Fantastic stuff Shahriar! The pass element modification (among the other great mods) was a nice touch. Thanks for taking the time to share your projects.

Great to see some classic HP Nixie goodness on TSP and saved from the tube scavengers.

I’m really glad you didn’t butcher the counter - really neat way to demonstrate the right way to do it - and at the same time to do a repair and walk around!!

*Minor correction: The Primary PLL in the ERA Instruments EasySynth++ is actually fed from another TI PLL! This cascade has some benefits when using a combination of fractional-N and integer modes on the overall spurs. There is also a DDS in the unit as well. I will do a more thorough analysis of this instrument in a separate video where I will use a pair of them to complete my 75-110GHz network analyzer!*

I've played since I was a kid with the HP5245L my father had one in his lab in CNR in Pisa I was crazy for this instrument... You've brought my father to live and me to my childhood. Every Time it is a pleasure to listen to your lesson. Thanks !

Using a neon bulb as a form of a crude memory device is new to me and as clever as. There's so much to learn from the manuals of these classic devices. That frequency divider mod is so clean and respectful....Shahriar, you've outdone yourself in this posting. So much content in a short video. Totally enjoy it. Thanks!

That's the same counter that I used in the Air Force in the mid-1970's when I was working on FB-111A avionics. It was a part of the rack-mounted test stations. We used them when calibrating and aligning various RADAR and computer equipment components. Sweet device.

A characteristic “Shahriar” approach to responding to a request. Great work, as always.

I so enjoy this channel. Make a Nixie Tube click he says... then creates the most complicated Nixie tube clock on the planet. :)

Really cool project! I have two HP 5245L counters that I bought with the intent of doing something like this, but so far, they're just sitting in my closet. Great to see that old piece of HP gear still up and running after just replacing a few caps and one transistor!

I got a used nixi tube counter in 1979 for $50. When my wife saw it, she yelled :NIXI TUBES? She was an engineer at Fluke.

Hey, Shahriar. Yeah, these older test equipment use 1MHz as their reference input. My Marconi 2435 is no exception. It might seem hard to convert your 10MHz reference to be compatible with this, but I just use a 74LS90 to divide my rubidium standard down to 1MHz. Even the internal 10MHz reference is divided by 10 using a 74LS90. I think the whole reason they do this is that the logic chips of that time weren't very fast and CMOS chips were too expensive to use everywhere, so they convert it to 1MHz to make it cheaper, basically.

I love this, I've been planning to use casio memory 8r or similar calculator to make a vfd clock while also keeping the calculator functioning. This is definitely much cooler!

Troubleshooting these old vintage equipment (transistor level building blocks) brings so much insight - a joy to watch and learn - Thank you for sharing!

This was a great video! Seeing you not only repair, but repurpose old equipment without massive modifications is quite interesting.

Whenever I make a homebrew PCB I always add a layer of tin to the copper to increase long term durability, I noticed that otherwise the copper just oxidizes, and in extreme cases thin traces get interrupted. - maybe it would help to add some solder at least to the contact pins on your addon board - just to make sure it does not corrode over time.

The TO-220 to TO-3 conversion hack is brilliant.

Now i finally have a practical use for my old 6 digits Nixie Frequency Counter Advanced Intruments TC12 :) (a clock is perfect for only 6 digits), Thank you very nice video

One of the best videos you've done. Learned so much from this. Thank you.

By far the coolest nixie clock I've seen. Thanks for the comprehensive walk through on its functionality

An HP 5245L was my gateway drug into collecting and restoring nixie instrumentation. Great video as always, Shahriar. Good to see that Pooch is monitoring your activities and keeping you on task!

Wow, when I saw the 5245L, I had to stop, I worked as a cal tech in the Navy, and back then the Navy bought these counters by the "bushel".. We had a thing called the "octopus" and I used it to locate bad semiconductors in those decade counters... Of course we had access to the new circuit boards, and would accumulate a drawer full of failed ones, before we set about to fix them... I did not realize at the time what a fine piece of engineering this was, as was all hp test equipment, Navy later went to the AN/USM-207 more rugged mil-spec counter. I started with the HP 524B in tech school, that was all tube with a display of neon lamps that illuminated behind a stencil that had digit cutouts and did a whopping 10Mc.. Thanks for the memories. (:-)

I think its cool how you achieved that and the fact you didn't destroy the instrument to do it is awesome

Superb and I can appreciate how much work went into it.

I have one of these in my collection. Thank you for the walkthrough and some ideas for when I go through and refurbish it later! I love the modification allowing the newer cap's to fit in the same space as the old Sprague cans.

Nice adapt & overcome fix! I could watch that all day.

Neat work. A suggestion for your divide-by-10. An RS-485 Receiver will shape any 10 MHz signal of 50 mVpk-pk and higher to TTL levels. An example: MAX485 (Rx direction).

Wow, this is such a beautiful instrument. Just thinking about the effort it took to assemble one blows my mind.

The contrast in the video is funny. Old vs new. Simple idea vs overdoing it. I loved it.

Really enjoyed this one

The 5245L was no doubt state of the art for 1961, when transistors were still quite rare things, however it used conventional counter architecture, with direct counting for a fixed gate time. Only 8 years later, HP introduced the 5360A. This was truly revolutionary, it was the first reciprocal measuring counter which measured the time between zero crossings of the input signal, and then calculated the reciprocal to give the frequency. It did this with 500 TTL integrated circuits!.. If this wasn't enough, it had a time interval interpolator which provided 100ps resolution with a 10MHz clock. This performance isn't so different from the HP53132 counter from the 1990's. The 5360A is described in the HP journal from May, 1969

I have one of these laying around the shop with a few plug ins. I'm going to try to get mine running now. Thanks!

awesome stuff, what an original way to create a nixie clock

I used to repair and calibrate these counters in the US Navy more than 40yrs ago. Very nostalgic to see one again. I see several commenters below owning one. Too bad most surplus test equipment shops are gone in Southern California (maybe they could not compete with sellers on eBay, who knows).

Amazing job !

Shahriar… This was very enjoyable! Thanks so much for producing it! It should be great to see the divider schematic if you have time (no pun).

too cool, great job

Very well done.

Wow that was incredible

Excellent video Shar The performance of the HP5245L towered over its contemporaries and today its shows itself off like a fine Classic Car. I will be looking forward to a video on any plugging modules you have for it.

Great video! Nice spin on the standard clock project. Dr. Pooch is a great resource for any lab.

I've got a 5245M - when I first got it, it had been sitting in storage for something like 25 years, so I reformed all the caps using a current limited supply. I then ran through the functional test procedure in the manual, and somewhat to my amazement, it passed. In fact, the only thing that was out of spec was the main 5MHz (sorry, MC/s) xtal - and even that was OK once you figured in the drift spec over several decades. The other interesting thing was that some of the caps were well outside their tolerance - but HP obviously put enough design margin into the system that it remained in spec anyway. That old HP stuff was incredibly well made.

Air Rhodesia radio section had this counter in 1972 when I started my apprenticeship, along with HP valve signal generators. They still had them in 1980, which is why I left.

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

Great Video! I have a HP 5245M with the 5 MHz oven crystal which already accepts 5 or 10 MHz as the reference frequency. Mine hasn‘t been calibrated in around 40 years and was only around 5 Hz out.

Very clean unit!

The ERASynth is not using a DDS to generate the tunable reference for the main LMX2594/LMX2595, it is in fact using another LMX2594 for that. They run the first LMX2594 in fractional mode, leveraging the very low phase noise of this synthesizer and its 32 bit fractional divider, allowing for sub-millihertz resolution, and feed that reference to the second LMX, which runs in integer mode. So they basically run an integer-mode PLL fed by a variable reference generated via fracional PLL. The reason? Spurs! Turns out the LMX2594/LMX2595 are hard to tame beasts. They use MASH architecture with up to order 4 sigma-delta modulator, have no internal fractional dithering capability and their internal VCO bank is relatively low Q and the subbands are quite sensitive as they are relatively wideband. So in fractional mode you have fractional spurs, subfractional spurs, PFD spurs, reference leak spurs, integer boundary spurs, VCO calibration clock spurs, MASH state machine spurs and several other sources. Taming them to get around -80dBc spur performance both close-in and far off the carrier for wideband operation is a monumental task. So they optimize the first reference PLL to work well in fractional mode in the narrow operation range of 100 to 101 MHz and the output PLL works in integer mode (or maybe in fractional mode in some cases, to "scramble" away the PFD spurs when the conditions for fractional operation are best). The LMX2594/95 aren't the best synths out there working in integer mode, but to date they remain the most wideband, fundamental VCO synths out there so the tradeoff is worth it for this class of instrument.

Awesome video.

Wow, i didn't understand a lot a of the video, but it's amazing!.

What a great piece of lab gear!

you got nice gear dude , very impressed

Old school HP... Holy Phaddlediddle!

I have some HP nixie display modules which came out of a Dymec digital voltmeter from the mid-1960s. I tore it down for parts and now I have a couple drawers full of good germanium transistors.

Nice to see the Fluke frequency counter in action as thanks to the suggestion of my boyfriend I bought one.

Nice bit of kit.

At first I thought you were going to rip into the beautiful piece of equipment and convert it to a clock, thankfully I was wrong.

I respect the engineers of those times. Design and do such complex things without computers. The first space satellites were simpler)

wonderful

Great upgrade and fix. Not a microprocessor in siight. I was doing point to point wiring in 1972 when I worked at Decca Radar. I still do, but mainly for valve amplifiers and preamps. I now make my own PCBs as I'm too mean to get them done externally.

As always great video and presentation. I guess this is the first digital clock where you need to look at the LSB and see if it is stable to take a time measurement, something pretty cool I guess. ;)

You evidently belong to a younger generation than me. I fiddled with the TTL family in the good old 70ties, building such gated counters also. A single 7490 would have done the job to divide by 5 and then by 2, b.t.w. Anyhow, nice video, as always.

Well that escalated quickly, I was expecting you'd bit-bang some pulses out of an MCU not whip out an entire 20 GHz synthesizer! Absolutely love that 5245L, the immaculate physical condition is envious, no dust and no burn in, conversion was very cleanly executed.

Stunning as every time to watch his vids. And just when you thought: Oh no, he will slaughter this beautiful piece of Gear. NO he even spends the effort to enhance it’s function capability.

best nixie clock ever

I agree with the live wire proximity you highlighted - but from years of experience I can tell you that was not the norm and may be a result of previous repairs. Also the wire insulation was much tougher than the PVC from today, as evidenced by the complete lack of shrink-back on any of the connection shown. You would be lucky to strip this type of wire with snippers or cutters, you would need the correct tool for the job. EVERY solder joint would be inspected and often marked with an indelible pen or varnish to ensure there were no whiskers or solder spikes anywhere. Cable looms were laced with polyester silk to isolate sections and manage crosstalk risks. Vibration damage to insulation would be exceptionally rare to say the least, and worth a video on construction techniques of high end HP, Marconi, Wein Kerr, Techtronic type instruments over say, retail equipment.

WOW what a beauty, i actually restored one of these a coupple of month ago but mine featured the remote control and plotter outputs, those eats up a ton of space inside and it was a nightmare to work arround wire lumes... i would love to see the schematic for the divider, it will be a really nice mod since lab wide 10M reference is in my "to do on a rainy day" list. always nice to see your videos, 73 from italy!

Thanks a lot for this fine video. When I was given a 5221A 15 years ago (My first Nixie hit; quite addictive drug that) I toyed with non-destructively making it a clock too. Never got around to it, though. I later had to repair it (cooked resistors in PSU) and it still is accurate to about 0,1%; despite being steered by mains frequency only. If I may make 2 small requests; * Yes, please publish the circuit of the divide-by-ten card. * Will you pet your gorgeous cat from me, but silently so that ours does not get jealous? He's going on 16 human-years now and has a greatly increased petting need.

I recently revived a Nixie DMM from Fluke. Not because I especially need an old Fluke DMM, but so much better to see the old kit working again that for someone to buy it off me to raid the Nixies.

A quick google search found a TTL part that is a BCD or BCD-Quinary mode which is able to clock to 32 MHZ on A input and 16MHZ on the B input. The QA output in the BCD Bi-Quinary mode does have a 50% duty cycle for a single chip solution to divide by 10 with 50% duty cycle. Part is the 74LS90.

13:10 this time base is actually MUCH better than you think. - I used a 5248Lin the 1980s for several years, and it aged at 1E-9 per week, after a multi-week burn-in phase (it had been standing on a shelf for years before). Temperature influence is much below 1E-9 in a lab environment. You just have to wait - a few hours, better a full day, after short OFF periods, and 2-3 months until the crystal, which is in a special big round glass package, has recovered from a year-long OFF.

My HP 5245L needed more work: several transistors did not work. Strangely enough, the DC performance seemed fine, but not for AC. I replaced them with equivalents bought on eBay. (All germanium!) Initially, I tried some small signal silicon transistors to no avail. The ovenized timebase is actually quite good. I periodically checked it with a DCF77 disciplined oscillator and it stay spot on.

27:00 Lovely cat

Shahriar please teardown and review on HP/Agilent AC power source .

Thank you! Very nice video 😍 How can I reach you to get the schematic of the circuit?

Ohh, I love old HP tech, it's made to be serviced! And until the mid nineties the instruments came with a full service manual, including schematics and part lists IIRC. Although they often contained custom silicon, or parts with hp part numbers. Thankfully most have been documented, and sometimes it's not too hard to figure out some of their custom parts and recreate them, at least some simple ones. There are still some devices that contain a lot of unobtainium though. On the Topic of rare parts and counters: I still got a tube based counter, that uses three Phillips E1T beam deflection tubes for the milliseconds and a mechanical counter for the seconds. It has a huge 1MHz Crystal in a round metal can as its main oscillator. I'm pretty sure at least one of the E1Ts is broken though. Unlike with Nixies (which are purely used to display the numbers) these tubes actually count the pulses by integrating charge on a deflection plate and thus moving an electron beam across a screen with a scale printed on. There's basically a carry out, because the beam will hit a plate after the 10th pulse. So the counter wouldn't work, without modifying it or getting one of those stupid rare tubes. It's sad, but it's just not worth it, as it would be utterly useless as a counter.

I’ve used the 4017 counter to act as a divider, if you put the pin outputs through diodes you can tie pins together to get nice square waves of different divisions.

It is worth to mention all those discrete ECL - Emitter Coupled Logic circuits which are very fast. The schematic diagrams in 16:40 are probably simplified and do not show those high positive and negative voltages mentioned before, which serve further to accelerate transitions, either pulling up/down transistor cut-off/saturation beyond the usual +5V logic level.

Fun!

Beautiful machine. I had one until it was replaced by an HP5328 with all the options. Try a 74LS90 for the ref divider. It's a div5 followed by a div2. Job done in 1 chip.

Haha exactly the way my nixie clock works :-)

Nice, but you should design that divider with discrete transistor, to keep the nostalgia design.

6:45 Ha Ha!

You have two 5245L or just changed frequency converter from 5254c to 5264a (or vice versa)?

Did you have more than one counter? It appeared during the presentation that a second converter plug in was in place...maybe you were playing around with the different plug-ins concurrently. Great video as usual, thanks!

I have an HP 5246L (with a "Time Interval Unit Model 5262A), which looks to be a virtually identical 50MHz frequency counter, even internally. It's very nice to see it running with the nixie tube display. And, like your 5245L, it's very accurate. I was lucky when I got mine since there were no power supply issues. It's good to have seen the issue you described with the 15V rail, though, so I now know where to look first. Question: Where did you find the PDF manual for yours? I'd love to get ahold of the original manual for the 5246L

It would be neat if you could get it to sync to the USNO master clock 😁

Years ago in the 1960's my first job was electronic wireman. I did that kind of wiring all day long! It was boring as hell but paid well.

“It’s a shame it doesn’t have alphanumeric characters”. 80085 comes to mind

What brand/model USB battery pack are you using to power the synthesizer?

Ahhh yes... Another cool cat's tail. :)

I'm not sure if I dare to mention the fifty year old SN7490A, a single chip solution for the divide-by-2 plus divide-by-5 in a single package ;-)

It is a really nice counter. I have the same model but it is missing the nixie tubes and their sockets. It is on the "to fix, one day" pile. Your divide by ten circuit is quite different than what my mind went to first. I would consider a CD4017 and a SR latch, wire Out4 to set and Out9 to reset. Is it an option you considered and discarded for a reason? If so, why?

I have one of those, but it never worked. the Nixies light up, and it somewhat counts on some settings. But that was I think ten years ago, when I got it for free when some storage rooms at uni got cleared out. It has been sitting in basement since then.

At least you didn't scrap it out for Nixies, or hollow it out for a simple clock. These Nixies counter are getting hard to find now in unmucked conditon. As well I am sure this video will cause a price incraeas on any rhat are out on ebay.

35:35 - just turn it upside down and get creative! Surely the thought of having 5318008 on there has crossed your mind... now that would have to be the funniest implementation of something nixie ever!

How did you make it not count up each time when it displays the time like it did when you showed it measure 10MHz? Is there a mode to not count on screen?

6:44 😂👏

My first real counter was an HP-524C and a half rack of plug-in modules....All tubes...!!!

Hi, nice video. For a 1/10 divider you can use a 74HC4017, drive your 10Mc at the clock input and take 1Mc from the CT output.

@27:03 ROLFL!