Restoring an HP 521A Frequency Counter: Part 2

[@CuriousMarc]

Such gorgeous tube instruments! You can feel the counting. You can almost touch it! David Packard recalls how the counter was the first instrument to go digital after the war. Congrats on the progress.

[@UsagiElectric]

Thanks! The old HP150A has been paramount in getting some much needed debugging done. Slowly working on that goal of using nothing but full tube HP gear!

[@lindoran]

Your point to point soldering skills are on "point" I don't think people realize how hard that is. Excellent video as always 😊

[@UsagiElectric]

Thank you so much! Getting point to point stuff to look halfway decent is a proper struggle, especially considering how much more compact modern components are, but I think the axial caps turned out alright this time!

[@jimmy_jamesjams_a_lot4171]

¡¡THANK YOU for all of your efforts in troubleshooting and prolonging the life of those gorgeous pieces of test gear!! And then to upload videos like these? The value in sharing your fiddling around is huge! KEEP IT UP!!

[@sketchitoutstudios]

I love your videos. I don’t know anything about the capacitors or circuit boards but I think your videos are awesome to watch.

[@UsagiElectric]

Thank you so much!

[@gammaleader96]

The controls of the counter sound like they feel very nice. The insane amplitudes of vacuum tube gear always fascinates me. While modern receivers are totally fine with microvolts of IF, a tube receiver can have low amplitude while having tens of volts. I'm really looking forward to the next part, the timebase problem sounds very interesting to dig into.

[@MagicGumable]

Always nice to see your progress

[@UsagiElectric]

Thanks!

[@ryanb8302]

Crazy that this testing gear is still perfectly useful today.

[@UsagiElectric]

The old HP 150A has been an absolutely brilliant scope! I actually use it more than the modern Siglent scope we have. Really, the only time I pull out the Siglent is when I need the ability to capture a waveform (or I need to use the scope in a place where I can put 40 kg of HP scope, haha).

[@LeonirZimmermann]

Yeahhhh, thanks by sharing this work too!

[@UsagiElectric]

Thanks for checking the video out!

[@InssiAjaton]

My early suspicion was that the mounting hardware for at leas one of the original capacitors could act as a shield. The replacement one seemed to just hang in the middle air. Then there is the story about the "ground"end of the capacitors, including film types. I have known this issue for decades, but you might check Mr Carlson's Lab for a demonstration of the effects of wrong polarity mounting. Or the effect of a shield clip. Otherwise, as an old fan of HP instruments, I am waiting for more videos of those.

[@TinyMaths]

Just discovered your channel, and scrolling through your video thumbnails I thought of two other guys I watch, CuriousMarc and HAINBACH; Funny seeing one of them comment on your video. Anyway, I have almost zero understanding of electronics, but it's still a fascination to watch you go into detail.

[@baseomatic]

Sweet!! finally getting caught up on your videos thank you! Still would love to buy some tube buffers for input from sound processor maybe even a pre amp!!! Built or a kit

[@UsagiElectric]

Thanks! Tube audio projects are something I definitely want to get more into this year. I think once I get a better handle on how to build some of the essential building blocks for a synthesizer using vacuum tubes at low voltage, that'll make for some interesting videos!

[@baseomatic]

@@UsagiElectric absolutely! I will be waiting impatiently lol haha thanks again can't wait fornthe next video

[@frankowalker4662]

Slowly but surely, it's comming together. :)

[@UsagiElectric]

Yup! Slowly working on that goal of an entirely vacuum tube based test gear setup!

[@frankowalker4662]

@@UsagiElectric Pure heaven. :)

[@taniallen5413]

Enjoyed your videos, very informative. I am presently working on a HP 521 and cannot find a manual online. I have the one for the decade counters. Where did you find the manual you were using in the videos? Thank you.

[@crasbee]

It's astonishing that the neon bulbs show such bad corrosion and nothing else does. But maybe the glitch we hunted in Discord was a bad connection on the tube or something as well due to corrosion.

[@UsagiElectric]

It has to be something to do with what the legs of the neons were either built from or coated with (or not coated with), because as you noticed they were horrendous but nothing else was quite that bad. I'm also still not convinced that my weird counting issue isn't also due to janky neons. I don't think the neons have a direct impact on the flip flop circuit, but they do essentially work as voltage reference tubes when conducting, so HP may have designed around that, and the poor or bad connections are causing things to fall out of balance. Fortunately, all the issues seem to be concentrated in the Decade Counter units themselves, which are easy to get out and work on!

[@stphinkle]

At time 17:02, I wanted to make sure you are careful around Deer. Deer in several states were found to be carrying the COVID-19 virus.

[@ropersonline]

13:54: Did you ever chase down that artefact?

[@GHILLIESARCADEANDMORE]

16:42 COOL

[@UsagiElectric]

It's always fun to see deer close up!

[@SeanBZA]

Shoot, got a whole pack of those neon lamps as well.

[@UsagiElectric]

Interestingly, the NE-2 has changed a bit over the years. The modern NE-2s you often find on eBay wouldn't actually work in this application because their striking voltage is about 10V higher and they have a narrower maintaining voltage. If the NE-2 is just being used a simple indicator, it's usually fine, but HP is using differential voltages here to either strike or extinguish the bulb, so a modern NE-2 would require a huge amount of resistor tuning to get work. Fortunately, I had a whole bunch of the older type I salvaged years ago that I've been hanging on to. Being a pack rat sometimes pays off!

[@SeanBZA]

@@UsagiElectric Got a pack of 100 of NOS from around the 1970's......

[@ldandco]

I am subscribing oh wait ! I was already subscribed

[@UsagiElectric]

Thank you so much!

[@edgeeffect]

It's such a shame that recapping is often a necessity.... modern caps just don't look as "nice" as the oldies they replace. Diode Gone Wild did a neat trick with some bad electrolytics once where he hid the replacements inside the cans of the originals. It's pity that it's not really possible to do that with "solid stripey" caps. I suppose it could be done with some artistic epoxy molding and a super skilled paint job.... but that's well into the realms of "too complicated".

[@djfaber]

Videos are great, and I'm learning a ton about EE with these, but one question, -- quiet ? Quietly? Quite?

[@mmmlinux]

Typo in the script the AI voice synthesis was working from. Almost got me, But not this time Skynet.

[@UsagiElectric]

Sometimes you grow up saying things the wrong way and no one corrects you, then all of a sudden, you're in your mid-20s and you say "quite" and your buddy goes "dude, it's pronounced 'kwite'," and you know what, you're right... but the neural pathways are already formed and I ain't chan... Sorry, I'll try to work on my pronunciation! 😆

[@UsagiElectric]

@@mmmlinux Thank you for the feedback, the previous scriptwriter has been... dealt with. Regards, Skyn... I mean Usagi Electric.

[@djfaber]

@@UsagiElectric I understand that, my five year old has picked up "buh but why" and we're working with him now to correct it. Have you tried the rubber-band on the wrist trick yet? =)

[@c1ph3rpunk]

My ex went for years saying “minus well” ‘til one day I finally had to say “that’s pronounced might as well”. By that point I think it was all but impossible to change, decades of saying it one way.

[@VandalIO]

This might be a stupid question , but How do you use oscilloscope on main earth referenced circuit without blowing it up ?

[@teslakovalaborator]

By using isolation transformer to power the measured circuit, then you can attach ground to anywhere you want. Or if the measured circuit ground is connected to earth, then you can measure it also with both earths connected together.

[@UsagiElectric]

Teslakova answered it better than I can! But, as i understand it, both the 150A and 521A in this instance are isolated from mains through the power transformer. Granted, they both share a common ground through the earth pin, but there's no path for an HV line from one to make it's way into the other since the only common point is earth.

[@DAVIDGREGORYKERR]

Could you not have used Wires Adhesive to put the wire back rather than replacing the neon.

[@UsagiElectric]

Potentially, but the wires were so corroded it actually receded back into the glass on some of the neons. Fortunately, I had a bunch of the right kind of neons already that I had been hanging on to for years that I was excited to finally be able to use!

[@arthurjean-luc8040]

super travail

[@UsagiElectric]

Merci!

[@tracyleewilliamson4727]

Cool

[@UsagiElectric]

Thank you!

[@maebeans]

wawawa

[@UsagiElectric]

Wawawa indeed!