Tom Verbeure

Tom Verbeure

@tomverbeure.bsky.social

Plays with FPGAs. There can never be enough LEDs. Hardware engineer at Nvidia, but my views here are my own. he/him. Also @tom_verbeure at the woolly elephant and the former bird site

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Tom Verbeure
@tomverbeure.bsky.social

This is a long shot, but I'm looking for a TDS3EM Ethernet extension card for a Tektronix TDS3000(B) series oscilloscope like the one shown. I only need it for about a few hours. If anyone in the SF Bay Area has one and willing to loan it or to allow me do my thing at their place, let me know!

Tom Verbeure reposted

Sam Rose
@samwho.dev

I'm writing about self-hosting and got wondering why ports <1024 are privileged on Linux, and require you to be root to bind to them. Found this explanation and couldn't help but laugh. I'd always thought it was a bit of a hack. utcc.utoronto.ca/~cks/space/b...

Tom Verbeure reposted

Tod Kurt (todbot)
@todbot.com

Want easy capsense touchpad buttons? Just a PCB & 4 resistors. Coming soon to my Tindie store! If you want to make your own, files are here: github.com/todbot/touch... This demo in CircuitPython but also works in Arduino w/ my TouchyTouch lib #circuitpython #capsense #captouch #raspberrypipico

Tom Verbeure reposted

Elise Cutts
@elisecutts.bsky.social

Cecilia Payne-Gaposchkin ✨ figured out what stars are made of ✨ when she was just 25. 🔭🧪 Her PhD thesis basically established the Harvard astro department — at a time when Harvard didn't officially allow woman students. I wrote this little profile to mark the 100th anniversary of her thesis:

sciencenews.orgHow a Harvard maverick forever changed our concept of the starsAt just 25, Cecilia Payne-Gaposchkin applied quantum physics to a treasure trove of astronomical observations to show that stars are mostly hydrogen and helium.
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Tom Verbeure
@tomverbeure.bsky.social

The paper is behind a paywall. But since the suspense was killing me, I bought the paper. There it in a black an white: "[anastruct] was developed by Tom Verbeure with the aim of making structural analysis available, ..." I'm flattered! It uses [16] as reference. Let's check that out...

Tom Verbeure
@tomverbeure.bsky.social

"Application of AI for modelling and structural analysis of a parametric 2D frame with voice assistant" This has nothing to do with anastruct either. My only explanation is that the authors used AI to hallucinate a whole bunch of BS. I want my money back!

Tom Verbeure
@tomverbeure.bsky.social

The Video Timings Calculator is my most popular webpage in Google Search by far, with most of clicks coming from Taiwan. Those are engineers working on monitors, TVs, laptops etc. Traffic drops on Friday morning and ramps back up Sunday afternoon. It also drops the week of Lunar New Year.

Tom Verbeure
@tomverbeure.bsky.social

The SR620 time interval counter came to market around 1986, just before VGA was a thing. But analog oscilloscopes were everywhere, so it cleverly (ab)uses the XY mode to render images. It’s unusable on a digital scope, it’s readable on an analog one.

Tom Verbeure
@tomverbeure.bsky.social

The HP 5370A time interval counter accepts an external clock of 5 MHz or 10 MHz to create a 10 MHz reference clock. The schematic is deceptively simple, but it's really interesting and I needed a Spice simulation to understand the basics: it's a cascade of 2 injection-locked oscillators (ILO).

Tom Verbeure
@tomverbeure.bsky.social

The HP 5370A time interval counter accepts an external clock of 5 MHz or 10 MHz to create a 10 MHz reference clock. The schematic is deceptively simple, but it's really interesting and I needed a Spice simulation to understand the basics: it's a cascade of 2 injection-locked oscillators (ILO).

Tom Verbeure
@tomverbeure.bsky.social

Each ILO consists of an LC tank with a natural resonance frequency of 10 MHz and a very low Q factor. The input signal periodically inserts a bit of energy into the LC tank and after the while it will phase lock to the input signal. The 3rd LC tank is a final 10 MHz output filter.

Tom Verbeure
@tomverbeure.bsky.social

Digikey box arrived with components for 6 different projects. What I should have done earlier is fill in the “customer reference” field for each component with the project name. Makes it so much easier to sort through the pile. This baggie has a 450V cap for my TDS 220 recap.

Tom Verbeure
@tomverbeure.bsky.social

HP 5370A repair: I had the short isolated to down to the components around 2 transistors, or so I thought. Soldered power supply and input wire for easy out of chassis debug. 
The thing works totally fine and creates a beautiful 10MHz ECL signal. Now what???

Tom Verbeure
@tomverbeure.bsky.social

The patient is reference clock buffer board A8 of the 5370A time interval counter…
It generates 10 MHz out of 5 MHz by using a very low Q factor 10MHz LC tank that syncs to the positive phase of the 5 MHz signal.

Tom Verbeure
@tomverbeure.bsky.social

There was (and is!) a short and a burnt capacitor on the clock reference board of my flea market HP 5370A counter. I was able to bypass the short with a bodge. After that, it works fine! The only thing not working yet is the circuit that was bypassed: the external reference clock input.

Tom Verbeure
@tomverbeure.bsky.social

The HP 5370A time interval counter was one of the first to use an MC6800 CPU. To make debugging easier, it has a service board that can send the MSB and LSB of the CPU address to 2 DACs, so that programming execution can be tracked on an oscilloscope in X/Y mode.

Tom Verbeure
@tomverbeure.bsky.social

This is the ancient equivalent of using a digital waveform viewer and debugging a simulation of a CPU that runs a program: by displaying the address as an analog signal, you can immediately detect execution patterns, program jumps etc.

Tom Verbeure
@tomverbeure.bsky.social

One of the flea market treasures is this heavy box that’s marked “Syntheziser”. No company or model name at all, but it must be HP, based on 1820-xxxx components inside. 5MHz in, 10 and 100 MHz out. After removing around 30 screws, you get to see this. Stunning.

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Tom Verbeure
@tomverbeure.bsky.social

The PCB has this 40MHz XTAL with heat sink that’s floating in the air, suspended by some wire and rubber bands. Or maybe it’s not a heat sink but just weight to increase mass and move vibrations to a different frequency range?

Tom Verbeure
@tomverbeure.bsky.social

One of the flea market treasures is this heavy box that’s marked “Syntheziser”. No company or model name at all, but it must be HP, based on 1820-xxxx components inside. 5MHz in, 10 and 100 MHz out. After removing around 30 screws, you get to see this. Stunning.

Tom Verbeure
@tomverbeure.bsky.social

A shiny variac, a high precision HP 5370A time counter, a back-breaking, broken (“it worked 2 months ago!”) Fluke 6071A signal generator and a nondescript 10MHz/100MHz clock synthesizer, all for $80. ‘t Was another successful Silicon Valley electronics flea market, but being there at 6am is rough.

Tom Verbeure
@tomverbeure.bsky.social

This SR620 frequency counter is my best ever electronics flea market purchase. The manual has an earliest date of 1989, my unit has 1988 components in it. 37 years old. Excellent specs: SRS still sells this model, virtually unchanged! Mine generally works fine, except when it doesn't...

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Tom Verbeure
@tomverbeure.bsky.social

Let's see if we can replace the switch? It took a while to get the switch out. (I still don't know how they were able to get it through the metal case hole!) It's an obsolete ITT Shadow NE15 TE. You can find them for $7.50 on eBay + $5 shipping. Part ordered, to be continued.

Tom Verbeure
@tomverbeure.bsky.social

This SR620 frequency counter is my best ever electronics flea market purchase. The manual has an earliest date of 1989, my unit has 1988 components in it. 37 years old. Excellent specs: SRS still sells this model, virtually unchanged! Mine generally works fine, except when it doesn't...

Tom Verbeure
@tomverbeure.bsky.social

If I'm lucky, the issue is the switch itself. It's not a real power off/on switch, but a stand-by/on switch, because part of the unit stays powered on at all times to keep the internal 10MHz oscillator stable. SRS still publishes schematics of most of their equipment.

Tom Verbeure
@tomverbeure.bsky.social

The power switch controls the control input of LM317 and LM337 voltage regulators. The red wires are for the LM317, the black wires for the LM337. Let's just solder the 2 wires together. This way, the unit is always in ON state when the power cable is plugged in...