CuriousMarc - 2024-11-08
With great difficulty, we repair our Patron-donated HP 115BR divider and clock, an instrument that was once used to synchronize all of the world's atomic clocks. It requires a bit of a fight, but in the end, we are rewarded with the most steampunk atomic clock ever! HP 115BR Playlist: https://www.youtube.com/playlist?list=PL-_93BVApb5-_7sWRxQ0on8vNy7_H-zxS Atomic clock playlist: https://youtube.com/playlist?list=PL-_93BVApb59F6V90OdcqVofqVWceR6Dk Link to the HP 115BR Manual: https://bama.edebris.com/download/hp/115br/HP_115BR_frequency_divider_and_clock_op_service_manual_1967.pdf Stuff that supports the channel: - Support us on Patreon: https://www.patreon.com/curiousmarc - Amazon links for the tools I use in the lab: https://www.curiousmarc.com/amazon-links - Channel merch on Fourthwall: https://curiousmarc-shop.fourthwall.com - Legacy channel merch on Teespring (I don't have everything transferred to Fourthwall yet): https://teespring.com/stores/curiousmarcs-store "Elevator Music" Credit: Crinoline Dreams by Kevin MacLeod Our lovely sponsors - PCBWay: fast turn PCBs, https://www.pcbway.com - Electro-Rent: https://www.electrorent.com - Keysight: test instruments: https://www.keysight.com - Samtec: connectors: https://www.samtec.com - R&D Microwaves: https://rdmicrowaves.com Get more technical info on the companion site: https://www.curiousmarc.com Contact info: https://www.youtube.com/curiousmarc/about 00:00 Recap of Part 1 01:45 Reverting to the original configuration 04:43 Schematics explanation 07:41 First regenerative divider 10:40 Magic "endless" phase shifter 12:46 Second divider not working 14:48 Debugging the divider 16:57 Tripler transistor weird fault 19:25 Our loopy circuit is cursed! 20:30 Second fault in the mixer? 23:20 It must be the transistor 24:10 It must be the tuning circuit 29:00 Maybe a biasing fault? 32:21 We got it, it's working 33:35 60 Hz reference repair 35:58 It's all repaired! 37:13 Atomic time, baby!
If I drink enough, my vision phases out the potato vision.
You were just early. Now it's up to 2160p.
Only with alcohol from potatoes
I watch everything on my phone, I barely noticed the potato vision.
@benjaminhanke79 I takes YouTube a while to render the higher res. If you just watched all was finished. NeillABliss was a bit hasty commenting on the quality.
@@bennylloyd-willner9667 Some of the video was shot out of focus with a comment over the top apologising for the "potato vision" (e.g. 11:18) - nothing to do with YouTube's processing.
You know, that generation of engineers continues to astound me with what they could do with so few options. How one can create a sort of “minimalist complexity” still looks a bit like magic to me, wizardry I say.
We often don't appreciate how good we have it.
Bad ancient tantalums?
Who would have thought!
Tantalizing repair.
I remember seeing an Amiga (late 80s/early 90s computer) for sale on Ebay where the vendor advertised that they had replaced ALL the capacitors as a matter of course!
Good old tantrum capacitors!
@@zh84 Sadly, this seems to be commonplace. Inevitably, it introduces new problems, as Adrian's Digital Basement found recently. He replaced the caps on a Mac SE/30 motherboard and in doing so accidentally bridged a 5V signal line to the 12V power rail. I've seen all sorts of other problems caused by recapping - reverse polarity, massively wrong value, under voltage spec etc.
This old RF jock thought 'bad caps" right away. If my semiconductors are good, every electrolytic/tantalum cap becomes the next suspect.
@@Zadster I have seen folk replace smoothing capacitors with much higher values "to make it better", only to find that the increased inrush current blows up the supply.
That tripler circuit (6:40) is at once crude and elegant: driving the thing so hard it distorts wildly then using the fact that a single ended circuit will have dominant odd order harmonics and picking off the third. So clever.
Hardware from this era was beautiful. Really enjoying this series.
New Curious Marc videos showing up in my feed always make my day!
As a 60 year old mechanical engineer watching this, please, please, please clean the mechanical clock mechanism as per the service manual. Do it before it is too late. The tight tolerances of the bearings and the gearing are being abnormally worn every time you start the motor. The clue that it needs to be cleaned is that you must give the motor a very strong torque to start it spinning. You should be able to start the motor by a simple twist of the knurled handle between your thumb and index. Also HP would never have let such a noisy mechanism out the door. It should be whisper quiet.
We know. Clock is clean. There is a bad bearing in the mechanism. It's very difficult to change, haven't done it yet.
@@CuriousMarcso maybe you Need a watchmaker in your team. 😉
Marc: “This is going to be interesting.”
Yes. Yes it is. 👍
"Miracle dividers" - I couldn't agree more. That 4 transistor divider circuit is sheer analogue genius. Thank you for another very watchable episode.
Four boxes in the block diagram, four transistors. Those were the days.
25:50 That's wild, the tripler is happily working as a quadrupler instead, thanks to its asymmetric single-transistor design evidently also generating plenty of even harmonics and not just the odd harmonics you'd get from nicely symmetrical clipping.
Oh, good catch! That's exactly what's happening.
Yes, I spotted that.
In the late 60s, I worked at a NASA STADAN station at Winkfield UK. We had a visit from the NASA calibration team. They flew around the world calibrating the test equipment. They also carried an atomic clock to check each station's clock.
I have absolutely no justification but I want one after seeing this video. The engineering is gorgeous, and that display is a work of art.
Thanks for the continued awesome videos!
Dr, you have no idea how much I like the content on your channel; The analysis, the theory he uses makes his video super interesting. I thank you infinitely for all your effort and time in preparing each video. A cordial hug from Mexico
Great video. I love your explanations, demos and your test equipment. Quite a project!
Thanks! I am feasting on short clips from your old NASA videos too to look for Apollo comms equipment, I hope you don't mind...
I must be weird too : I enjoyed watching the various frequencies on the scope! 😮
… and a blurry schematic too!😂
"If you follow the channel?" Of course I follow the channel!
Merci Marc , c'est quand meme fou de pouvoir s'amuser avec de tel appareils, quel chance !!!! un grand merci pour le partage c'est toujour un reel plaisir.
Thanks Marc for doing these videos, like everyone's comments those HP engineers and manufacturing infrastructure were next level.
5:40am & curious Marc. Breakfast and a cup of tea….perfect end to the week
37:56 I love that within the picture within the airplane they have a quad outlet box and three of the knockouts are knocked out on the side.
Nice work loop circuits always gave me a fit when I was working in electronics. Thanks for the video Marc.
Amazing bit of kit, transitional technologies are just so fascinating... love the germanium transistor mounts. Also, yours is the only channel which makes me want a noise blanker in the audio path
I once had an old transistor radio where the transistors were mounted in holes in the chassis with little rubber grommets. Another example of tube-era construction techniques applied to transistors. I guess transistors were expensive back then and deserved a bit of pampering.
Lots of early transistor radios had the transistors in socket for easy replacement - Zenith, for instance. Turns out, they needed it, because the transistor enclosures/"cans" were tin-plated and tin whisker frequently cause shorts, particularly 60+ years later.
Perfect Friday morning content!
A few good beers and 40min of HP goodness repair. That was a nice evening. Thank Marc.
I'm a software engineer who considered being an electrical engineer when I was in high school in the 1970's. I like your methodical approach to debugging the various problems without making unwarranted assumptions. It is similar to how I debug a misbehaving program or OS kernel crash. It's a shame that so few professionals in our respective fields seem to have good debugging skills.
Merci Marc, another great video.
Another great video. Please keep making them!
As beautiful as these constructions are, I'm grateful for the invention of PCBs when I see Marc chasing faults in this 3D labyrinth.
Salute Dr Paul Eisler
True, but nothing beats the smell of molten solder from the stone age 😊
PCBs and ICs are widely over-rated. You don't need them at all ;-)
You really do have the best toys.
At Curious Mark's™ "We've Upped Our Quality. Now, Up Yours"...
11:31 “Use your imagination to see this clearly” this would make an engineers life so much easier… 😂
This is super! A lot of creative engineering from 196s
Suspect the tantalums! Great job Marc. Love the point-to-point electronics, so easy to work on. That synchro motor is noisy... perhaps some Hamnmond tone generator oil is needed? I just bought some Kroil Microil, looks like the exact same thing... the mechanics sound a lot like a Hammond organ that wants oil!
Syncrho motor is fine, but there is a bad bearing in the clock mechanism. Replacing it is a bear though, you have to take all the gears out, so I haven't done that yet.
when working with transistors, grab'm by the DCs and the ACs will follow. Cool video, thanks.
Well said!
It's interesting that they reduced an oscillator to a mere ringing circuit. Some of the 80's game consoles included a crystal resonant circuit followed by a buffer amp for that same purpose, but this is the first time I've seen one that used feedback.
Wow, that world tour to synchronize clocks sounds fascinating, it's History, significance and all. Is there a documentary or an interesting resource on the subject?
37:56 Interesting how they fastened the seatbelts! However, it looks like the equipment was travelling economy class. That's a bit of an insult to H.P. equipment. Should be first class all the way!
At least the cabin attendants gave them blankets and pillows.
This device appeared in the recent Nova on PBS. Just for a few frames, but it was so obvious after having seen Part 1. Will try to get a link and offset for y'all.
Just watched it. Great episode on how quantum mechanics affects everyday life: https://www.pbs.org/wgbh/nova/video/decoding-the-universe-quantum/ . The HP 115BR appears briefly at 17:35, followed by the HP 5061A Caesium clock equipped with the later integrated Patek Phillipe divider and clock. Awesome science documentary, they are right up there with Veritasium. Or is it the other way around?
@@CuriousMarc Video not available for german users :(
And they strapped it in a seat on the plane!😂 Well, it would be a more gentle flight than if it were bolted to the floor.
Another great one.
That style of wet tantalum cap (TAA was a common type) were an absolute nightmare, they were used extensively in military equipment from the 70s and 80s and caused so many problems, the electrolyte could leak and, as it was sulphuric acid, highly corrosive. If they didn't leak, they often went short circuit and caught fire.
3:06 it's like electronic surgery.. Nurse... soldering iron! Stat!
Testing if the coils are resonant - I half expected you to break out a GDO!
What's the purpose of centiseconds markings on the wheel? For use as timestamp on short-exposure photos?
I figure the unit would be on long term/indefinitely hence the exclusion of an auto start for the dividers and synchronous motor but could one be added?
Ah! The second you said "tantalum" it became clear. Unlike most capacitors, the failure mode of a tantalum cap is a short rather than an open circuit. It would have flooded your mixer with a bias, my guess saturating the transistor or introducing distortion at the very least.
On a side note, bad tantalum capacitors is a common cause of the failure of many early PC motherboards. When you measure a short between one of the power rails and ground before powering it up, guess what the culprit is 95% of the time.
(FYI... typing this on my HP laptop)
Are the start switches duplicated on the outside? Or do you have to remove the unit from the rack and open it to press buttons and spin the motor every time you want to start it
sorry that I did not understand but, how originally this motor starts itself? is it that right now You give it a little twist that it can run on single phase, but to start itself does it needs a two phases ?
@richardlincoln886 - 2024-11-08
Question - the bootstrap startup process: click the button, flick the motor
That's all inside the case - you have to dismantle that box every time you get a powercut/cycle the power on the clock?
Cheers.
@phuzz00 - 2024-11-08
The main workings seem to be on rails inside the box, so I think you undo the two big thumbscrews on each side (labelled 'open'), and slide it out just far enough to flick the switch and spin the motor. Then slide it back in and screw it shut.
I guess you're intended to leave it permanently powered along with the atomic clock.
@CuriousMarc - 2024-11-08
Yes you do have to open it up to restart it. But the clock is supposed to be powered by the crystal source, which has one internal and one external battery backup (that's why the input power is 24V DC and it has no mains plug). We'll demonstrate that when we run it with the HP 106B. The clock is useless anyhow as soon as it stops, you have to realign it to an atomic clock no matter what, so in practice that's not a concern. What would be terrible is that a non knowledgeable person could restart it easily and you would not notice that it had lost atomic traceable time.
@paulstubbs7678 - 2024-11-09
@@CuriousMarc Yes it should only be restart-able by men in white jackets (or whatever time boffins wear) with lots of letters after their names, front panel button proders (as in every day domestic clock restarters) need not apply for these jobs.
@MarcoTedaldi - 2024-11-10
@@paulstubbs7678 you forgot the fancy pants! :)
@anthonylovell2271 - 2024-11-10
@@MarcoTedaldi they come with the jackets 🧐