Design

Boxfish

Introduction If you need help with: Repair of electronics Design of electronic systems Software Please send me …

Tuesday, February 6, 2024 | 1 minute Read

HP 8640B Part 2: Mains input and rectifier board replacement

Introduction 6 years ago I acquired an HP 8640B that needed work (see HP 8640B Part 1: initial state). Over the last few years, I managed to clean up the unit cosmetically, but not dive in to it any deeper. Until now. I recently found some time to work on it again and started looking at the power rails. I knew that (at least) the -5.2V rail had intermittent issues, and had noticed the caps on the AC input needed to be replaced as well.

Tuesday, February 6, 2024 | 8 minutes Read

Novastar MCTRL300 basic control software

Code can be found at the Github repository. Builds/executables are not available but if anyone has use for them, I’d happily create one for you… What? Simple, basic control of brightness and test patterns/mode for the Novastar MCTRL300 (and possibly others, but I don’t have others to test). It does not allow you to configure your screen. It can be used during testing or (I can imagine) to give just this piece of software to a client to let him dim the screen when no technician is available.

Monday, February 13, 2023 | 2 minutes Read

DIY active / high impedance probe design

The “problem” I’ve been wanting to have an high-impedance (Hi-Z) probe for some time now. Up until now I’ve been searching for something like an HP 85024a which comes up on the second hand market from time to time. It would be overkill for my needs, but still nice… :) Recently I came across an old Elektor/Elektuur article from April 2004 titled “Poor man’s 1GHz active probe” by David Jewsbury. Some more research turned up the bachelor thesis of Thomas Hirschbuechler titled “Design of a low-cost 1GHz active probe”.

Wednesday, January 26, 2022 | 4 minutes Read

Dive light LED conversion

Introduction About two years ago I bought a Hartenberger “Maxi Compact” dive light for about €60. As this was a 10 year old dive light with a halogen bulb and a well-used battery pack I think that was a fair price. Anyway, the plan was to use the housing for a modded LED light. At first I just made a second battery pack, the first one was just (not) enough for one dive with the original bulb, so I needed a second one and charge one pack while diving with the other. Also bought a Graupner “Ultramat 14 Plus” battery charger as this was an affordable charger that can be used for a variety of different chemistries, but best of all, it has a port that allows for cell balancing. As I was using a 6S NiMH battery pack, that was a feature I wanted to have.

Tuesday, April 23, 2013 | 5 minutes Read