EEVblog 1442 - DON'T DO THIS! (PCB Vibration Testing) 

When I was developing aircraft instruments, we used two shake tables. One was inside a temperature/humidity environmental chamber, and the other was at the center of a 3m magnetic field cube. The one in the environmental chamber was dual axis (XY), and the other was single axis (Z). We had separate operational vibration profiles we had to put the instruments through to meet environmental specifications for propeller aircraft, jets and helicopters. Doing a full vibe test run would take nearly a week, assuming everything went well. We learned so much stuff on the shake tables. We used to pot our instruments, until a shake table test showed the potted instrument actually suffered damage easier than the unpotted one. So we went with only conformal coating instead. We also found that sheet metal changes from switching suppliers could greatly affect instrument resonances, despite the metal stock from each source meeting the same specifications. Which was fixed by pressing ribs into key areas, meaning we could use a wider variety of sheet stock. We used ultracaps for temporary backup power in some instruments. All of which failed vibe testing. We tested every ultracap Digikey carried. We had to get some made with custom mechanical changes (Maxwell was local to us), then support them in a metal cage that tailored the vibe spectrum the ultracaps encountered. That project alone occupied our shake tables for two months. Most shake tables can't deliver high amplitude impulses. When I was developing a super-rugged ultra-high-speed digital video camera we cared more about high level impulse response than vibrational modes. So we got to go a bit caveman: We mounted the camera to a large steel plate, attached a 3-axis reference accelerometer to it, then whacked the back of the plate with a sledgehammer, repeated with the camera mounted in 26 different orientations (6 faces, 12 edges, 8 corners). The camera was used inside cars during crash tests, and within 10 meters of missile warhead tests. It was rated for a lifetime of 100g impacts.

Watching this channel for like 8 years now and hearing Dave complain about to220 "flapping around in the breeze" countless amount of times and now finally he has proven it, we're now fulfilled and can die in peace...

Oh, I gotta get me one of those!

A strobe light is a key accessory to vibe testing. I built a circuit to drive the strobe at a fixed offset frequency from the vibe drive frequency so the unit under test would display its motion at a fixed alias frequency like 5 Hz or so. I could tune it over about 1 - 10 Hz. It was great for frequency sweeps. It was confusing and fascinating at the same time. You would hear the drive frequency sweep while the motion rate was constant. Great fun and very convenient. You could spot critical resonance modes quickly and not miss any of them. I have exactly the same driver you showed and some larger ones like it. We use a 700W amp to drive them.

As a young engineer I had a frequency counter based on RTL logic. one day the pass transistor flapping around in the breeze leaned over and applied unregulated DC to the logic and poof. A while later I asked the a Fairchild field engineer that was visiting my company if he could get me the obsolete logic. About a month later I found a jewel box on my desk with 40 or so RTL chips. I tracked him down to say thanks. he said "just thanks?" he told me to take a look at the devices again. They had date codes of a week earlier and had been hand packaged in ceramic packages with extra epoxy oozing out on all sides. he said it probably cost Fairchild $10,000 to make these for me. i mounted the regulator and put a crowbar on the VCC rail.

For those on a tight budget or time contained project the "Womens Health & Personal Care" category on Amazon has somewhat equivalent products for a fraction of the cost, they also often come with excellent ingress protection so you can do small product ingress testing under vibrational modes, but good luck explaining your need to the purchasing department. Please don't shadow ban this comment RU-vid.

Hey Dave.. Please repeat this with some new TO-220s, one flapping in the breeze, one down the the shoulders of the leads, one staggered pin arrangement, and one where "somebody had fun" as you often quote, gunked down to the PCB. It'd be good to get an appreciation of how much more securely the different mounting options work.. Not much point in trying a bolted to the PCB/heatsink version. I was soooo expecting a timelapse/ I'll leave it overnight video waiting for the failure, this happened much more quickly than I expected.

I used to use a larger version of this to calibrate electromagnetic vibration sensors for testing Rolls Royce turbine engines. It was driven by a vacuum tube amplifier with 4 807's in push-pull parallel. Driven by a good old HP 200 signal generator. It used an electromagnet controlled by a Variac. A Bruel & Kjaer reel to reel was used to record the engine tests. A vintage Nicolet 446 spectrum analyzer did the analysis. The boards inside were all wire-wrapped TTL logic This setup ran for years with no problems except sometimes you had to whack the Nicolet to make it work. This was in the 1980's. There were no airplanes crashing or natural gas pumping stations blowing up so I guess it worked. At least the vibration tests were accurate.

The first company I worked for after leaving college made these, the size of houses, to test aerospace parts. They used 50Kw audio amps to drive them, like they used to use in football stadiums. Which consisted of hundreds of transistors bolted to water pipes in parallel. The most amazing thing about them was that everything and I mean everything would hit its resonant frequency when we did the test frequency sweeps. Even your vocal cords, if you kept your mouth wide open you would make sounds that you had no control over. Also the tube ceiling lights made from fine glass would flex by a couple of inches without breaking.

I remember using these with PCBs and strobe lighting to actually see how the loaded PCB distorts (perversely testing PCBs for Frequency Response Analysers) . The tall electrolytic caps would appear to sway about like skyscrapers in an earthquake. We wouldn't just use frequency sweeps though, we had recordings of road vibrations as felt in the boot (trunk) of a car or in the cargo hold of an airplane. Fun times!

We used to use them to simulate human breathing into an oxygen cannula. Our products would sense the patient’s breathing via the pressure change in the nasal cannula and deliver a pulse of oxygen at the beginning of inhalation. We would use this in production to calibrate the trigger threshold. At least that’s what the modification could be used for. Great video. Brings back some old memories 😁

If AvE was reviewing this it would be a double-entendre fiesta

You just demonstrated why the Air Force teaches the "High Reliability Soldering Techniques" course that I took 40 years ago. It stressed making solid physical connection and not using solder to bridge gaps because of vibration and thermal movement. I spent the last 30+ years as a civilian shaking my head at the bad soldering techniques in all the equipment I've repaired.

Now I know why the silastic goo is always on larger through-hole components! Thanks Dave, for the enlightenment!

This very thing happened with transistors on Stern pinball boards mounted underneath the playfield. They had a kit they sent out to owners that contained plastic separators and tie-wraps to fasten the transistor so it wouldn't fall off from the vibrations.

Built a shake table with Aura Bass-Shakers and a basic stereo amp and IPhone app for sig source. Had to convince my boss that a 1k pot would be a better choice rather than a 10k pot. Even though the trimmer pots were staked, the 10k trimmer pot changed value enough to throw off the calibration. Tested phase matched cable sets for 1.5 GHz and sometimes they would also change enough to no longer be matched or would fail completely. Did not take much power (10 to 20 watts)at 20 Hz to 1KHz to get the table shaking. Different wave forms were cool to watch with a cup of water on the table. Cost about $200 in parts and pieces to build and was EZ PZ to build. Another good vid Dave!

Wow that was really interesting. I remember when we were calibrating the equalizer on the sound system at my church and we were sweeping the frequencies and found the resonant frequency of the room. It was the weirdest thing. I was walking around and could feel and hear the spots where I would be in standing waves, it was the weirdest thing. You would hit a spot that was super intense and loud, then hit a spot that was virtually silent. We turned it off because the wood panels on the walls were literally shaking and probably would have eventually shaken loose. We definitely turned that frequency way down on the equalizer lol.

Car audio amplifiers often go down to 2 Ohms and below, which might be ideal for this transducer. Great content and experiment, love the channel. Cheers!

I recall that back in the stone age, one of more frequent shake table casualties was large axial-lead electrolytic capacitors. You learned pretty quickly that those buggers need to be tied down--usually with a cable tie that went through the PCB. It was also interesting to see which would fail first on CRTs--the glass envelope or the electrodes inside... Good times.

A lot of people call them 'voice coils'. I was doing the vibration test on a product at a test house that had a 'car' sized shaker . one of their engineers hooked his bass guitar to it's 10,000W amp for 'testing'

I used to use these - and much bigger versions for shaking instruments. Talking of Bruel & Kjaer I also calibrated microphones with their pistonphone. It was a very accurate business, requiring a measurement of atmospheric pressure to offset the measured level. And Royston is only about thirty miles from here.

by the looks I would say the shaker tested itself well

"mystery device from the bunker" sounds like my old days around 2004-2010, when I built vacuum tube electronics (some amps, a compressor-limiter etc.) for myself and a few buddies, and labeled them "Vault-Tec Electronics". Gives a good idea where I got my inspiration for electronics design, and getting interested in tubes in the first place :)

Another vibration sensitivity you will see with analog circuits is offsets induced due to flexing of the die inside the package. Once had to rotate a 14 pin dip thermocouple amp 90 degrees and add some mounting screws to reduce its sensitivity to the pcb flexing.

I work in a 60 year old aerospace company, up until this year we were still using a full Ling made setup for vibration testing. Those things are hard to kill lol

Wow. That was really interesting. Never thought it would happen. Thought flapping around in the breeze was just a saying, but to actually see it happening. Would love to see a shaker series now.

The ring that keeps the armature centered is called a 'Flexture'. On larger shakers, they use optical sensors and air bags that dynamically inflate/deflate depending on mass and keep the armature centered vertically in the stroke. They can also be configured for single-shot where you start at the bottom of stroke. We have also used 2 shakers and controlled the phase relationship. For serious vibration testing, a MAST (Multi-Axis Shaker Table) is used where you can control 6 degrees of freedom.

When I worked for Vipac Engineers and Scientists, we had a Ling 10KN shaker and Ling 16KW amplifier which, I worked on regularly. Wasn't as good as the B&K shaker though. I used to calibrate accelerometers using B&K charge amps, was an interesting job.

Been watching for years, just wanted to say thanks for the awesome videos.

I really liked this video. Didn’t know such thing existed. Very fun and entertaining.

Great stuff! I've missed your longer videos where you really dive into something and do practical tests.

Great Video. Thanks for going thru the explanation.

Thank you so much. Those are certainly things to look out for.

Fascinating on many points! Thanks for that.

Always fascinating to discover another vital but uncommonly known industry. Thanks for sharing Dave!

Awesome to see you demonstrating a shaker! I work in the industrie developing the amplifier systems delivering sometimes more then 1000A to the shaker. Very cool to read all the comments about the different usecases and what experiences you all made with such systems.

17:55 That sounds exactly like Marty McFly pumping up the volume on the massive speaker at Doc's home.

This bring back memories of when I worked for Racal. We had a 1KW Ling Altec vibration table. System came with a strobe light so you could easily see the big ceramic capacitors fly off the boards. One of the PCBs I recall used components that were all identical cubes. So the whole assembly was a solid block.

Great vid, Dave! I love the new way you do the text overlays in this video. Very shmick!

Dave, This caused some memories to perk. Used to work on Ling 8016 amps and D300 shakers. The amps were good for 80kw with 275A field coil. The shakers would make 15k foot pounds of force. We killed them every so often. Long ago and far away. Be well there. Mike in Virginia Beach VA

Thanks - I learned something totally new today!

This is really interesting, I'd be interested in another video about this 👍

"That's what she said" is the unexpected touch that a fan of The Office is going to appreciate! :3

Very cool Dave, love it

The test is called experimental modal analysis. The goal is to measure the frequency mechanical response (acceleration) of structures under controlled sinusoidal excitation (displacement). It is strongly connected to the eigenfunctions of the mechanical wave equation. The goal is to find any ressonances and compensate using dynamic dampers.

We have a small shaker system, from memory is was a cube of steel about 1ft square and it had a couple of shaker motors fixed to it, so you could apply the vibrations in two planes. We used it mainly to look for issues in the cases and metalwork for the equipment. The steel block had various mounting holes and slots so that you could bolt the item down to it. With an added strobe you could easily see the metalwork moving, in some cases an inch or more. so you soon found out where additional fixing was required, either to the electronics or the actual metalwork. Wired up the the side of the control cabinet was the remains of one of the output tubes. I have no idea now as to the output power, but this tube was about 18 inches long and 5 or 6 inches in diameter, it must have been a couple of thousand watts or so. The tube had a long crack in the side, There was a pair of these in push-pull for each motor. Andy

Obviously it's a turboencabulator.

I also remember spending many hours getting a particular Defense product past " shake and bake" testing . We used large tables with random vibration sometimes by itself and sometimes while the product was in the temperature chamber.

That was great! 😂👍 You've got it in video! I'm too, before that, seen only results of shaking as broken legs near packaging, lose solder joints etc..

That part was installed exceptionally square to the board. In every piece of consumer electronics I've disassembled they're all leaning every which way. It'd be interesting to see how different angles affect the result.

18:22 reminds me to the times, when i tuned vibratory feeders. Nice video!

In my dayjob, I have to design for vibration and shock as well. I design spacecraft (satellite) electronics. Stuff needs to survive the shocks and vibration of launch. Our shakers are a lot larger than these, but the principle is the same. A lot of care is put on designing connector or wire interfaces with strain relief and proper mounting to PCBs. Shocks can rip SMT connectors clean off PCBs. Doing vibe analysis is an art form and some times it is counter intuitive. e.g. using glue / celastic to keep connectors from moving might affect the thermal expansion reliability, and lower the overall reliability. It's not simple at all!

BTW. Dave, did you hear about math-involved image/video processing techniques called "motion amplification" which allows visualize vibrations which are normally too small to be noticed by just watching video?

awesome vid dave

It looked like the resonance peak was moving when you turned up the amplitude the first time around 18:30, the tab deflection visibly decayed over a few seconds. I assume the material properties were already changing due to fatigue. Very cool demo,I always figured this was an effect that set in over like months of high vibration, not a worst case of several minutes.

I think Bill Haley and the Comets had one of these firmly in mind when they wrote the song "Shake, Rattle and Roll"!

The problem is often, how much vibration tolerances are enough? One product I worked on, we vibrated to the small PCB-trafo jumped off, because we have never seen that failure from the field. So we assumed, if the product could survive until the trafo got released, it could survive what the world would put it through...

This was manufactured in my small home town of Royston, Hertfordshire! Incredible! I knew we had quite a vibrant industry here back in the day, but it’s mostly died off now, aside from Johnson Matthey.

never seen such a thing. Great experiment

“That’s what she said?” - You tell her be careful she's liable to chip a tooth!

I worked for a company that put products in F1 cars and they would shear components in a single race or practice session.

Nice to see you have some fun. I have to perform vibration tests on a missile control system that is about 2 feet cubed and weighs 70 lbs; the shaker is nearly as big as a car.

Mr. Ling's first major business foray was to bid for a contract for shaker tables. He was thrilled with the outcome, and told people that the only customer he wanted to do business with was the government.

I have seen a very interesting application of this: In WW2, I think, magnetic bombs were made to explode when the metal bottom of a ship's hull approached it. This was defeated by DE-GAUSSING the ship's hull by 'degaussing engineers'. Then the opposition created 'sound bombs' set off by the ship's engines. The countermeasure for this was a pyramid-shaped "speaker-like" device that used a large underwater oscillator very similar to that oscillator. These under-water "speakers" generated far-range water oscillations which could trigger the explosive before the ship was too close to be damaged. PS I am always amazed at the clever engineering inspired in war! ... remember the air balloon bombs with the 'dropping weights sent to America via the Gulf stream.

My high-school work experience placement was on premises for shake and insulation testing of power station transformers for high risk installations in earthquake zones. That was a fun week!

Very interesting!

As soon as the buzzing was able to be heard, my missus came running over to see what I was watching.

Never knew about these. Very cool to see

Yep - I work in the industry for one of the major players, but I work on DSAs and Vibration Controllers. We have our own shaker lines too; and I actually have that very shaker sitting on my desk that I use to test our vibration control software! For anyone who is wondering, a tiny shaker like that will run you USD ~4-8k, plus another 1-2k for the amplifier. Nowadays these small size shakers are mostly used by Universities for teaching, or medical device companies who have strict standards they need to abide by. As Dave mentioned small PCBs' dont get tested much as their dynamic properties make them less susceptible to vibration damage by common vibration environments (transportation, etc); but larger PCBs do go through more rigorous testing.

I have been liking the new graphics you have been putting on the vids

That's adorable! I work in the aerospace industry and our older vibe tables are are the size of small lorries. The new ones integrate vibration and temperature in a single chamber.

we used to do standing wave experiments with these equipment..totally loved it..

Suddenly I am reminded of cheap RTC modules where the clock crystal is a metal cylinder held to the board by 2 thin radial leads. There's usually a solder pad to attach the case of the crystal to it, but it's almost never actually soldered to it. Seems that it would snap off quite easily when subjected to such vibrations

If i could give you a bigger thumbs up I would. Would love a PCB dynamic testing series.

NICE FIND!!! You found yourself a Flux-Capacitor!

I thought it was a seismometer. It's the opposite of one. Learn new stuff every day. Thanks Dave.

When I was an electronics tech we had a shaker as big as the biggest one you showed, we shook the heck out of parts while examining them with a strobe light to see how well things were dealing with the G forces.

cool stuff!

I learned about those years ago doign a tour of Catapillar with my father. They said they were using 2kw ones to test d9 tractors... I only saw the steel plate it was attached to.. now I get an idea of what those look like.. thansk Dave!

That was an amazing video. Regarding the adapter: I could also see it being used to create a directed, defined sine wave to test response frequencies of pressure systems. The tubing can cause non-linear effects on the amplitude and phase during transient pressure gradients compared to the actual measure point. With the shaker you would be able to experimentally determine the transfer functions to correct the errors

Used those for airbag diagnostic module testing in a previous job. Simulate a crash. Fun stuff! The mechanical resonance is critical for test.

"I can play with this all day"..... "that's what she said!"

In high school here in the states, my electronics teacher was David Bellaire... who invented the Tetrode. (May he rest in peace) - We got a tour of the Honeywell satellite plant north of Pinellas Park. They made BIG military sats..and had an immense shaker table. In addition to the usual sweeps and so on, they used a large bank of high fidelity amps to drive the thing.. Beethoven, Strauss (Also Sprach Zarathusra however it is spelled) and a ton of other goodies to make sure the sat would survive launch. Capable of moving a bunch of kilograms. not GREAT high fidelity, but I had no idea that various classical and Jazz goodies were used to test the car sized (and medium truck sized) sats...

Small shakers are also good for getting bubbles out of mixed epoxy resin.

I worked in electronics repair for a few years and yes I have seen TO220 and other parts break solder joints. That is usually the first place you want to look.

at my last job we bought a small shaker table second hand to measure vibration response of a motion-compensated airborne camera. after a while something in either the shaker or its power amp died (we actually sent the amp back to the manufacturer to replace some components but it didn't fix the real issue). so we found a local university with a packaging science shock and vibe lab, which was nice because their bigger pneumatic table could handle much larger assemblies. they also had one built into the floor that was the size of a car, and a few other instruments like drop testers.

Buddy of mine worked at JSC in Houston and rebuilt the amplifier racks and renovated the huge sound and vibration testing lab rig originally built to test Saturn V rocket parts. He is retired now.

I repaired digital clock and radio in my friends car. Both had cracks in solder joints on SMD components. Radio had obviously unsupported part of PCB where cracks occurred.

Nice video clip, keep it up, thank you :)

Nice demo!, I calculated the fundamental vibration mode of the TO-220, considering the dim tolerance, the resonance should be between 60 to 90 Hz, very close to the range where it showed high vibration in the video and broke.

I feel as though I am going to learn a LOT more from watching you than what I will learn from my Electrical Engineering courses. Hahaha

The HALT machine at our work uses pneumatic actuators in various axis to do the shaking. We use a combo of that UV sensitive glue and accelerometer wax to hold the accelerometers in place. That's a leur fitting, so yeah, it was being used to send pressure impulses to something. Maybe life testing pressure sensors.

These are cool. Combined with high speed imaging and Euler filtering, small oscillations can be amplified to see minute motion in an assembly, helping to identify potential modes of failure without destructive testing!

That one is so cute. Never knew they made them that small. I am currently operating a significantly larger, multi-axis table, where we shake aircraft communication gear. 6G RMS of random vibration, from 20 to 1000Hz.

We used one of these with a similar rubber membrane/ tube interface. It was for testing the consumables for urology diagnostic catheters.

Well I guessed this completely wrong pretty cool piece of test gear.

This explains the silicone/glue on those big capacitors and inductors.

Great video, a side by side comparison with the more sturdy staggered leads would be a nice test. Perhaps solder the worst 555 led blinker with TO-220 regulators and mosfets. Then with the circuit working find a good resonant frequency to shake it to oblivion. I didn't think shaking components like this would be so enjoyable to watch.

That was fun and educational :)

i used to do a lot of environmental testing of military electronics at Avco labs. They had shakers that could handle rockets and medium tanks. A lot of the smaller shakers were vacuum tube based, they were all water cooled. We made power supplies and they had to undergo all kinds of qualification tests, we used strobe lights so we could watch things twist and bend when you hit a resonance mode. Ive seen 3/16" thick angle braces that secured heavy transformers to a chassis crack and fail during a sweep and dwell test. One day i wandered over to the next bay and they were testing a USAF hydrogen bomb - luckily the trigger had been removed.