Bendix Air Data Computer - Part 4: Magnetic Amplifier Magic

Thermal Camera TC001(android): www.amazon.com/gp/product/B0B... (Apply $20 coupon with Prime: $229)
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We power up our analog computer for the first time, and are stumped by evil magnetic amplifiers.
Bendix MG-1 Restoration Playlist: • Bendix Central Air Dat...
See Ken’s full explanation of the inner workings of this computer in his blog article: www.righto.com/2023/02/bendix-...
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[@rvoisey]

The main problem with thermal cameras, as demonstrated, is that every job takes twice as long. It's impossible to resist looking around your workshop and playing with it!

[@CuriousMarc]

It’s like, it gives you super powers.

[@olik136]

the number of wall plug transformers I found randomly hidden around the house.. and other current drawing devices that sat there for years without using them..

[@gamerpaddy]

problem 2: you never have it around when you need it

[@benjaminhanke79]

​@@gamerpaddyThis! Some years ago I bought a CAT mobile phone with integrated FLIR™ Cam. As I use a new phone now the old one is always at home.

[@bennylloyd-willner9667]

​@@gamerpaddyI have one in my phone so no worries for me😊

[@oetken007]

Emissivity is an important factor when you are working with the thermal camera. Shiny objects like metal does have a very low emissivity and reflects infrared radiation very well. You think you are measuring an object, but in reality you are measuring yourself, reflected by the object. A simple way to solve that issue is, to stick black electric tape on it. In some cases it is necessary to paint the object. It is quite complicated to get usable "measurements" from an infrared camera. Have fun! 😎

[@gertebert]

It's 9 Am in the Netherlands. Just arrived at work. Turned on the PC. See there is a new CuriousMarc vid. The thought of watching a new vid at home in 9 hours will drag me trough the day.

[@gertebert]

Update: it was worth to wait :)

[@ragrabau]

Many years ago, when I was in the Navy (1970), and they tried to teach me about magnetic amplifiers. Marc, you taught me about magnetic amplifiers. Now I understand. Thank you Sir. Also bought a thermal camera for my phone.

[@Hunter271828]

Love this video! I bought a 1.5kW-28VDC Military Generator built in the 1960s and it has a small potted voltage regulator that uses a magnetic amplifier too. This device monitors the output voltage of the generator, and controls the field current to maintain a 28V DC output. It uses no transistors, and is still working after all these years. I was surprised as an EE when I came across this magnetic amplifier because it was something I had never heard of! An amplifier that doesn't use tubes or transistors!? Crazy!

[@gregorymalchuk272]

I always wondered how small generators regulated voltage prior to transistorized voltage regulators! Do you happen to have the name and model of the generator? I would love to learn more about it.

[@Hunter271828]

Google "MEP-025A manual" and you should find the manual with schematic

[@thesteelrodent1796]

always amazing that Ken so easily can figure out something so incredibly complicated. That machine truly is a marvel of engineering and it'll definitely be fun when you start building a plane for it to go in ;)

[@Damien.D]

Master Ken is a marvel of engineering by himself :P

[@zyeborm]

Well they need to build the chase plane for the Apollo rocket they are building right?

[@alexpinkerton7459]

Excellent as ever - and many thanks for the explanation of "Mag Amps" - a technology that I never knew existed! How did my college lecturers miss that one?

[@lwilton]

I recall my dad making magamp-based regulated DC power supplies for satellite use back in the 1960s. I learned a lot about transformer and inductor design from him, but I haven't had to use that knowledge in 60 years or so, and it has all dribbled out of my head. I also seem to recall that tantalum caps tended to work like zeners if you weren't careful and even slightly exceeded their breakdown voltage, and the breakdown voltage could degrade over time.

[@mikefochtman7164]

Back years ago (~70's), when I was in the US Navy, we used MagAmps quite a bit for instruments and such. There were two categories as I remember, a 'saturable reactor' type, and 'self-saturating'. Many transducer's we had were variable-core transformers so using magamps to amplify and then driver servos was a common arrangement. But we started getting newer stuff with solid-state. So I when I was in, you had to know both, depending on what equipment your ship had.

[@petesapwell]

Recently came across a magnetic amplifier in an colour CRT Arcade monitor, it looked very similar, a pincushion transformer where the signal from the vertical output stage is used to control the width. Fascinating :)

[@sandheaver44]

That transistor is a Transitron ST905, and is an early silicon transistor. It was Transitron's version of the Texas Instruments type 905 silicon transistor.

[@marvintpandroid2213]

Bendix, we are not just into washing machines

[@EdwinSteiner]

For more Bendix, you can check out Usagi Electric's vacuum tube computer. It has a magnetic drum memory reminiscent of a washing machine, though.

[@lwilton]

@@EdwinSteiner More like a spin dryer. 🙂

[@tocsa120ls]

Time to hook up a temp sensor to it and build possibly the most complicated weather station 😄

[@CuriousMarc]

That’s a great idea. We’d get the temperature from the platinum probe, the barometric pressure from the static port, and if I could build a rotating pitot tube that always faced the wind, I could get the wind speed. Imagine, I could measure wind bursts up to mach 2! That would put these storm chasers to shame…

[@RingingResonance]

@@CuriousMarc My uncle had the pieces to one of these and we used to play with the differential gear sets when we were kids. He told me about how syncros work and how at one point he used a pair to work as a wind-vane. One syncro on the roof with an actual wind-vane attached to it, and the other inside with a pointer on it. He said it worked really well until the wind blew it off the roof one day. Maybe you could so something similar to control the rotating pitot tube.

[@petrusbosman4264]

I have been using my Cat S62 Plus phone with Flir for many fault finding and diagnosis in electronics as well as picking up gas leaks on anaesthesia workstations.

[@Runco990]

The first thing I did with my new thermal camera is take pictures of my black cat! It was quite interesting, actually! On topic, it is just amazing to marvel at the electro-mechanical solutions of the time. Just amazing..... And to think of the weight restrictions they had to overcome in an airplane.... all that with paper and slide rules before we had computer assisted design.

[@siberx4]

I had never heard of magnetic amplifiers before but as soon as you mentioned applying a DC bias to one my first thought was something to do with saturation; what interesting devices!

[@octane613]

Ive watched all the vids on this and the apollo modules. Between those series, you guys are insanely talented and intelligent. These computers look far beyond my technical capabilities.

[@absurdengineering]

Not only are fingers not sensitive enough, but they confound the results. They are so comparatively warm that it’s easy to heat things up inadvertently just by touching them. Especially in a well air-conditioned basement. After all, a finger tip is a miniature heat exchanger. Fed with warm blood, all those capillaries do an amazing job of dumping heat. With a bit more sensitive camera you can see hot finger “prints” left on things just by touching them.

[@michaelmiller641]

Absolutely amazing machine! Ilove watching that gearing moving!

[@generaleric567]

never been so fast on a new curious marc video

[@sweetpeaz61]

Master Ken once again proves he truly is a master.

[@KieranOCarroll]

Fascinating to watch - and time travel back to an earlier avionic era. Thank you for the reminder of how mag amps work!

[@hymermobiler]

Another 20 fascinating minutes glued to the screen watching very talented people at play 🙂

[@scowell]

Master Ken's abilities are amazing! Both knowledge and patience without bound. I recognize that decade box... my first ham receiver was a National. A real vintage piece. Want that Topdon TC-002 now! 240$ for IOS.

[@mikafoxx2717]

So now we've got two KZbinrs working on Bendix computers? What a time to be alive!

[@Drew-Dastardly]

This one is a specialized analogue flight computer. Usagi's is a digital general purpose computer.

[@mikafoxx2717]

@@Drew-Dastardly yeah, I know, but they're both equally cool old computing devices

[@islandhopperstuart]

Learning from every episode: thanks guys!

[@mixolydian2010]

Thanks guys it's a thing of beauty.

[@malcolmgibson6288]

Coffee, crumpets, and Curious Marc. It's a great way to start the day.

[@LesNewell]

Mag amps are very versatile, from tiny little ones like this to ones that can handle 100s of amps in welders.

[@parkerlreed]

Part 3 Part 2? :) Can't have enough part 3's.

[@alexscarbro796]

I’m sure you will find the thermal camera as a very useful PCB fault finding tool, as I have.

[@tekvax01]

So very interesting! I have been a fan of synchros and resolvers since the mid eighty, when I was introduced to a telecine film chain, that used magnetic film stock with the optical film, and the entire thing was locked together. my next introduction to them was with an old teleprompter table that locked the motion of the hand controller with four separate motors that dragged the paper down the table, whilst the camera photographed the words on the pages and displayed them in the prompter CRT on the camera peds!

[@swebigmac100]

Amazing piece of kit actually. Would be awesome to find the geniouses designing it

[@VegasCyclingFreak]

I've never even heard of a magnetic amplifier. Interesting stuff!

[@ptonpc]

Another great video of a fascinating device. Thanks :)

[@T3hBeowulf]

This, like many other series, is absolutely fascinating. It really brings context to the stories my Grandpa used to tell about his long career working for Bendix in their test division. Thank you for sharing these amazing adventures with us! 😊

[@grubboy3514]

Master Ken at his usual best work!

[@TheGunnarRoxen]

Ken is a very smart guy. You are all very smart folks. It is a delight watching you figure out these machines.

[@tocsa120ls]

And it's a relief to know he has a heat signature 😂

[@peteroneill404]

I recently bought a different brand of IR camera for my phone and love it. To make it easier to use I bought a cheap pistol grip for my phone to have single handed operation.

[@unmanaged]

Marc great as always....

[@junglemike4]

Excellent. Thanks.

[@38911bytefree]

This air computer is a magnificent piece !!!!!!

[@cambridgemart2075]

I've encountered the saturatable reactor 'mag amp' in the power supply of a shipboard communications system. The 3 phase AC was fed into it and a DC current controlled the output. The previous systems had used a motor driven variac to do the same thing.

[@SteelHorseRider74]

quite interesting to see such mil-spec tech from 50s and 60s; never knew about such magamps before; thanks for showing! I think the moon landing also accelerated the move from rotating gears towards silicon-based calculations (and everything done in software) in the avionics industry. Imagine an Apollo Guidance computer with such rotating gears, instead - if such jump in tech would not have happened in the 60s!

[@paulcohen1555]

I have an tantalum capacitor of the same style made in the 60's and it's still PERFECT!

[@MarcelHuguenin]

Another great wizardry episode by Master Ken and 'ThermalCam' Marc . How on earth could you guess my question about the magamp? 🤣 People were quite inventive at the time. Also the reverse engineering skills of Master Ken are on another level, amazing work. Thanks for the video Marc.

[@gabotron94]

5:56 got a bunch of these from a "mystery parts box" and always assumed they were inductors!

[@CuriousMarc]

You wouldn't have one that's around 50 Ohms by any chance?

[@chemputer]

Cheap thermal cameras like that have been available for less than $300 since the early 2010s, Flir One Gen 1 was the first "big" one. The resolution of the thermal imager is low, only 80*60, but they compensate for that by combining it with a normal camera to get the fine detail and use the thermal camera for the thermal information. For the resolution it's surprisingly sensitive. I still use it today, it's got a micro USB on it but if you add a micro USB to USB-C adapter, then it works perfectly fine!

[@proehm]

We had a piece of equipment (30 years ago) that had hundreds of those caps in it, and ended up replacing them all. Fortunately they were mostly on memory cards for the video processor. That allowed us to pull the D0 card to repair while leaving the D1 - D7 cards in place. (All cards were identical.)

[@Matt47247523457]

"The finger of blame" - I like it

[@davidbrowne1588]

Great videos as always, Funny enough I have the topdon tc001 coming today, I have been looking in to fitting a macro lens, I have found a lot of info on the eevblog, I will order a lens later today, I just need to find some one with a 3d printer, Thanks Dave

[@624Dudley]

Super interesting, guys! 👍

[@vincei4252]

That Fluke 101 is super cute. I think I'll get one just because!

[@rogfusionkid]

Great videos, a lot of it is beyond my understanding but it's so interesting. Hey you guys have so much to offer, I hope you inspire more people to learn and be clever.! That's got to be a good thing. I wish I could do these things, fortunately you guys are doing it instead.

[@jameshackett9992]

Magamps so old but so new i am now going to experiment with these, I've have spent ages on books just on making transformers a dark art like microwave circuits

[@Allan_aka_RocKITEman]

@CuriousMarc >>> Something just occurred to me while watching this video. This may have already been said before, but even if you guys could not power up this thing and test it, just having it on display with the outer casing removed would be a cool piece of 'aviation art'. Put it in a glass or plastic cylinder fitst, just to protect all the 'innerds' and keep them dust-free.

[@ronjohnson9690]

Fascinating stuff. My subconscious mind must be grasping 90 per cent of this while my conscious mind understands 40-50. Otherwise I would not be so captivated by it all. My faith says at some point a connection will occur, and I will light up like a Christmas Tree!

[@jensschroder8214]

Whenever it gets scientific we use °Celsius. When it comes to how an American feels, we use Fahrenheit. When an American sweats, it has to be 100°F. And when an American is cold, it's 0°F

[@JoseHernandez-md8tv]

Love your series and this particular one. Please, please ask Master Ken to do an introductionary video about reverse engeneering. I would especialy like to know how he gets from then net mesh you showed on paper into a schematic drawing. What tool is he using for that and which techniques are involved?

[@DouglasFish]

I bought the same TOPDON camera. I love it way more than I thought I would. It's fun to follow around footsteps or see what animal was playing in the water dish/cold footprints

[@neiljolliff8170]

I use mine for finding my dog's poo in the dark😂

[@jeffreylunger]

I want Ken to introduce himself at least once by annoucing "Hey, it's ya boy Ken up in the house!"

[@98xjdriver]

I have the topdon tc005 dual imaging thermal camera. It's a cool tool. Easily worth the modest amount of $$$.

[@Rob2]

But did you already install the Bendix app to control and monitor the Air Data Computer?

[@A2CVMAN]

Just brilliant:)

[@explorer914]

Can the Bendix computer check if I'm first?

[@CuriousMarc]

Definitely! Google says you are second, but they use crude digital techniques. The Bendix, on the other hand, uses subtle and refined analog estimations, so it says that you maybe first more or less approximately perhaps close enough.

[@SteelHorseRider74]

sure, but the Bendix might have to shift into an extra gear for this 😂

[@explorer914]

@@CuriousMarc Well to be honest I do think digital readouts are a little crude, if it don't have lots of decimal places of course. As a happy hobbyist I prefer an analog panel mounted gauge. 😁

[@johnopalko5223]

My first exposure to the term "magnetic amplifier" was 30 or 40 years ago when I happened to be reading the technical documentation for an electric chair. It used a saturable reactor to limit the current applied to the (euphemism alert) "load" to 5 amperes at 2000 volts. Ever since then, the term "magnetic amplifier" has seemed just a little bit creepy.

[@Drew-Dastardly]

I believe microwave oven transformers are similarly rated. Another guaranteed death device in the wrong hands (I see you fractal wood burners!)

[@Soren_Marodoren]

Yes, IR cameras are really nice to have when fault finding. But one important part is to not touch the parts that you want to look at. Your fingers leaves hot spots that can stay for some time and fool you. It is also good to have some PVC electric tape and place on metal parts to reduce reflections and give a better emissivity. This will give you a more precise temperature reading and enable you to compare them with each other.

[@StringerNews1]

Eli the ice man strikes again.

[@CliveBagley]

Superb 👍🏼👍🏼

[@denisohbrien]

I notice you use those inline wago clones for test setups too, they really are superb for reliable semi-permanent connections.

[@Allan_aka_RocKITEman]

At 05:25 in this video: FWIW: My previous {'deactivated'} smartphone is a CAT S60, which has a built-in thermal camera. I have taken a few selfies with it, and doing so while wearing my prescription glasses REALLY looks odd...😊 {Thermal IR cameras cannot 'see' through glass.}

[@SeanBZA]

Those tants have leaked, and the heat from desoldering them was enough to evaporate the sulphuric acid electrolyte across the seal that was shorting them. If they have the epoxy seal there is rubber under it, and they fail with time, as they are the "budget" renge of wet slug tantalums. the glass seal ones almost never fail, tested a batch of 500 that had been sitting in storage since the early 1970's, and none were out of tolerance at all, and reforming them did no change at all to the readings for capacitance, ESR and leakage, which was either 1M or higher, or so close to zero it was unmeasurable. Abused a couple on a SMPS to replace the original capacitors that failed, as I wanted it working, and, despite being only 10uF as opposed to the 1000uF they had there, they worked well, just put 6 in parallel on the same pins, and a 470uF after the filter inductor, and got it working again. They ran cool, unlike the old one, despite having a fraction of the capacitance.

[@SubTroppo]

I had to laugh when Ken's reverse engineering diagram appeared; not at his abilities, but my own inability.

[@neddreadmaynard]

Ken. Awesome.

[@RobSchofield]

That was excellent! So when are you going to try getting hold of an Apollo S-V Instrument Unit air data computer module?

[@brucealport8009]

Always a treat to watch and learn. Love the huge Apollo control panel wall poster. Is the image available online?

[@CuriousMarc]

Yes, I got it from here: lunareplicas.com/collections/posters/products/apollo-command-module-banner

[@brucealport8009]

Thnks @@CuriousMarc, that's quite impressive. They're out of stock right now.

[@Allan_aka_RocKITEman]

_"The HEAT is ON..."_ -- Glenn Frey 😉

[@YassineKAOUANE]

Nice servoing indeed

[@jamesbrewer3020]

amazing

[@sloth0jr]

I'd be interested to know what the default failure behaviors on this are, since it seems like a malfunction in flight would be ... bad.

[@poprawa]

-How to compensate for nonlinearity? -Someone will come with screwdriver and calibrate it -Like with potentiometer? That's not possible at all, maybe 20 of them and switching circuit -You know what? 20 of threads that make out a cam will do and don't be a jerk

[@Bublerkin]

Did you manage to restore your HP 7925? I can't wait to see and HEAR it in action.

[@StatusFIX]

Agent smith @15.48 we meet again.

[@EdwinSteiner]

Master Ken rules!

[@davidbrowne1588]

Hi I think that is how old cars like the old mini, and so on, bused to do the voltage reg Dave

[@wirdy1]

As an ex-Nav instruments tech, whose training aids were 1960's analogue flight control computers & air data computers, this content is pure catnip to me.

[@steveschulte8696]

Magnetic Amplifiers, or Saturable Core Reactors, are truely magical. They can be incorporated into linear amplifiers, Oscillators, and bistable Multivibrators with additional windings, i.e. feedback windings. In this application, they are being used in place of high voltage transistors, which in the 50's and 60's are far in the future. Did they use a Platinum RTD or a Thermistor?

[@kevinmerrell9952]

Amazing how this is now done with components you can barely see.

[@twotone3070]

I love spending time with people smarter than me.

[@bfrost999]

What I don’t understand, and I can’t find any reference to this in the description of magamps , is how a control loop is stabilised with such an abrupt magamp change from its BH curve?.

[@NnO0Worries]

'Your're ruining my simple explanation there', 'O, sorry' 🙂 (@ 20:29)

[@vincei4252]

Is the silent ghostly heat signature with dark glasses that doesn't speak Tube Time ? :)

[@dynomatic5099]

mag amps are just saturable reactors. they use them a lot in old p&h cranes in static stepless control systems.

[@bigsarge2085]

Cool.

[@gertebert]

Be very carefull with mister Ken. There is only one out there! I'm sure!!

[@DAVIDGREGORYKERR]

I suspect that things have moved on and they are using many boxes that are behind the cockpit dash.

[@checksum00]

58secs ago, never been that early anywhere

[@intell2OOO]

issue with capasitors look more like tin whiskers problem

[@MrSpathiphyllum]

Great, now you can tell who is a reptilian within your crew 🤣

[@SelinicaHarbinger]

So... the mag amp is kind of like a saturable reactor? if I'm understanding it right