HP 7035B X-Y Recorder Restoration Part 2: Back to its Former Glory.

[@johnopalko5223]

You're contagious. I've been finding myself referring to random things as "doodly-doos."

[@absurdengineering]

Hopefully random websites :) www: look closely :)

[@metasequoia12]

You are a patient genius! It is a true pleasure watching your videos. Thank You!

[@scowell]

I found this same problem with CdS response when working with guitar amplifiers... Fender used a 'roach' (neon with CdS heat-shrinked together) for their later tremolo circuit. If you try and sub a generic CdS you find that it won't work well... CdS cells are slow to respond, so Fender had to find special ones that work fast enough for the tremolo effect to sound good.

[@justovision]

I've never heard it called a "roach". The term vactrol is pretty common for synths and amps. I've never heard of anyone needing a special LDR for one though. They max out at 10-20hz? Fender never used special anything unless it was special because it was cheap :)

[@jlwilliams]

Wow, last week we were doing a clutch job, and this week we're dealing with gear backlash. Welcome to Curious Marc's Garage!

[@LikeDotAudio]

Thank you for this act of preservation

[@TechGorilla1987]

I certainly didn't expect to get a resolution so soon!

[@landspide]

very punny!

[@DrFrank-xj9bc]

About 33years ago, I repaired a lot of hp7004B plotters, those with the small amplifier / time modules.. very fine instruments. Once I got nearly electrocuted, due to a scratch in the lacquer of the HV paper hold-down. 😜 The experiments on High-Tc-Superconductors went over many hours, so finally leaving a big ink blob on the paper.. In turn I could finally convince my prof. to let me develop DAQ via GPIB - DMMs (bad Keithley 195A) and Borland Pascal on PCs. The PDP 11 had just been scrapped. Those were the days.. 😍 For the FLUKE 845AR optical chopper we found modern neon bulbs from Barthelme, type 82305, which show no dark effect. Maybe that's a hint to replace neons in HP devices (e.g, hp419A) as well.

[@SuburbanDon]

This brings back 40 year old memories for me.

[@AttemptingAstro]

In my CNC with the pen holder on, I'm a big fan of pigma micron pens. Seems to work on multiple paper types, can adjust line thickness given that the pens come in different thicknesses. The 005 is super fine, but I usually use an 03. The felt tip also has just enough play to keep it smoothly on the paper.

[@Zardwark]

I'm relatively new to this channel, but one thing I have learnt... I am not worthy to kiss the ground that Marc has walked upon!

[@zh84]

I'm glad the deluxe breadboard with incorporated test equipment is being used the way it should again.

[@KeritechElectronics]

So nice to see you use the electronics prototyping kit for testing this plotter - vintage gear restored and loved. BTW reverse-engineer the D-sub connector next to the mains connector, if it's not documented. Cool timebase module too. A good demonstration of how an oscillograph works. Loving the ASMR mode!

[@theelmonk]

And the 3312A function generator too

[@rallymax2]

HP logo. ASMR. Heaven.

[@glennbruner7504]

Master Ken and his subtle words of wisdom. Pulled you out of photo-resistor sourcing hell! Good job!

[@simonturnill]

Just a casual spare Jaeger Le Coultre box lying around (as you do). Disappointed it wasn’t an A Lange & Söhne… 😉

[@mskurnik]

Please post a 15+ min ASMR video of the plotter going.

[@1971merlin]

Live stream. Plot the space shuttle.

[@jasonchua7283]

Short wait!

[@tezinho81]

(almost) Instant gratification! Merci m'sieur!

[@8BitNaptime]

Flatbed pen plotters are so elegant, I want one now.

[@djmips]

...you might remember Part 1... from 3 hours ago! (They seem to be originally posted 3 hours apart hehe)

[@adamthekiwione]

The quiet flex of using a JLC box ;) lol

[@thebiggerbyte5991]

Hewletch-a-Sketch, surely? ;) I love seeing this beautifully engineered old equipment in action, so I am looking forward to the next episode.

[@MeriaDuck]

15:12 that's quite an expensive etch a sketch! And congrats with the result (both technical and your drawing, I would've made a mess just like 40 years ago)

[@jurjenbos228]

Maybe you can put a double a-d converter in it so you can save your drawings

[@largepimping]

Two videos in the same day... **and** ASMR? This is too much...

[@yurymerezhuk7031]

Nice and encouraging! Not to mention that light blocking cap looks very similar to the film container :)

[@iNerdier]

And cadmium sulphide cells were used for early automatic camera light meters! It’s got me excited we might see some vintage camera repairs, maybe, please?!

[@leon545b]

I have a 9872a plotter in need of restoration, and I bet it shares some of the mechanical characteristics of this guy, so, this video may come in handy. Thanks Marc, good work as usual!

[@thcoura]

5:24 Through the magic of video edition.

[@svenax]

A Jaeger-LeCoultre box for the etch-a-sketch controller - was that something you just had lying around in the lab? 🙂

[@CuriousMarc]

Yes I collect watch boxes (they look nice but they are very crappy plastic or wood underneath!) for projects. My Nixie clock, my TI LED clock, my Thermoelectric-inator are all dressed up in watch boxes.

[@gregkrekelberg4632]

@@CuriousMarc Do have one of these watches? They're gorgeous.

[@CuriousMarc]

I do! They are!

[@izzieb]

That's a nice Etcha a Sketch you have there.

[@ahge1]

Very interesting! I didn't know about photochopper! A very creative solution!

[@Consequator]

So, for next weeks video we're expecting you to draw an apollo rocket with the hewletasketch, obviously.

[@tim_bbq1008]

That's a high tech spirograph. Thanks for sharing!

[@Electronics-Rocks]

WOW MIND BLOWN!! I thought those tubes was some form of isolation! I repaired one over 30 years ago but it was the power supply. Interesting using cadmium sulphide as I did not think they would react fast enough but it is only 60hz. Sad but lost all my HP service manuals due to a leak flooding the box stores them. I see you with the HP book where I feel my loss.

[@Broken_Yugo]

Similar arrangements were used for high voltage optocouplers. Might still be in some cases.

[@alexdehotot2712]

Now i'm really interested in how it un-chops!

[@edwinschuddemat8280]

We should start a petition.

[@yorgle]

The photochopper is such an amazingly simple and unique solution to the problem. I love it. Have you looked into Motorola's vibrasender/vibrasponders? They're a neat bit of lost technology too..

[@agranero6]

Wow...my father worked with some Motorola police/firefighters radios that used vibrasender/vibrasponders to allow several groups share the same frequency, but activating only the selected ones when sending a call.

[@yorgle]

@@agranero6 It's amazing that it worked in the analog days, and it's such a simple concept at its core...

[@miked4377]

great job marc

[@oldguy9051]

Hewlett-A-Sketch -> LOL! What's next? "Hewlett the dogs out?"

[@motionsick]

Haha this is so awesome. Love the channel man. Thanks for sharing.

[@EngineeringVignettes]

I guess a backup plan would be to just make a skinny PCB and hide it in the tube... use a fast photocoupler on it. If the original parts are made out of unobtanium. Nice plotter :) Cheers,

[@ollyshighlightreel6530]

I am not sure that this has been asked already... Marc, could you please make a ASMR video of the plotter please? Those last 10 seconds was incredibly relaxing. Please and Thank You in advance.

[@estyrer2]

It had a Zappa ‘Joe’s Garage’ feel to it as well. 😊

[@richardkelsch3640]

Due to excess vibration, Marc had to put his tool in the slot... (Beavis & Butthead giggling)

[@HeyBirt]

Perhaps you could build a replacement sensor around a modern photodetector? A CDS cell typically has a response time in the tens of ms, a quick search turned up a VTPS1192HB-TR which has a response time in uS. No doubt you will need some conditioning circuitry too.

[@thesushifiend]

Careful with ordering components. They might send you ceramic beads and you might eventually end up with all the parts to build an interociter. And we all know what happens after that!!

[@KarlAdamsAudio]

It seemed so promising - "Laying a four-lane highway at the rate of a mile a minute would be a cinch!", then you rotate the intensifier disk 18 degrees counter-clockwise, and it's all downhill from there...

[@Droisntns]

So hew let the scetch out?

[@Mrshoujo]

Now you just need computer control and have it draw a side view of the Starship Enterprise like they did at a local technical college for Open House nights.

[@MrCydoo]

Bravo Marc, à la fin tu as reinventer le télécran ! ^^

[@williamsquires3070]

Well, you almost gave the makings of a CNC router, there. You just need a X-channel amp/motor driver, the motor, and the Z-axis hardware. Then attach a spindle motor, or a 3D print-head, and a place for the 3D filament. Ta-daa! I think Mr. Fancy Pants would be proud.

[@TheLaurentDupuis]

We need a 8 hours ASMR trace of some nice signal.

[@ToTheGAMES]

No we don't

[@dr_kav2k]

ASMarc

[@Evergreen64]

I noticed that the box you used for your HP a sketch controller was a Jaeger-LeCoultre watch box.

[@monomo108]

Block the half of the new to sensitive photoresistor. To finetune the sensivity.

[@FF177-]

Its not too sensitive its too slow

[@benjaminhanke79]

00:10 is when I realise I slept through one whole CuriousMarc video.

[@garynichols1502]

Would love to see you use it with the HP8903!!

[@guygadbois1068]

god i wish i had a friend like you to help me fix my 3 dead reverse cycle split system air conditioner PCB's

[@mikek5633]

Ca fonctionne tres bien maintenant!!!

[@HfLuo]

This is a nice piece of instrument, which I'm still trying to get one. I'm surprised to see that the mechanical parts, resistive position sensors and even the electrostatic paper holder are almost exactly the same as my HP 9125A plotter for the HP 9100 calculator. However in the 9125A plotter, there's no photo-chopper anymore. They used integrated opamps to do the feedback control. Digital x-y coordinates are converted to analog and fed into the control loop to drive the two axis. I have a complete teardown of the HP 9125A plotter on my blog but I don't know if its OK to put the link here.

[@CuriousMarc]

sure put the link in a response comment and I’ll let it through when it comes up for review.

[@jb5631]

Can you still post the link?

[@HfLuo]

@@jb5631 I tried but seems it didn't pass youtube. I'll try again below to see if it works.

[@HfLuo]

Teardown of the HP 9125A plotter: 7400.me/2021/05/05/HP9125A/

[@QuasarRedshift]

I think that something like this was in one of the opening scenes of "The Andromeda Strain" - so long ago . . .

[@ludmilascoles1195]

Lools like HP reinvented the Ociliograph

[@Richardincancale]

I remember these from 40+ years ago! Can you explain how the paper hold-down function works - could never figure that!

[@Snape1337]

Can we get a 10 hour video of the HP 7035B X-Y Recorder making curves?

[@X5Industries]

Is that 25-pin remote cable you used for your etch-a-sketch box an original TTL remote cable or did you make it yourself? I’m wanting to use mine with my 85XX/141T Spectrum analyzer and I’m missing that specialized cable (I’m not even sure what it looks like…they seem to be unobtanium online). I find it mildly frustrating that HP never released a model that featured a top-side accessible Pen Lift port using either banana jacks or BNC

[@CuriousMarc]

It’s one I made. Just looked up what the pinout was in the schematics - somehow it wasn’t documented anywhere I could find. But it’s simply X, Y and a switch to ground for pen lift. I also added a protected power pin so I could power my pots.

[@X5Industries]

@@CuriousMarc Thanks so much!!! Do you happen to remember where you purchased that connector? Looks very compact compared to the traditional D-sub housings

[@CuriousMarc]

@@X5Industries Standard Amphenol connector, same as HP-IB. Widely available. I had one in my box of goodies.

[@NinerFourWhiskey]

Cheat a little and use phototransistors or even opto-isolators with a little circuit modding?

[@discow00t]

Brilliant and funny as always :-)

[@Hilde_von_Derp]

Not gonna lie, but, yes I would just watch a few hours of this peacefully plotting lissajous.

[@handmadepro3137]

hello! You are watched in Ukraine. Your KZbin channel is an incredibly high technical level. About this analog plotter, almost everything is clear, except for one nuance. How is the feedback on the actual position of the carriages in X and Y?

[@T3sl4]

See previous episode -- there's a wirewound resistance track along each axis, with a sliding contact. Very old fashioned, no encoders to be found!

[@letsgocamping88]

like an RC servo.

[@absalomdraconis]

... 0:34 I just realized... _they used fuse holders to hold those light-blocking tubes!_ You can just buy those things off Ebay!

[@thcoura]

Jesus, 7:26 that cap was those we used to protect the film roll to photo development?

[@mcarey4725]

Where did you buy the repair components? I am always looking for sources. Thanks.

[@CuriousMarc]

All the components in this episode came from mouser.com. But for the CdS cell, I got lucky that a viewer that saw this episode gave me some prototypes he had kept straight from his time at the HP labs in Palo Alto. I found one that was identical, replaced it and that fixed the amplifier!

[@agranero6]

Like I said in the other video: LDRs are very, but very slow in the scale of almost a second. The ones used on this plotter must be some special type ones.

[@boris3320]

actually you're not *that* bad at etch-a-sketch !

[@landspide]

Can you block off a portion of the photo sensor (aperture) to reduce sensitivity?

[@zyeborm]

it's too slow is the issue

[@teslakovalaborator]

That silver photoresistor looks like an old Tesla brand WK65065 to me :D

[@leon545b]

Does anyone know when the first and last HP catalog dates where this was offered?

[@alexscarbro796]

Is the output switch in the circuit diagram the correct way around? It looks like it’s switching the opamp output to ground?

[@mymessylab]

I believe I’m facing the same problem with photoresistor in my HP 741 differential voltmeter. Beautiful machine but… shhh… ASMR mode

[@Ajinkya_Mahajan]

How does the unchopping in the plotter works ??

[@danmenes3143]

What happens if you boost the current in the neon lamp to 125 mA?

[@absurdengineering]

I wonder if a non-optical current switching chopper could work for this application. Nothing to do for me but get some old transistors and experiment!

[@pete3897]

I wonder if a suitable high speed signal could have been crafted out of that sensitive photo conductor by placing a light blocking object between it and the LED, eg a piece of black paper, with a small hole in it?

[@thcoura]

Sorry for the off topic question: Aging is a natural effect in semiconductors as the dissipation of dopants, for instance, will progress even in room temperature resulting in changes of electrical properties of component. My question is: How on space missions they handle this? Just wondering.

[@blenderbuch]

Hp a sketch was filmed before fixing the wiggle 🤣👋😊

[@devrim-oguz]

What if you replaced the photochopper with a modern chopper amplifier? Would it work even better? (Although losing its cool)

[@jxh02]

Why are the chopper tubes so long?

[@proton6731]

Well that was fast haha

[@5mf1nc]

0:48 it may be a nitpick, but shouldn't the lower photo-resistor connected to the opamp (+) input instead of the "input" of the other photo-resistor?

[@teslakovalaborator]

Yes, also it is simplified a bit, the 7035B itself uses differential method to null out both inputs, see the schematic.

[@GodOfMetal1991]

if you need an idea for a giveway to your patreons or someone, print a nice wave like the one in the end and sign it. if i had one i woud frame it and hang it on my wall :D

[@jadney]

Could you replace the CdS with a photo transistor? Or would that be cheating?

[@francescozani9488]

Oh, my. I used this for actual job. Am I THAT old?

[@kernealalpiniste6293]

My plotter don’t jiggle jiggle…

[@winged_neko]

probably the gear made from plastic expanded a bit over time and so the clearance got too tight.

[@CuriousMarc]

I was thinking just the same!

[@csudsuindustries]

ASMR hp Girlfriend plots after a hard day at work. Genius

[@1971merlin]

Beats ascii line printer art I suppose.

[@JohnRineyIII]

I’m sorry, Digikey has radioactive neons from the 60s in stock?!

[@Broken_Yugo]

I pulled the datasheet and didn't see anything about radioactive properties. Probably just the same size and electrical specs.

[@erikdenhouter]

An oscillograph....

[@maicod]

shhhhhhhhh :)