Electronics

Quick fix: KTE-LCD-3 electric bike controller

Introduction Yesterday my neighbour came in asking to take a look at his electric folding bike. It had been beaten up during transport in his van and the controller on the steering wheel no longer responded to the power button. He had taken it to two different bike mechanics, but both of them weren’t interested. The brand was unknown to them (and likely to just about everyone) and, most often, they don’t really care much for electronics in general. Figuring out which modules to replace (much less actually attempting to repair them) most often is not within the scope of what they do. It didn’t help that he had no idea where the bike was originally purchased (it was inherited from some family member long ago), or how old it was. An electrician at his job had measured voltage up to the controller and “everything was working as it should”.

Sunday, July 6, 2025 | 4 minutes Read

Repairing a "for parts" Canon 7D Mark II.

Update (06/11/2025): I found out that “**names_are_hard**” is the lead developer behind Magic Lantern, added that information in-line. Also fixed a typo. Introduction I was recently looking for a replacement for my ageing (ancient?) entry level Canon 600D. I came across a cheap 7D Mark II body (7d2 from now on) that was sold as “broken, for parts only”. This repair was a fun and rewarding experience requiring no spare parts.

Tuesday, March 4, 2025 | 10 minutes Read

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

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

Unilumin Upad 2.6mm led screen repair

Introduction I regularly repair tiles of Unilumin 2.6mm Upad that have broken pixels. Since the pixel pitch (distance between the center of the pixels) is only 2.6mm, that leaves only about 0.5mm between the pixels. Not enough for soldering with conventional means. To do this, you do require good eyes or magnification as well as an hot air station. 96x96 pixels on a 25x25cm tile Damage by ripped off pixels. Note the distance between the center of the pixels is only 2.6mm. Pixel dimensions are 2.1x2.1mm.

Unilumin-led

Wednesday, December 22, 2021 | 2 minutes Read

HP 8640B Part 1: initial state

Introduction I recently acquired a HP 8640B signal generator. A quick summary of the specs shows why this is an interesting piece of equipment: 500kHz to 512 MHz (option 2 adds a doubler, extending the range to 1.024 GHz) Available power range is -145dBm to +19 dBm, within +0.5dB across the full frequency range Extremely low phase noise (less then -130 dBc at 450 MHz, 20kHz from the carrier) Fine tuning (when in locked mode): >+/-20ppm Integrated counter, switchable between the internal generator and an external input FM and AM modulation Beautifully engineered (but that’s just an opinion) The retail price in the mid seventies was around 12.000 USD (which in 2017 would be about 90.000 USD).

Saturday, June 10, 2017 | 3 minutes Read

HP 8711(A): modifications, tweaks, refurbishing

Introduction I recently acquired a fairly well preserved HP 8711A network analyser. As sold, this is an economy model, offering only scalar measurements, although vector information can be acquired through the HP-IB bus. What makes this unit interesting, is that the hardware is the same as the never released 8712A, which has vector capabilities. Some changes in the bootrom allow the user to “convert” the unit, making it behave like a full fledged VNA.

Monday, November 14, 2016 | 4 minutes Read

Wireless Tally for JVC GY-HM790 cameras: Part 1

Introduction I’ve been working on my wireless tally system for a while now. Apart from the connection to the camera (for which I want to use a different connector to alter the appearance of the camera as little as possible) it is finally finished. Looking back, this has taken me much more time than I expected. But as this was the first project that I wanted to do in a more professional way instead of just throwing something together that shouldn’t necessarily be a bad sign. I’ve tried to keep revisions of the schematics, board design and code, as well as a clear BOM that can be used as a guideline in the future, should the need arise.

Monday, March 31, 2014 | 6 minutes Read

Wireless Tally for JVC GY-HM790 cameras: Part 2

After lots of troubleshooting my wireless tally project/product is nearly finished. The prototypes have been tested in the field and proven to work as expected. Next up are the finishing touches: etching the boards with the final adjustments, populating them, programming the microcontrollers and fitting everything in the enclosures. An early prototype boards: An early version of the transmitter board. As a size reference: the top left pads are for a micro usb connector.

Tuesday, February 18, 2014 | 1 minute Read

Wireless Tally for JVC GY-HM790 cameras: Part 3

Part number confusion As I am currently working on a project that involves XBee modules for wireless data transmission I had to look for the best type of module. There are a dazzling amount of different versions and plenty of websites that explain the the different lines of modules (Series 1, Series2, Pro vs normal versions,…). It was much harder to match the version and antenna type that I needed with the corresponding part number, and that is what I needed to order the correct one from suppliers such as Element14 and Mouser.

Monday, September 9, 2013 | 2 minutes Read

Panasonic PT-AE100E lamp power supply repair

Introduction I was asked if I could repair a “broken” Panasonic LCD projector. The lamp would start up, flicker for a couple of minutes and then shut down. No error messages where displayed. Light! But only for about a minute or two… The owner had send it to Panasonic to have it repaired but was told that the LPS (lamp power supply) board needed to be replaced, at a cost of €450. As that was too much compared to the price of a similar new projector the owner didn’t want to invest in a repair and decided to give up on the idea of having it repaired.

Wednesday, June 12, 2013 | 2 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