[Noel] was in possession of two non-working Sinclair QLs and made a series of videos about his attempts to repair and restore them. If you don’t remember the QL, it was a computer by the famous Clive Sinclair and while it was ahead of its time in some ways, it didn’t become as ubiquitous as some of its siblings or the IBM PC. It did, however, develop an almost cult-like following. You can see the trilogy of videos, below.
The machine was sophisticated for its day–after all, the QL was for quantum leap. Based on a Motorola 68008 processor running at 7.5 MHz, the QL included 128 KB of RAM and could handle up to 896 KB, a respectable amount for 1984. It even had a proprietary network interface. However, it was especially well known for having a pair of microtape drives. These were nicer than cassette tapes but perhaps not as handy as floppy disks. They were, however, cheaper to put into a computer. While there was an official operating system, it wasn’t long before most QL users switched to Minerva, a better OS.
You can really see the differences in construction techniques for 1980’s consumer electronics and today. Of course, Sinclair was known to have reasonably inexpensive gear, so that contributes, too. One interesting thing about the video: [Noel] isn’t an expert on the QL so the video documents how he approached a new problem. Even if you don’t want to fix a QL, some of the process would be useful next time you are facing an unfamiliar board.
The two computers were slightly different versions. One had an unpopulated spot for an EPROM that the newer one didn’t provide. [Noel] built a simple adapter to allow an EPROM to work with either computer. Minerva’s EPROM had a diagnostic that identifies bad chips and that was very helpful with identifying the bad RAM chips. The second video covers some of the physical restorations and the third video covers the microdrives in detail. Overall, an interesting watch.
Sinclair was pretty obsessed with the microdrives, but they never really caught on. He did have a very interesting history in the electronics marketplace.
source https://hackaday.com/2020/12/07/sinclair-ql-repairs-and-restoration/