but I bet the wiper is losing contact from the slide. edit: Ha!!! we had a couple of those, it was ALWAYS the slidewire!!!

[@TrueBlue475]

As usual fascinating content Marc, i had to laugh out loud, 7 very grumpy individuals have disliked this Vid at the time i watched, Why? what on earth was there to dislike!

[@chefchaudard3580]

« It un repaired itself! »… yeah… typical service engineer speaking 😂

[@liquidsonly]

That's a tip wicking, pot cleaning, op-amp soldering episode. Nice. All the skills.

[@douro20]

I personally forgot about the problem with latch-up on op amps.

[@benhetland576]

What's the difference between a regular X-Y plotter and a "recorder"?

[@CuriousMarc]

You probably mean what's the difference between a pen plotter and an X-Y recorder. They are cousins of sorts. A pen plotter is a digital drawing device controlled by a computer. Some do move the pens just like an X-Y recorder, others have paper on a drum or moving around in the Y axis. An X-Y recorder is an analog lab instrument with fixed paper that moves the pen in X and Y position from two analog input voltages. In the 1990s, HP had one instance of a hybrid device, which was foremost a digital plotter for a computer, but had an A/D converter input stage, so you could also use it on its own as an X-Y recorder in the lab. I can't remember the number of the machine on top of my head. But it was not as nice to use nor as fast as a pure analog X-Y recorder. Conversely, you could transform an X-Y recorder into a pen plotter by putting a D/A and some digital controls in front of it, and that's how the first pen plotters were actually made. And to confuse things even more, there is yet a third variation, the chart recorder. This one has a constant speed rolling paper going under an X-only moving pen. That's the one you'd use to record EKGs for example. HP San Diego made all three of these, sometimes using related mechanical innards.

[@benhetland576]

@@CuriousMarc Ah, thanks a lot for the good explanation! I didn't even know they existed, but I knew about plotters from back in the days. They used to be the common choice when anything with graphics were to be "printed" from a computer, like technical drawings or diagrams. On the programming side I remember graphical plotter libraries in use long time after plotters became rare, mostly replaced by dot matrix and later ink or laser printers. The same libraries were also used with output to other graphical libraries like monitors and picture files. That HP plotting language became the de-facto standard for a while. So the recorder device is essentially the paper equivalent of an oscilloscope in X-Y mode then :-) I believe the constant X or Y speed devices like the EKG ones also existed with multiple pens so they could "record" multiple channels, but sadly the modern ones have become boring and lost the cool mechanical pen arms now ... but they do add text and other things like annotations to the graphs. I was disappointed that they no longer spew out the paper in real-time, though, the last time I was in for a check.

[@Powertampa]

Don't say it too loud or HP might get the idea that they are entitled to their old manuals or something. Bad enough people try to fleece you for them on ebay, don't need HP to also require a license to like read them or something.

[@milantrcka121]

Keysight (HP/Agilent) website has a repository of old manuals, scanned. Follow "Support". Paper manuals are nice for nostalgic reasons but the scanned ones work almost as well. If need be, specific pages can be printed.

[@antronargaiv3283]

Yes, many thanks for scanning the manual and posting it for the future.

[@Millay2006]

Someone could 3d print the pen cartridge ready to accept sharpie innards... Because JP weld is a one time only fix :)

[@624Dudley]

Delicious. 👍

[@QuintinMassey]

<a href="#" class="seekto" data-time="456">7:36</a> that made me laugh

[@boots_n_coots]

Ok, my Hughes Aircraft cryolab homies- slide a fresh chart on the table and let’s make some cold-displacer hysteresis plots!

[@magomat6756]

You could 3 dprint a new pin 😊

[@yuppiehi]

What duct tape did for the 20th century, JB Weld will take us through the 21st century.

[@68hoffman]

yay! :)

[@davidboettcher1900]

Hi Marc, I remember using a plotter like this in 1975 when I worked in a lab doing simulations of hot gas release from a gas cooled reactor. It had more than one pen as I recall, maybe 5 or 6, do you know that one? I can still remember the pens tracing out multiple different coloured curves at the same time of pressure changes in different parts of the model, a physical scale model of the plant, Hartlepool/Heysham 1. (Funny thing, after nearly 50 years, I have only just realised that Hartlepool doesn't have a 'y' in it, even though it is pronounced as if it does: Hartley-pool.)

[@CuriousMarc]

There is the HP 7046 that resembles this one, but it has only two pens.

[@davidboettcher1900]

@@CuriousMarc I might have been a couple of years out with my date of 1975 and the number of pens. It might have been 1977, and perhaps it was an HP 9872. vtda.org/pubs/HP_Journal/HP_Journal_1977-09.pdf

[@CuriousMarc]

Ah yes, that would be a digital plotter, not an analog XY recorder. A cousin/nephew of sorts. Famous for having so many pens.

[@Putersdcat]

schrodinger's gremlin 🎉

[@philmayf]

Is that a Kuru Torga?

[@iamdarkyoshi]

Lasers!