"As Bill and Dave intended". "No resonant cavities were harmed during the filming" Both absolute gold. I have HP equipment dating as far back as the 400C voltmeter. Love seeing your restorations / repairs.

@CuriousMarc

11 ай бұрын

Ah, the famed HP 400 VTVM (Vacuum Tube Volt Meter) series! I have a 400E that I restored off camera, but the restoration of the HP 410C voltmeter restoration will be on video soon, promised! Mr. Carlson has a couple episodes on instruments from that series too.

@antronargaiv3283

9 ай бұрын

@@CuriousMarc I'm waiting for that 410C restoration. I was given one and I think one of the neon/photoresistor pairs is non-functional...there's an ominous "X" on one of them 😞

@CuriousMarc

9 ай бұрын

@@antronargaiv3283 Same as on mine. But easy repair fortunately.

With how HP or HPE operate today it's refreshing to see a piece of their hardware you can use without 30 licenses attached to it costing you an arm and a leg.

@janosnagyj.9540

11 ай бұрын

Yeah, that hardware did cost you the same body parts back then 😅

@TeslaTales59

11 ай бұрын

And make you create an account just so you can use your own scanner!

@antronargaiv3283

11 ай бұрын

@@TeslaTales59 You just need an older one :-) MY Laserjet 5 don't need no steenkin' license!

@christopherleubner6633

11 ай бұрын

Back in the day this was about 5 grand.... in 1060's dollars.

@jagtan13

11 ай бұрын

@@christopherleubner6633 "1060" dollars. My goodness!

The "Do not tamper" warning makes total sense for the time period. HP had to carefully calibrate the units, and to assume that even government labs having the necessary equipment to carefully retune them would have been foolish. But I am sure they were disassembled and cleaned any way, just that HP took no responsibility for their accuracy after.

@SeanBZA

11 ай бұрын

Cleaned and repaired at HP on every trip in for service, most likely by washing in chlorinated solvent to strip the grease, and then putting new grease on afterwards. Likely the original ones used whale oil as part of the lubricant, as it has superior properties over the common petroleum distillates used then. Thus the change to different greases and lubricants in the 1970's, when whaling was banned. One of the reasons you find 60 year old tape is perfectly fine and usable, but tapes that are under 50 years old need to be baked before use, and then you get exactly one chance to play it out, before the oxide layer falls off the backing plastic film.

The "perspex" material is actually called "Rexolite" and is more like solid polystyrene. Relatively low dielectric constant (usually around 2) and very low loss (tan-delta). It also has very low moisture absorbtion, commonly used in microwave applications.

@w9gb

11 ай бұрын

I use different dielectrics for Coaxial capacitors. Polyethylene or polypropylene tubing and aluminum rods/tubes make nice L-C traps for outdoor antennas.

@itsverygreen532

11 ай бұрын

@@w9gb Yep, at HF there are many suitable materials, I use commercial PVC pipe a lot for HF stuff, but in very high Q kit and professional microwave stuff, you often find Rexolite used. It has a very distinctive look and feel, once you've seen a lump and identified it, it's easy to spot. Commonly used in "dielguide" feeds on dishes, with an aluminium cassegrain reflector.

@CuriousMarc

11 ай бұрын

Another commenter suggested it could be Zerodur too (a glass material that has the very same look). I thought the same, but apparently it was introduced in 1968 which would be too late. I'd have to reopen it to be sure and test hardness, but Rexolite seems very likely. Thanks for the tip!

@itsverygreen532

11 ай бұрын

@@CuriousMarc Definitely not Zerodur ... that is a very heavy glass, commonly used for telescope mirrors, very difficult to drill and impossible to tap! Rexolite is much lighter. You will commonly find Rexolite used in HP stuff, they used it a lot for high voltage components. Once you recognise it, you'll suddenly reallise how much of it you have seen, widely used in military radar and RF stuff, RF coil formers etc. Really enjoying the series, I have "a bit" of HP equipment, power meters, spectrum analysers, noise figure meters. My favourite piece is an analogue vector voltmeter. You should do a video on how HP made the scales individual to each meter, strange but true HP fact! À bientôt!

I could not help to notice, as a tech (retired), that many pieces of tech equipment you've shown I used on telecom equipment. Brings back memories,....

I'm on the other side of the world (of CA that is) and Marc always manages to post his latest video during my lunch brake. Yay!!

@Chriva

11 ай бұрын

Same same :) Perfect timing every time lol

3:30 I am not an EE, but I do think I "get something" out of these lessons on RF and even just basic Physics Eletro-magnetism fundamentals. 👍We don't need no teardowns of Apple Vision Pro.! No way man. Gimme a teardown of this sweet ol' analog HP 5245L freq. counter!

@cpufreak101

11 ай бұрын

same, I'm nowhere near an engineer and I learn quite a lot from these videos. i'm also sure it's easier to learn with these older machines versus a modern device where it's just "traces go into proprietary box of black magic"

@chefchaudard3580

11 ай бұрын

I'm a retired EE. And RF was always kind of magic for me. So, we are on the same level here!

Every time I watch your videos I instantly go to eBay even though I have modern test equipment these videos make me want old tech

Ah yes, the SRD. The tool of choice for generating Gigahertz frequencies, in the 1960s and for at least two or three more decades. I have a rubidium clock source made by Datum Efratom in the late 1990s and the synthesizer generating the 6.8-odd GHz representing the hyperfine transition that is the atomic reference for the output frequency is basically using the same principle, a SRD comb generator and a resonant cavity to pick out the correct harmonic.

Yay! I have NO idea what any of these instruments do but I am fascinated by the video documentation of their repair!

Very cool repair. HP sure knew what they were doing.

I think that heterodyning is my favourite RF trick, and I've never seen a more beautiful implementation than these plug-in modules. Very cool!

“CAUTION: DO NOT ATTEMPT DISASSEMBLY OF CAVITY" - challenge accepted. 🥸👍🏻

@ronjohnson9690

11 ай бұрын

CuriousMarc wins again!

@genericdynamics6618

11 ай бұрын

The emoji cracked me up

@Chiavaccio

11 ай бұрын

👍👍👏

@williamsquires3070

11 ай бұрын

Yes, this is a dog whistle to every hardware hacker, hobbyist, and RF/Microwave aficionado out there to open it up. Because, who doesn’t like looking at some RF black magic; the darkest of dark arts (and we know this thanks to CuriousMarc’s Apollo series!) 😅

@thehighwayman78

10 ай бұрын

Cavities are for filling, not disassembling... Ehm...

The only thing wrong with these episodes is there is no mystery. Marc ALWAYS figures it out and fixes the thing. Fabulous!

@dieSpinnt

11 ай бұрын

Hmmm, I think I spotted something very mysterious: That you can't see the mystery or better the fascination of these old and wonderful designs and how explaining and fixing them comes all together to a big and consistent whole. Just kidding...at your expense:P My apology! If you look from a slightly different angle, then there is enough mystery that is later revealed in a very entertaining and exciting manner:)

@glennstasse5698

11 ай бұрын

@@dieSpinnt no offense taken. I feel the same way as what you described. Everything here seems like black magic to me. It’s voodoo! It’s AI without the A!

I absolutely loved this video. I am always so impressed at the technology of that period. And especially how both HP and Collins Radio implemented it so skillfully. Thank you very much for such a well done video.

A cavity search always makes for an interesting KZread video! 🤪😅👍

Can not imagine what it took to manufacture and calibrate in the 60s though I often hear that it can be good if not better than today's workmanship. What I do know is that aerospace funding had a massive boost in the late 1950s and early 60s. I wonder why lol. Great video as always. Off topic, I have a 10590A which is not in use. Planned to get one of these oscillators to test it in. Came with my 5345A that runs a 5355A compatible with its 5356D attached. What I love about the 5345A isn't the fact that I can use my 11970W mixer to it but rather that it actually has someone's name (I'm assuming they did QC) inked on the display module when I repaired it. Simple faulty SCR on the a power module but decided to fully tear it down to rid of the dust bunnies. I took care not to remove any markings of any kind. These instruments were evidently made with care after all. To see the names and markings adds personality imho.

It's a very satisfying process taking a mechanism apart, cleaning it, lubricating it and then putting it back together again. I always marvel at how something which didn't work properly or at all now functions smoothly, everything rotating and clicking. It's like magic. Great job, well done. Thanks for the video, Marc!

Wonderful RF engineering where shape and form are function at these frequencies.

Could you have used a lathe and dial test indicator to true the female part and then put the dial test indicator to achieve the same concentricity? All in all it's great that it worked out for you.

I think you and Ken should try and design a K-band plugin- 18-26.5GHz, using some more modern components.

[slaps top of retro HP equipment] 'this baby can fit so much physics'

As someone who arguably watches too many automotive repair channels - next time you are faced with gears coated in old grease and stuck screws, try recruiting your favorite penetrating oil (or at least WD40) and a quick trip to the oven (or perhaps just the outside, at this time of year in California). I imagine that should make disassembly a whole lot less stressful in such cases. BTW, instead of just generating a frequency comb, you can also use such a pulse train to feed a sampling mixer that can than serve as the phase detector in a PLL. This way you can lock a continuously variable oscillator to a fixed frequency grid, you just need to limit the PLL VCO pulling range so that it can only do fine-tuning. This concept even briefly made an appearance in the consumer space by way of a few high-end FM tuners of the late '70s / early '80s. The point was combining the good frontend selectivity, linearity and low phase noise of a mechanically-tuned affair (not to mention lovely knob feel) with the accuracy and lack of drift of a PLL job. These concepts became redundant as people figured out how to make lower-noise PLL VCOs and gain distribution improved. The first instances of oscillator grid-locking I could find even predate these HP units. The Siemens E311 communications receiver (1960) did this for its 1st LO, using funky electrically permeability-tuned inductors for fine-tuning no less - the varicap diode had yet to be invented, so tweaking inductance via core saturation was the next best thing. I presume HP went with the "filtered comb" approach in order to keep size and complexity of this compact module down, alongside the large relative tuning range required.

EIGHTEEN gigahertz? What kind of black magic grey beard wizardry did they use to build that in the 60's!? I bet it even involved virgin sacrifices.

@davidverbeek4849

11 ай бұрын

and goats. goats and virgin sacrifices, maybe even virgin goat sacrifices

It's amazing how clever and advanced engineers in the 60s already were! With all this witchcraft and rocket science they could have built spacecraft and flown to the moon... Oh, wait - they did... 😂😊

@OscarSommerbo

11 ай бұрын

At the time, RF was the bleeding edge, and we are seeing the peak of RF trickery. Digital circuits rapidly overtook analog/RF tricks, with much more robust and rugged design. You can even see the beginning of the digital era in these instruments, all those discrete components, and no vacuum tubes. Well almost no vacuum tubes.

@kaitlyn__L

11 ай бұрын

@@OscarSommerbo I love diode logic, and you can really see how they got from here to there.

Did I just see something impossible proven to be possible? 😮 The accuracy of this 60’s magic is hard to believe. I’ll watch it a couple more times. And a warning to the other stuck plug-ins: Resistance is futile !!

RF Magic. Thank you for this beautiful Teardown.

These levels of RF just boggle the mind. When you start dealing with 'cans' as coaxial lines, it just amazes me. And that you were able to disassemble and repair this is amazing. (not to mention you just 'happen to have' the signal generators to test this stuff :) )

@thesteelrodent1796

10 ай бұрын

at this point Marc seem to have just about every piece of kit from the 1960s and 1970s HP catalogues =D

I used one of these in the 1980s in a HF transmitting station and used/rebuilt tunable cavity resonators on 100-500MHz landmobile kit during the same period (the Q on those cavities was so high that their bandwidth was less than 10kHz) Reassembly of the cavity is highly sensitive to electrical continuity of all mating surfaces - there are large RF currents flowing on the internal cavity surfaces around the top end - right where your cap is. It matters more when hanging these after transmitters (heat losses) but it hugely affects Q if there is corrosion or poor conductivity across the surfaces. Those tarnished silver faces need cleaning (immersion in saltwater along with an aluminium strip will work best as it's a non-abrasive method - clean & dry thoroughly afterwards) The robust design and warning are because these were intended to be used in military environments and army/airforce bois have a tendency to be rough on their equipment. Reassembly with the dial markings being correctly aligned is "difficult" (one of my ham-fisted cow-orkers pulled our one apart. It never worked properly afterwards)

What a great job you are doing Marc! You explain what you do and how the equipment/apparatus you work with in an excellent way. I get very excited every time a new @CuriousMarc video is published. Why this channel doesn't have even more subscribers is a mystery to me. Thank you so much!

I loved working at HP, and I enjoy watching these videos almost as much! Simply wonderful.

I’m always amazed by these fix ‘em videos. 👍 Plus, I feel like I’m learning something. Merci, Marc!

Another 30 mins of fascination thank you!

Wonderful video of both the breakdown and explanation of function. Well done. I appreciate your efforts.

- Do not attempt to open! - Open or do not open, there is no attempt! We open!

Later, frequency counters were equipped with a YIG-tuned filter that filters the incoming signal instead of the local oscillator (LO). Then, the filtered signal is sampled/mixed with a pulse of approximately several hundred megahertz. Also, manual power metering is done using the microcontroller to search for signals within the 1-18 GHz range. Very good video.

@like_cabezon3810

11 ай бұрын

It seems that the newer HP counters like the 5342A didn´t had the YIG filter but other diferent models such as the EIP 545,548,585 and 588 have those tunnable filters

As always wonderfully explanation thank you

Ah yes, the black arts of RF and resonate cavities! Another excellent repair Marc! *(...and you didn't even have to break out the Smith charts and protractors!)

Looking forward to the 8663 repair...love these things. I have 7 in the lab.

Amazing technology from the year I was born! Great work, Marc, on restoring this masterpiece.

you just saved me a million hrs figuring out how to repair mine, just scored the same counter 5245L and the same 500MHz plugin 5253B mine is also a bit stuck, I was going to figure it all out and explain it make a video about it, but now no need to add more bytes to the world of internet, since this video explain it all :-) the funny thing is the 5245L main counter unit exist in several versions looking a bit different on the outside, now i got both versions, I also got one with 5267A plugin a time interval unit, that one is on my YT in case you like to see it.

Marc I'd watch you fix a toaster

Fantastic! RF is a magic I will never fully comprehend. And it blows my mind even more they were able to master it to that level almost 70 years ago.

Those nixie tube displays have such an awesome look.

OMG I don't understand much of anything about all the technical stuff yet am hooked on this channel and all the stuff they fix 😁😁😁

Such beautiful engineering. A work of art.

As always a pleasure 😀

Bloody amazing.

"This set is equipped with a safety interlock. Do not attempt to defeat its purpose." I remember ignoring that all the time!

Really interesting! Learned alot again! Thnx Guys!

Thanks, awesome. Luckily my 5253B works, and thanks to your video I don't need to take it apart to see what Bill and Dave are hiding from me.

@CuriousMarc

11 ай бұрын

Very cool. I wonder why I always get the terminally broken ones...

@clytle374

11 ай бұрын

@@CuriousMarc I normally buy the broken ones on purpose. But this one was luck in an auction. If it makes you feel any better the gears in my HP-8640B broke last week and I had to fix that. I spend most of my time on tube gear though.

My HP-8640B has one of these adjustable cavities. Except… it has plastic gears in the knobs and they haven’t exactly aged well. Great video as always!

Wonderful stuff!

Looking at the characteristics of step recovery diodes, I have to wonder how this effect was even noticed in 1960. You would have to be looking at the switching characteristics of diodes with equipment that had a very high frequency response.

@ferrumignis

11 ай бұрын

The harmonics that it would have generated would have been very noticeable, but direct measurement of the super fast switching would have been quite difficult I suspect.

@christopherleubner6633

11 ай бұрын

Apparently they noticed that some zener diodes caused RF interference and they went from there.

I wanted to call it magical first but actually those engineers were just geniuses.

I have one of these and also the plug in too. Mine was working last time I checked it. Must get it out and test it.

RF gadget with a boiler in the middle of it! LMAO! Good one, Marc! Oooo, transmission line calculations... break out the Smith Charts!

I thought for sure that disassembly would be a one way journey, but no, how could i doubt your skills! Splendid and fascinating work and a great video. Thank you

Wow! And amazing. I must say I get nervous and anxious when you take these marvelous instruments apart. We can only admire and be humbled by the engineering genius it took to deal with these high frequencies 60 years ago. Wow!

Superb series! Takes me back to an earlier life servicing equipment like this. Incidentally, I was watching a North Korea documentary and spotted an HP 5245 on the USS Pueblo (4:52 mark in this video: W_Z1oSINw-M) but it's missing the plugin module, nixies and knobs in other photos of it.

I suppose you could make a cone shim so the taper can seat on the bore, and that should locate it accurately before the tightening of the locking plate. If the gap is under 0.002" a paper cone might do.

The black magic of _The Cavity_ would make for a good legendary item in Diablo IV ...

HP came out of a shed. And obviously, there were a lot of very sharp tools in that shed.

@CuriousMarc

9 ай бұрын

The shed is 10 minutes from where I live!

I remember having to deal with the same solidified grease while servicing HP 200 signal generators in the 1980s

RF black magic, but with gears, and hand-cranked.

Pretty Cool

I have one question left unanswered : What is the purpose of rotating the diode and the antenna assemblies ?

@SeanBZA

11 ай бұрын

Providing a matching function, so that your antennas are exactly, or at least closely, matching the changing angle of the resonant wave, as the cylinder changes in length electrically. Keeps the signal input, mixer input and output at close to maximum for the electrical coupling to be most effective. Not really noticed on a fixed cavity, as part of the tuning process involves adjusting the various antennas used for injection and extraction to a maximum level, and locking them at that point. However on a variable one you do need to adjust the antenna orientation to match, so the mechanism to adjust the angles, and the 2 RF boxes on them that provide short length connections to the antennas, minimising losses in that area.

@CuriousMarc

11 ай бұрын

It’s a puzzle to me. I first thought it was to maintain maximum coupling as the frequency changes, but it can’t be. The E-field is always normal to the wall of the cavity regardless of frequency, so it’s in effect varying the coupling coefficient. Maybe to equalize the response or the Q of the cavity over the band? I dunno.

@alanbain1651

11 ай бұрын

@@CuriousMarc In this plugin the cavity becomes electrically very short at the bottom end of the tuning range (around quarter wave long at 500MHz and it tunes down to 50MHz right). In the lambda/4 case it's fair to assume TEM propagation and solve as a transmission line but in the really short case I seem to recall the field starts to be significantly distorted by the capacitor. I assumed this is why there was a need to rotate the antennae for optimal coupling.

@CuriousMarc

11 ай бұрын

@@alanbain1651 That must be it! The TM modes will have an electric component along the propagation direction of the cavity, therefore you'd need to tilt your coupling antenna to couple efficiently into that propagation mode. I wonder if there is a gradual transition from one to the other, and you end up with a TE00 + TM01 combo. Would be fun to model this in HFSS if someone had access to it. I tell you, you better know your math and your Maxwell equations to do microwave engineering...

As always a great video and I admire your RF knowledge and the way you film these adventures. They are very much enjoyable and educational as well. Thank you Marc!

Great video. How do the rf wizards account for the stub resonator properties also changing significantly over the operating range? At 50 MHz you’re quite far from l/4. Does the q-factor drop for these frequencies?

I've repaired a good few of these but never dared go inside the cavity. Now I'm wondering if the 8640A/B signal generator cavity looks the same inside (with the addition of the little fine tuning flag)... At least these don't have plastic gears, wait for the 5254A/B/C; when they become sticky they strip the gear teeth. The gear with the dial attached has 61 teeth which is a most annoying prime number when it comes to cutting new ones. I seem to remember I had to get out the oxy-acetylene cutting torch and make a new diving plate!

Kind of have no choice but to disassemble the cavity to fix mechanical issues. You will want to take lots of pictures and keep a fine tip sharpie handy 😉

wow, 18gHz (!!) fun facts: at 18gHz the time between 2 steps is only 56 pikoseconds. in this short time, light travels only 1.6 centimeters (or 0.66 inch)

Marc, Regarding fabricating an extender: I went quickly through all the relevant plug-in schematics I have (nine or ten), and I could only find but 10 (out of 50) unused pins on the connector. The TI and Prescaler plug-ins used quite a few pins. Have you ever seen a universal HP extender? I wonder where HP put the coaxial leads? Thanks for the video.

HP was awesome in the day.

Looking at the disassembly and how you did it you must have owned some boxes of Meccano as a child 😂

These must have been SO expensive back in the day.

Tnx,super hp Warsaw Poland.

That (then) greenish grease is also horrible in 1930s--1960s cameras, the focusing thread is almost always stuck and you have to disassemble it using gentle heat, clean it, reassemble with fresh grease and then you have to find the infinity stop again ..

"FOR THE LOVE OF GOD AND ALL THAT IS HOLY IN THE UNIVERSE, PLEASE DO NOT TRY TO SERVICE THIS UNIT." -handwritten sign on a big beige cabinet in the IT department of my college, c. 1994. It wasn't my department so I didn't ask.

The yellow glass block looks exactly like zerodur ceramic.

@CuriousMarc

11 ай бұрын

Ah thanks, I was looking for the name of the thing and could not remember it. It certainly looked and felt like Zerodur indeed.

@andrewlecouteurbisson7217

11 ай бұрын

@@CuriousMarc I'm familiar with its use in ring laser gyroscopes. It definitely seems like a case of "no expense spared" in this application. That said, I was astonished by the accuracy of the down conversion so I presume it was money well spent!

@CuriousMarc

11 ай бұрын

@@andrewlecouteurbisson7217 Another poster mentioned Rexolite, but the large puck felt like glass, not plastic. However the rod looks suspiciously like plastic, so it might be Rexolite. I’d have to take another cavity apart and look closer!

@y2kkmac

11 ай бұрын

​​@@CuriousMarc it sure does remind me of Zerodur, but Zerodur was introduced in 1968, does that timeline track? Seems a bit late but what do I know... The mystery deepens!

@CuriousMarc

11 ай бұрын

@@y2kkmac No, 1968 would be too late. Then the Rexolite hypothesis is gaining even more traction! I'd have to reopen a cavity to know for sure.

Not very relevant to this video, but: yesterday I met a 12-year-old girl named Nixie. I asked her if that were her full name or a shortened form of something else, and she said no, that's her full name. I said I had never met anyone named Nixie, but that there was a vacuum tube with that name, and she said "I know." Somebody out there is raising their daughter right...

“How do they get a counter to work on higher frequencies just by plugging in a gadget?” Me, who has seen lots of SDR tutorials on frequency division or multiplication circuits to get the entire spectrum within the limited range of the hardware: oh I know this for once! Edit: well, I was still surprised by the _implementation,_ if not the theory! It's good to show how cost reduction from earlier optimal designs isn't a recent phenomenon at all. Thankfully the drawback didn't affect end use in this case, but it always starts by making repairs more perilous! I could easily imagine someone taking off those final screws back in the day and getting in trouble, especially if they'd seen earlier units with centring guides and weren't taking their time double-checking everything.

The process of taking 2 frequencies and making 2 new frequencies, sum and difference is called HETERODYNING.

that's magic

Is this down-conversion similar to wadley loop?

can't wait to see the other plugins insights videos 😊

the black art of rf voodoo

If you form extremely short pulses with that SRB diode of the 10 MHz: - are the short pulses like a gate or do they add high frequency portions to the 10 MHz ? - do you only get multiples (harmonics) of the 10 MHz with the short pulses and no other frequencies? - if yes: on digital signals: do (extremely) sharp/quick signal flanks "only" create multiples / harmonics of the frequencies that are already in the base signal?

Nice 👍 21:04

* I just picked up an HP 3439A Voltmeter, then ordered the original service manual! I'll see if I can restore the beast...

@CuriousMarc

11 ай бұрын

Good luck for your repair! Go save it!

"the boiler in the middle" :D

Does anybody know why the drive and readout antennas are made to rotate as the cavity is tuned? That's really interesting. I wonder how accurate that part has to be. I imagine it is something like changing the length from the antenna to the nearest wall, if you draw a line perpendicular to the antennas ?

Wizardry on all levels

I just recently acquired a 5245L made in 1967. Works great, but some of the plug-ins I have could use some adjustments. Would you have the wiring diagram for your custom 50 pin plug-in extension cable? I’ve tried a few old 50 pin SCSI extension cables and while they physically fit, they do not pass the signals correctly. I must be missing something critical.

@CuriousMarc

11 ай бұрын

The only diagram I have is the one shown in the video. It’s all straight through, and the two coaxes at the end, as marked on the schematics.

@thequinnreapernovaco.7497

11 ай бұрын

@@CuriousMarc Excellent, thank you! And fantastic videos. They’ve inspired me to acquire a few of my own vintage HP counters and assorted gear.

Does it have an ad block plugin at 666Mhz?

@11:40 - In all fairness to HP and the vintage electronics, I would be averse to having a cavity search too. Just saying.

Why is there a video amplifier in there? Surely video amplifier is some sort of terminology I don’t understand.

@alanbain1651

11 ай бұрын

In this context it just means a broadband amplifier as opposed to a tuned amplifier.

@CuriousMarc

11 ай бұрын

I'm with you, it's very confusing historical naming. It's by contrast to an audio amplifier and a VHF/UHF amplifier. For wideband amplification to a few 100 MHz, it's called a video amplifier, even though it's not used for video at all! I suppose that was the first use such amplifiers at that frequency, so it stuck around.

A dead short, solid lump of metal is an inductor? RF hocus pocus I tell you.

@SeanBZA

11 ай бұрын

Tell that to a magnetron, where you have no moving parts, a glowing red thoriated tungsten coil as heater, and a pair of magnets, that makes roughly 800W of power, in a block of copper the size of a large hen egg. plus does double duty not only as a rectifier diode in a voltage doubler, but also as power oscillator as well.

Could you get away with soaking the whole bottom in IPA or something? to get it somewhat unstuck