Having worked at "Santa Clara Division of HP" 40+ years ago, I love your videos. I was the service engineer for the 5334 Counter! So I literally "wrote the book" on troubleshooting that unit.

How many more years until we hear you go "I found this old NASA equipment" only for the camera to pan to show the command module shell xD

Marc, your occasional "interesting" pronunciations are part of the charm of the channel. Keep saying "aliasing" whatever way you want!

It looks like the 5257A has "ALQ-78" etched into it. That was one of the original electronic warfare receiver systems on the Navy's P-3 sub hunter aircraft. I makes me wonder if that module lived a life looking for submarines, and detecting the frequency of the radar pulses it was receiving?

Figures that HP would have used a modulo-f PLL in 1968. A good decade later, a few FM tuners used the same principle to grid-lock their primarily mechanically-tuned LOs to either 50 or 100 kHz. The point was combining the stability of a PLL tuner with the high Q of a mechanically-tuned frontend (not to mention the small pulling range kept phase noise down, a major problem in early PLL tuners that was limiting their SNR until people figured out how to make lower-noise VCOs - turns out that using a high-value resistor for varicap isolation directly adds its broadband voltage noise to the tuning voltage, modulating capacitance accordingly). Since regular tuners already tended to provide a certain amount of pulling range (courtesy of a varicap diode) for AFC, that part of the circuit would have been easily adapted, you "merely" needed the sampling and PLL bits. Frequency readout was generally provided by both a classic dial scale and a digital counter by then. See Pioneer TX-9800 and Mitsubishi DA-F20. Incidentally, grid-locking an oscillator like that goes back about another decade, with the Siemens E-311 communications receiver (introduction ca. 1960). With no varicap diodes in sight, they had to employ variable inductors (L changing with saturation governed by DC current), think magnetic amplifier technology. Very steampunk! 'scuse me if I have posted this before (I have a feeling I may), I hope I'm not sounding like a broken record... broken record... broken record... *snap* crackle* *pop* ... Anyway... I'm routinely in awe of what Silicon Valley flea markets will provide!

Marc pushes nerdiness to unprecedented levels 😆

I learned more about this old equipment from you than I ever did in school. Great work, as always.

Your videos feature some of the best mysteries I have ever listened in on. Hunting down the culprit and finding it is an amazing process. Thank you for the mind expansion!

Marc, man I love the intro music. Gets me bobbing each time!

Wake up babe! New CuriousMarc video! 😊

HP frequency counter plugin design team - a division in all but name! They came up with so many ingenious ways to measure frequencies outside the base counter frequency!

Tying to the Apollo frequency at the end was a nice touch.

In love elevator music explanation time.

And I thought I already had known all of the different frequency counting methods of HP. Great job of explaining this "new" method, with elevator music 😄. I just love your trouble finding methods. Many thanks.

Mind boggling and awesome as always. Keep it up, you curious Marc :D

Always astonishing. 👍

I just love your persistence… and always love simple solutions (extender missing wire).

Great work, as always.

Thanks for another great content.

WOW! Nice troubleshooting...

NASA is going to want all that gear back for Artemis! 😂

love your stuff, I want to be like you some day

I don't know if it was specifically these, but I remember using rack-mount components very, very much like these in undergrad physics lab courses in the 1990s. I remember once rigging up some kind of setup that was counting particles detected from some radioactive source on the Nixie tube, and just thinking "if Hugh Everett is right there's another component of the universal wavefunction that is exactly like this world except that there's a different number being shown on that Nixie tube."

I had a standalone instrument with that comb method. I've forgotten the number now but it was full-rack with Nixies like the 5245, and no plugin. It did the multiplier search on it's own, with logic. It mixed the comb with the incoming signal, obtaining one low-frequency result. It worked out which tooth of the comb was mixing by looking at how far the result shifted when the oscillator was varied : this gave the multiplier. It was a lot like the 5340A, but if I recall correctly it had a much lower direct input (12.4MHz ?) and a mixed input to 12.4 GHz.

I recently learned a new French expression which might be apt when it comes to describing the contributors to this channel: "Jusqu'au boutiste ".

Yup. Thanks from Denmark, Scandinavia. Viva, Aloha und Gesundheit.

@15:32 - "...we will have to repair this one..." Gee, what a terrible, terrible shame. Merde. 😁

Another nice restoration video. That's one more for the Houston! :) You could try a ribbon cable with IDC Centronics connectors on both side, 1:1 on all contacts.

Nice plugins. The 5257A is really neat. I've got one which works but found it very difficult to use in the "real world" - the input seems quite insensitive so driving it from a FET probe or similar to see what's going on in a circuit is more difficult than I'd like.

Marc, Time to begin design for an Earth Receive setup of Artemis II (late 2024, early 2025). Radio amateurs (1969-72) did this (S-band) with Apollo program. DIY Challenge for 55 years later.

Nice

I remember when fast counters had neon lamps in rows of 10 , each row representing a digit, and the light would raise up each digit.

Quick qustion: on the archive pictrure taken from the apollo tracking station, there are no plug-in modules in the counters. Was is enough for them without any plugin?

i actualy used all this stuff back in rbe day😂

Stumbling onto a stack of HP counter plugin modules. I have to admit that never happens to me.

23:12 right about here I was shouting: adapter pin out ???

🎉

@CuriousMarc Marc, when you find a faulty active component such as a transistor, do you check the passive circuitry around to make sure it is not another fault? Why do active components fail actually (presumably all passive ones around are ok)?

Hi there! Nice video, can be that this counter have more bandwidth than those that use a RF cavity? I don't know for what use HP produced this counter but if the oscillator that you want to sintonize it's clear is in several GHz, anything you do will change several hundreds of MHz up or down. If the cavity have very high Q it will have a very small active range and will be a very hard try to sintonize GHz the oscillator. By the way if you have some replacement transistor guide I have a JFET that I can't found any info about it. The part is 2SK206-3

kool

So? How much better is the 5255A with both diodes vs. the one with only one diode?

Being designed 10 years later, this one has ICs in it! The programmable divider clearly uses them, probably 74xx TTL? That would have been a lot of transistors when done 10 years before...

Which flea market did you get these at? Saratoga?

🇵🇱 tnx.

😎👍

Will there be more 8-inch floppy drive repairs in our future, or are those over and done with after the previous marathon batch?

✌️✌️

The Feb 1968 issue of the HP Journal has a full description of the HP5256A downconvertor and the HP5257A transfer oscillator, together with an analysis of the frequency resolution that can be achieved with each technique. Marc, I do not think you have the 5256A? Otherwise you are the King of the 5245L and modules

You're gonna need a bigger add-on collection.

HP equipment, check, complete Apollo showcase, checked. Wouldn't it be cool to install a Raspberry PI4 and an AI engine on R2-D2 and show them too? :)

Bonjour ! Savez vous parler Français ? Vous avez un accent Français. Merci pour vos vidéos très intéressantes 👍

I don’t know if I’m first or not, but do I get a prize if I am?

No audio?