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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

429 Posts416 Follower162 Folgt
Elise Cutts@elisecutts.bsky.social · 11mo ago

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:

How a Harvard maverick forever changed our concept of the stars

At just 25, Cecilia Payne-Gaposchkin applied quantum physics to a treasure trove of astronomical observations to show that stars are mostly hydrogen and helium.

sciencenews.org

Sarah Tuttle@niais.bsky.social · 11mo ago

Wait a minute. Why aren't we celebrating the hundredth anniversary of Cecilia Payne-Gaposchkin's dissertation.

Tom Verbeure@tomverbeure.bsky.social · 12mo ago

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.

Search traffic to video timings calculator. A red arrow points to the drop in traffic around Lunar New Year.
Tom Verbeure@tomverbeure.bsky.social · last yr.

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.

SR620 time interval counter with an oscilloscope on top of it. The scope shows a screen with frequency and other data. Zoomed in on the oscilloscope screen.
Tom Verbeure@tomverbeure.bsky.social · last yr.

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).

Schematic of the 5 MHz/10 MHz to 10 MHz clock circuit of the HP 5370A. 3 10 MHz LC tanks are marked in red.
Tom Verbeure@tomverbeure.bsky.social · last yr.

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.

Digikey bag. The customer reference field says “TDS 220 recap”.
Tom Verbeure@tomverbeure.bsky.social · last yr.

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???

Workbench with laptop showing a schematic, an oscilloscope showing a square waveform and a sine wave, and a PCB with probes and wires.
Tom Verbeure@tomverbeure.bsky.social · last yr.

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.

Reference frequency buffer PCB of an HP5370A. A red arrow points to a burnt capacitor.The reference frequency buffer PCB plugged into the chassis. There is a red bodge wire.The HP 5370A displaying a measured frequency of 9,999,999.9925 MHz.
Tom Verbeure@tomverbeure.bsky.social · last yr.

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.

Screenshot with the following text highlighted: "There are also two DACs for displaying the lower eight bits of the addressbus on one axis of an ordinary oscilloscope and the upper eight bits on the other axis to provide a "map" presen- tation that, to someone familiar with it, gives an instant indication of the behavior of the instrument."
Tom Verbeure@tomverbeure.bsky.social · last yr.

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.

Inside of a flea market clock synthesizer. Connectors of the synthesizer.