AKA the Dick Smith Wizzard
So I recently built a replacement PSU for my CreatiVision. I have a working PSU, but it’s always best to have a spare on hand.
The original needs 9V 1A and 16V 250mA.
Thanks to some help from another collector (Hi Tim!) and some basic research, I was able to find two suitable transformers available locally.
At $13 each, the two transformers are sealed toroidals, which are quite easy to work with.
Transformer 2 (15v) (Note this is a 7.5v+7.5v transformer, but as we don’t need many amps, we can use it in series to double the volts)
(If I was going to make another batch of these, I’d probably look at making a nice PCB for them.)
Other “fixings” I purchased was an ABS “jiffy” box, a 5 pin DIN, a C14 IEC connector, A fuse holder and matching fuse, some unclad laminate, some output cable and I also used some fastenings I had laying around.
First up I designed a circuit to wire everything up to.
From here I knew what needed to be wired where.
First up I attached the DIN 5 to the end of the 4 core wire. I added heat-shrink over the end of each piece of wire, for both better mechanical stability, as well as avoiding possible shorts if something did go wrong. I also threw away the provided strain relief gland and added some double wall heat-shrink as strain relief around the end of the cable where it entered the DIN 5. Not sure I like this DIN 5 as much as the equivalent one from Jaycar, if I was being perfectly honest.
I also took a note of which colours of wire went to which pins.
I then made sure I could fit a proper strain relief gland for the main unit end, and that wasn’t too hard thankfully.
Next up was some measuring and planning of where everything was going to go. There’s not much room in this enclosure and various parts definitely wanted to “poke” in to that space, I worked out if I put the transformers to one side of the enclosure, there was enough room for the IEC connector, the fuse and the strain relief on the other side.
I used a step drill and a rotary tool to cut out holes for the IEC connector, cable gland and the fuse holder. Once they were properly prepared and measured, I was able to start wiring.
First up I made sure I had suitable spacing on the laminate board, which I did not. I ended up drilling some additional holes so the transformers could be mounted properly. I also added the holes for the transformer mounting screws and the screws to hold the laminate to the enclosure. (4 holes)
Before I mounted the transformers permanently I also used the now drilled laminate board to mark where I’d drill into the enclosure.
Finally I trimmed the laminate to size and screwed down the transformers. The transformer mounting holes weren’t tapped so I just used an M4 tap to gently add a thread to them both.
Next up I soldered the IEC connector. A short wire from Active to the fuse, and from the fuse I set a flylead to mount to the PCB later. A second flylead from neutral was also added. (This one I got wrong. I made it much too short. I ended up extending it later). I used heat-shrink liberally to make sure as much was insulated as could reasonably be done.
On the underside, using nice juicy colour coded wires, I transferred my schematic into wires on the board, making sure everything was the right length and soldered very securely in place. You want to minimise the amount of uninsulated wire here, for hopefully self evident reasons 🙂
Once that was all in and secure, I pulled the output wire through the gland, stripped a long length of the outer sheath back, and then trimmed and soldered the wires leading to the DB5, noting which wires needed to go to which colours. Don’t forget to put any mounting gear on the cable before you solder it in.
After this, I affixed the laminate board to the enclosure using nylon screws, nuts and spacers, so the whole thing is properly insulated. Note I used the lid of the enclosure as the “base” to make this easier to do.
After that it was simply a case of neatly tucking everything in, drawing some of the output cable back out through the mounting gland, locking said gland in place and then screwing the whole thing together.
Once that was done I sanity checked everything with the multimeter. There wasn’t a short between Active and Neutral. There was some resistance on each of the coils and there was no connectivity between coil pairs.
I carefully plugged it in and turned it on at the wall. No smoke. No RCD trip. So far so good.
I turned it back off and grabbed some bits-o-straw (Literally cut up bits of straw from one of those square drink boxes the kids like) and plopped them around the pins on the DIN connector so I could measure voltages.
(I also checked it against the pins on the original PSU using the same approach)
Voltages looked fine so I plugged it in and…
It works. Happy with that 🙂