Michael Kellett's Blog

PCB micro surgery.

michaelkellett — Sun, 01 Feb 2026 12:14:02 GMT

Soldering tiny pull-up resistors to a TSSOP package. Spurred on by Jan Cumps recent (and on-going) review of the Weller Micro Soldering Kit I decided to buy some de-soldering tweezers. I used to have an Ersa soldering stati...(read more)

FNIRSI SAG-55 Hot Air Gun

michaelkellett — Thu, 10 Jul 2025 14:46:11 GMT

A few days ago genebren asked about experiences with the SAG-55 Hot Air Gun. It's quite new and looked pretty good on paper although no E14 members admitted to owning one. I've had an Atten ST862D hot air gun on my wish list f...(read more)

Two rather different communications testers.

michaelkellett — Tue, 20 May 2025 12:40:02 GMT

I spotted 2 Hewlett Packard 3784A Digital Transmission Analyzers on Ebay recently. I thought they might be interesting for the boxes but when I looked more closely I realised that they were a bit more interesting because they should be able to talk t...(read more)

RT1-M Digital Audio Analyser

michaelkellett — Tue, 06 May 2025 14:34:50 GMT

I got quite lucky (I think) at an auction a couple of weeks ago and got a lot of three Neutrik RT1-M digital audio test boxes for £99 (including commission and VAT). It's quite an old design with a slightly quirky instruction set, but very ...(read more)

Fixing an HP59313A

michaelkellett — Mon, 05 May 2025 16:41:26 GMT

I started this project a while ago (September 2024) but just picked it up again. To get the best out of this blog you will need to download the combined User and Service Manual for the HP59313A, which you can find at: https://www.keysight.com/u...(read more)

Measuring DC-DC converter Efficiency

michaelkellett — Sun, 02 Feb 2025 15:56:24 GMT

This blog is about my test rig for measuring DC-Dc converter efficiency in the range Vin/Vout 2-50V and Iin/Iout 1-10A. It can also be used to measure the power consumption of DC systems in same range. The test rig ready to run (power supply and devi...(read more)

Comparing noise from a linear PSU and an isolating USB adapter PSU

michaelkellett — Wed, 06 Nov 2024 11:38:43 GMT

Recently I blogged about a mains powered isolated dual low noise power supply I had built. scottiebabe suggested that for some purposes it would be easier and cheaper to use a USB isolator. These can be bought quite cheaply from Amazon and very...(read more)

An isolated low noise +/-5V DC power supply

michaelkellett — Sat, 02 Nov 2024 12:47:24 GMT

Introduction I’m working on test rig for accurately measuring the efficiency of DC-DC regulators or converters. It uses 2 precision current shunts to measure the input and output current. These need very low noise pre-amplifiers which must each...(read more)

Silent Switcher - LT8640s meets KiCad

michaelkellett — Mon, 30 Sep 2024 10:24:38 GMT

The first part of this project kicked off with a blog “First Design with KiCad (8.0)” about 4 weeks ago. The idea was to build a replacement for obsolete TO3 can linear voltage regulators using the Linear Technologies (now owned by Analog...(read more)

First Design with KiCad (8.0)

michaelkellett — Sun, 01 Sep 2024 14:37:57 GMT

I’ve been using the same PCB design software for over 20 years (Easy PC) and it’s served me well during that time. It’s had an update pretty much every year and it can still load files from 20 years ago. It hardly ever crashes and I...(read more)

HP 3325A Synthesizer/Function Generator

michaelkellett — Sun, 03 Mar 2024 16:18:03 GMT

I recently bought this instrument on Ebay - it's quite an old design and if you fancy one the 3325B might be a better bet since it has a much more modern processor and a few extra functions (but will cost more). It was first released in 1979, at ...(read more)

Coil Winding Machine

michaelkellett — Sat, 17 Feb 2024 17:17:36 GMT

A while ago (October) I ordered a coil winding machine from Alliexpress. It took a while to turn up (6 weeks or so) but it was free shipping. Several vendors sell the same machine with slightly different labelling and features. The prices vary ...(read more)

AD8367 as a wideband true RMS detector.

michaelkellett — Sun, 09 Jul 2023 16:05:54 GMT

In a recent thread ggabe mentioned using the AD8367 as a true RMS detector. I'd never encountered this chip before and was interested in what it could do. The official eval board from AD costs about £110 which is a little steep for a ...(read more)

A Really Simple HF True RMS detector

michaelkellett — Mon, 19 Jun 2023 16:52:15 GMT

In a recent thread Shabaz was wondering how easy it might be to make a wideband true RMS detector using a surface mount thermistor and resistor. This is a first very crude and simple experiment to find out. I soldered tiny bare wires to a 10K 0...(read more)

Time is "cheap" - 2nd user low cost precision oscillators

michaelkellett — Sun, 14 May 2023 13:34:19 GMT

Time is cheap - Investigating low cost 2nd hand oscillators from China There have been a couple of projects and discussions about time and clocks on E14 lately: Digital Clock Episode 600: Building My Dream Digital Clock: DIY 7 Segment Display wi...(read more)