I’ve made a few power supplies over the years. The first one was in 1978 or 79 when I was about 13 or 14, At that time what is now TAFE NSW (Technical and Further Education) in Australia ran short night courses for hobbyists. My mother went to quite a few including sewing, upholstery, carpentry and small motor mechanics. I’m not sure if any TAFEs run these types of courses now, but I believe in our small town they only run courses that give students industry qualifications. I can understand this change, but I still find it rather sad others are gone. I only went to one course, or at least I think it was run by TAFE. It was an electronics course. It was held in the classroom of an old private boys’ school, with its dark timber lined walls straight out of a Harry Potter scene. It was refreshing to be in a classroom learning in a practical way something I enjoyed and no assessments.
In that course we built a few simple projects. One of them was electronic bongo kit. A simple kit and one that I found disappointing. I’m interested if anyone else built it and got any enjoyment from it.
One student built a simple amplifier built around the LM380 IC and connected it to a turntable and speaker. It sounded pretty good. Some of us in the class finished the course by building a mains power supply that output 2 – 22 volts at 2 amps. It started as the Dick Smith Universal CB power supply kit (K-3448) which we then added an analogue voltmeter and variable voltage pot. We also made some tweaks to the circuit that extended the output voltage range.
It was a good project and I still use it, but it doesn’t have a current limiting feature. None I have built since have it either. It was only relatively recently that I learned the benefit of current limiting. To rectify this a few years ago I bought a 4KX buck-boost power supply module. These are cheap and I don’t believe they provide a very smooth supply, but I don’t do many projects and for most I do it should be ok.
The case
I’ve now finally put it in a case. I used an old 2 way 25 pin Parallel switch box.
I think at one time I must have had two printers, and the box was used to switch between them. It had been sitting unused in the shed for over 20 years and the case had begun to rust. They don’t appear to be very valuable, so I decided to use it. It had the benefit of only having a single hole in the front panel. After taking the cover off I was surprised to see the number of wires and soldering. I’m not sure if these were manually soldered, but if so, it must have been quite a task with 75 wires and 150 connections.
A quick build
The switch and connectors were removed and put in a parts box. There isn’t much to this build, so I’m not going into detail. Here is a photo of the insides.
Other people’s builds
There are a lot of other power supplies online using this module and you are probably best looking at those. Here is a list of some on Instructibles:
- DIY Bench Power Supply
- Laboratory Power Supply From Old ATX
- DIY Bench Variable Power Supply – ZK-4KX
- Mini Laboratory Power Supply
- USB-C Powered Bench Power Supply
How to use the module
Finding instructions on how to use the module was a bit harder than I expected. It uses combinations of short and long presses, so instructions are helpful. There wasn’t anything in the eBay listing or any other places where I found if for sale. I did find these: This instructible has a link to a this manual and this post ZK-4KX Buck-Boost Power Supply Module Documentation has a couple of links including this one that matches my module.
Power supply for the power supply
To power the module, I’ve used an old Dell laptop power supply. This came with an old broken laptop I was given. I must have had the forethought to remove the connector from the motherboard before scrapping the board. I soldered the connector onto a protoboard and mounted into the back of the case. I’ve even managed to fasten one of the bolts at a rather jaunty angle. There is room to add a different connector if I ever need to.
I painted the whole box satin black. I thought all black would look good. It’s ok, but not as good as I expected.
Completed
For now, the box is functional. I’m not sure if or what I will do to improve it. Adding smoothing may be worthwhile but I have not investigated that yet.
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This image was generated by the AI image generator built into wordpress.com. The prompt used was “Generate an image of 15 year old boys soldering electronics in a schoolroom that is in the style of a Victorian English school.” Comic book style was selected. If you manage to work out what is on the blackboards, let me know 🙂
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