This time I’m turning up the RAM Floppy card for the Z80 system, which turned out to be a bit more difficult than I expected. The primary gotcha was that I was using the RAF113.COM test utility to test the card and it kept throwing errors. Working through the tests with the oscilloscope it soon became clear that the card wasn’t being selected when the CPU was performing IO reads & writes, despite the source code for the utility confirming the card was addressed correctly (port A0). …and it was physically jumpered correctly, to the address in the source code. ...

A while back I found this Trio DL703 multimeter in eWaste so I grabbed it. It wasn’t working properly, so I set about fixing it.

Started digging into the broken BBC Master 128 I have. Previously I’d replaced a failed Video ULA, which at least got the right clock signals in the right places. This time around I observed that the /IRQ input pin was stuck low on the CPU - ie, an interrupt was being generated. That signal appears on the 6850 (IC45 pin 7), the user 6522 VIA (IC6 pin21), the system 6522 VIA (IC8 pin 21), and the custom memory controller IC (IC20 pin 29). ...

The new NTSC VIC arrived - let’s see if it fixes the issue, or I’ve made an expensive mistake!

A quick update on where the Vic-20 repair is up to.

In this video I take a look at a Vic-20 I brought back from the USA on a recent trip.

Edit: I’ve since bought Davinci Resolve Studio and it mostly just works. It doesn’t like the audio track on video recorded on my GoPro, but I’ve not looked into why. I may be able to fix it on the GoPro, but I record audio separately anyway. Well, that was disapointing! Growing tired of Windows and Microsoft’s shenannigans I figured I’d install Linux on another one of my machines. I do all sorts of things on this particular machine, and one of those things is that I sometimes edit videos with Davinci Resolve. Most of my video editing is done on a much beefier machine downstairs, but the projects are kept in a Postgres database and the media on a NAS, so I can edit from any machine on the network. ...

Recently I built up a little Raspberry Pi 4B to use while I travel. I use it for: Travel router: Built in wifi for my laptop and phone to connect to; An external USB WiFi dongle for connection to Hotel WiFi; A USB ethernet to connect to Hotel internet if wired is available; The built in ethernet for connecting to network equipment I’m working with; A 4 port USB serial adapter to provide serial console access into equipment; This lets me use my laptop with Hotel internet without exposing my laptop directly to it :-) It also lets me talk to network equipment, either via ethernet or serial over WiFi. ...

This time we’re constructing the PiDP 11.

This one is a bit different. My Dad dropped this by and asked if I could work out what it was. Being new year time, I was still in bed and missed talking to him so I had no background information to work with.

In this video I’m preparing the Raspberry Pi for the PiDP11 project. I’m doing this up-front so I can use it to test the hardware build during construction.

In this video I take a look at the Acorn Electron, and more specifically the ULA. It’s the heart of the system and creates one major difference from the BBC machines the Electron is derived from. A few references: Stardot - https://stardot.org.uk ULA schematic thread - Electron ULA Schematics - stardot.org.uk FPGA ULA project - Electron FPGA - stardot.org.uk

Some new equipment has arrived for the workshop, primarily to let me make better video content. First up is some truss clamps (pictured with some custom machined light spigots) that will allow me to attach lights to the new truss tube I’m about to suspend from the ceiling. I’m also hoping to hang a camera from this too - just need to come up with some sort of flexible arm I can mount it so I can rapidly position it as required. ...

In a previous video I repaired a Logitech G413 keyboard. After that video went live a viewer asked about the weight of the keyboard and suggested a video on the weight removal process. So, here it is :-)

This time around I’m building a Colour Maximite computer kit, originally bought from Altronics and dating back to 2012. I bought it on eBay for no other reason than I thought it’d be fun to build :-) The design originated with Geoff Graham and published in the Silicon Chip magazine in September/October 2012. Geoff’s own documentation on the project is at https://geoffg.net/OriginalColourMaximite.html

This time around I’m replacing the innards of this old Commodore 64 power supply. I’m not entire sure if this is one of the “PSU’s of death” that are so common, but let’s rejig it just in case. It’s derived from a reference design I found online, but in the end I was missing one crucial piece - see how many of you pick the obvious mistake before I do :-) ...

In this video I revisit the Spectravideo SVI-328’s 80 column card, after the false start we had last time (where we ended up fixing the Super Expander instead). I also look at whether we can teach the old dog a new trick (new for the SVI, not new for the 6845 CRTC) :-)

Finally! The little Apple IIc monitor is back together! All 9 inches of it!

In video #22 a month or two back I built a Tauntek logic IC tester. These are firmware upgradable, and while there were no new features in the latest release that I felt a burning desire to have, I thought I’d run through the process of doing the firmware upgrade so we could see how it’s done.

When I got my Spectravideo SVI-328, it came with a floppy drive but no floppy discs. A chance visit to the Spectravideo Facebook group for a different matter led me to a cassette file that I could use to create a disc BASIC boot disc (and CP/M boot disc). This video runs through the process of creating the disc BASIC disc using a SVI-CAS digital playback and recording device (the process to make a CP/M boot disc is almost identical). ...

Well, that didn’t go as planned… The “plan” was to test out the SVI-806 80 column video card.

This week I’m repairing a Sony TC-K590 tape deck. I started this a few weeks back but had to wait for parts to arrive from the UK. Was difficult to cut down 3-4 hours of footage into a watchable video without it ending up all disjointed – hopefully it came up OK :-)

Experimenting with desoldering techniques in this video – hoping to solicit some feedback on how to do it better and more consistently!

This time around I’m building a Tauntek Logic IC tester, which should be useful for testing 74 series logic IC’s I reclaim from old equipment, and also some 4000 series IC’s. There are other testers out there, like the Retro Chip Tester Pro (which is good for testing RAM/ROM in particular), and in time I’ll probably acquire & build one of those too :-)