So back in May 2019 I managed to get hold of a Dragon 64 from a collector here in Sweden who was selling out his entire collection and quickly after I managed to get a Dragon 32 via eBay as well. The Dragon 32 was really what I was looking for since it was what I had as my first computer and was given to me during summer 1983 by my father. Main reason why it was a Dragon was most likely due to that the price was low due to to that they owner of the local radio store in the town was a friend of the family. The main reason to pick up the Dragon theme again was primary based on that I was reminded about this Welsh computer due to that I started to work for Cardiff based company and started to scan the internet for what was available around the Dragon.
Once I had the two above machines the first step was to check out the PSU-boards in the systems and as well since I only had one power supply, which is the same for both the Dragon 32 and 64, I needed to make sure that it was in working condition (which it was not) and as well to avoid having the PSU to burn the motherboards. So quickest and easiest things was to recap both of the PSU-boards to ensure that they where in working condition. Measuring the output from the ribbon band between the PSU-board and the motherboard showed that something wasn’t alright.
So based on what was expected as output from the PSU-board and as well having a defect power supply. Got hold of parts to build a new transformed and where I tried different casing to get something as small as possible.
Finally received the cap-kit including the new voltage regulators for both th Dragon 32 and 64 from RetroTech so this Friday evening I just had to get started to replace the caps and the voltage regulators. So far I’ve done reg and cap replacement on the Dragon PSU-boards and holding back on the motherboards. But, the LM7805 I believe wasn’t in the best shape; well at least when looking at them and by the end of the day I did get better output value from both PSU-boards for the D32/64.
Here is the snapshot of the LM7805 which I replaced on both PSU-boards:
And the final Dragon 64 work done and quickly putting together the Dragon test test whether it worked or not:
So it’s time to power on the Dragon 64 to check whether it comes alive or not to the Beetronics 17″ 4:3 screen.
What I did notice was that the Dragon 64 did had quite a bit of vertical banding lines. But, I just need to compare how much of this artifacts actually comes through when using a CRT-monitor. Assume that the Beetronics does do a certain level of enhancement of this banding issue. While some feels that the banding is part of the charm with old computer, I would say that if it can be improved I would try to fix it. So something to play around with or maybe looking into the CoCoVGA board as an easy fix.
2 February 2022 at 16:25
Very nice project. Could you please be more specific which what type of items you used for a new transformer? I see the brand new one, but where can I get one to rebuild my PSU please?
9 February 2022 at 17:56
I got the Noratel Ring Core Transformer (PN: AA-18120-TI-B) from Distrelec here in Sweden but they ship from the Netherlands worldwide. You can find more information about it from this url: https://www.distrelec.biz/en/ring-core-transformer-55va-noratel-aa-18120-ti/p/15610910.
The above tranformer was at the time the only one I could source but via the Dragon Archive forum (hardware section) you would be able to make inquiry for custom made tranformers which are a bit smaller and easier to get into a decent small case: https://archive.worldofdragon.org/phpBB3/
Additional to this, if you want to replace the PSU-board there is also the Dragon PSU replacement board which is sold by DragonPlus Electronics: https://www.dragonplus-electronics.co.uk/product/dragon-psu-board-kit-version-jan-2022/
Hope above helps.