Another Productive Break

So, having a week off, I decided to move on a few projects. While not completely successful, I did make some good breakthroughs.

Leading up to the break, I started a repair on a huge old CRT TV, It’s not working… yet but I think I just need to check some things on the inside again. It’s such a heavy beast, I don’t get much time to work on it unfortunately. I did replace a rather bulgy capacitor.

Bulgy boi

I’ve also been building up the Retro Chip Tester for the Artifactory. I’m now short only some key transistors, so that’ll be pending yet another order to one of the big online component stockists.

CreatiVision / Dick Smith Wizzard

On the break, one of the things I did was test a theory I had developed, looking at the CreatiVision (CV from now on) schematic. The biggest problem with replacement controllers of the CV is that all the buttons work by shorting out 3 pins on the controller. This is difficult to simulate as double pole, single throw momentary switches are as rare as the proverbial rockinghorse drops. In my searching I was able to find exactly one switch, which wasn’t cheap, even in bulk.

I’d looked into replacement membranes, which would bypass a lot of the issues, but we needed a minimum order that was much larger than the potential number of buyers. Ah the problems of rare and obscure systems πŸ™‚

It was well known that, realistically, all switches were connected to one pin on the connector, except 2 buttons connected to a second pin. Looking at the schematic, however, I noticed that leading out of the controller, there was a diode on all the pins except the “common” pin. This suggested that I may be able to substitute a simple single pole single throw momentary switch (eg. the most common type of momentary switch out there, ranging from ultra low profile micro tactile for a fraction of a cent each across to exotic keyboard switches costing several dollars each) with a pair of diodes on the two input lines in line with the switch. The idea being that, when bridged, the signal can flow through the switch into the output line, but the diodes means the signal can’t flow backwards across the connection to register “ghost” connections on other lines.

The original sketch of my diode “fix”

I posted my theory on the appropriate forums and got some feedback from TOM, who is much more knowledgeable about these things, suggesting a Shottky diode may work better if normal diodes didn’t work.

I scrounged up some bits and pieces and built up a proto board with two buttons and some standard signal diodes. This didn’t work. Undeterred, I waited to get to the shops and tried again with Shottky diodes and… it actually worked! This changed everything. My setup was only able to press two keys, but they both worked independently. I spent several gleeful minutes typing “2”, “4” and variations (“24”, “42”, 224″, well you get the idea)

“2” “4” “2222” “4444” “2244” “2424” and so on.

Suddenly we could build keyboards with whatever buttons we wanted. I had ideas.

Currently I’ve been working on a simple schematic design, all SMD for space reasons, designed to drop in as replacements for the membranes. I’ve also worked out a design to replace the joypad part, using a thin, flexible PCB with etched on contacts that I want to try. Best of all, I can test a part before moving onto the next part. Hopefully I’ll end up with a design that can replace the innards of the entire controller.

Also, because I can, I have started designing a mechanical keyboard built around Cherry MX keys for that super deluxe typing experience.

Amiga 600

I still had a day or two spare, so I built up a PCB I’d designed, this one an Amiga MIDI board, based on the RastPort KA12.

Once I had it assembled, I needed to test it somehow, so I decided to finally bite the bullet and see if I could get my Amiga working with a CF Card as a substitute hard disk. I had a huge stack of old CF cards I’d salvaged from a variety of places. I had an IDE to CF adapter I’d purchased from AliExpress, so I thought I was ready to go.

I started working through the install process. This is one of those statements that hides a lot. Initially, I plugged in each CF card, booted an Amiga Install 3.1 disk (Thank you Cloanto, for including this with the copy of Amiga Forever I purchased off you!) and tried loading HDToolbox.

I ran an emulator to get these screenshots, but used a real CF Card for accuracy.

Once in HDToolbox, I’d highlight the CF card and click “Change Drive Type”. On the next “Set Drive Type” screen, I’d click “Define New…”

On the “Define/Edit Drive Type” screen, I’d hit the “Read Configuration” button, then “Continue” and one of two things would happen.

Yes we want to continue!

If the CF Card was an Amiga compatible one, I’d get a reading of the details of the drive.

Ah that well known drive brand “CACTUS”.

If the card wasn’t compatible I’d get an Error 7 “Not a Hard Disk”. It would go back into the stack for other uses.

Ruh Roh.

What was happening at this point is I could set up the partitions to my heart’s content, but no matter what I did, I couldn’t get the drives to be recognised on reboot. Thus, I couldn’t format them.

Partitioning

I’d made sure to set the MaxTransfer to the “magic” 0x1FE00 value required by CF Cards. Whatever I did, I couldn’t get it to work. Oddly, I was even able to install an operating system by running HDSetup. It would go through auto-partitioning and formatting the drives, but the drives wouldn’t be visible on the next reboot. Maddening!

In desperation, I even set up the CFs in WinUAE. They wouldn’t be recognised. I could see the drives in HDToolbox, but I couldn’t get them to be recognised. Trying to eliminate potential issues, I even tried the SD Adapter from my Amiga 1200… which worked.

So that eliminated the A600 itself. At this point I looked through my various parts bins and was able to jury rig a different type of CF Card reader, one designed for use in Laptops. I was able to use a 44 pin 2.0mm pitch female IDE to 40 pin 2.54mm pitch male IDE adapter that had come with my Amiga 1200 to plug into the onboard IDE port on the A600. I also needed to splice in a power supply patch as the adapter needed a floppy style Berg connector for power.

To my surprise it actually worked, and I was able to fully install Workbench. All done and dusted, right? Well, no. Turns out the whole thing was stacked too high for me to be able to close the case. Argh!

Next day I went town to Jaycar and purchased a 40 pin IDC connector and modified one of my 44 way 2.0mm IDE cables I had on hand to have the wider 40 pin 2.54mm connector on one end. I simply cut off one end of the cable then splayed out the wires and carefully crimped on the wider connection. Very proud of my work, I went to fit it, only to realise I’d made a cable with the wrong end on it. I had a female end and needed a male end. Oh well. I’m sure I’ll find a use for it.

Digging deep in my parts bins I managed to find a “solution”. One, I might add, that I’m not exactly proud of :-D.

It consisted of:

  • A short 44 pin 2.0mm pitch female to female cable plugged into…
  • A 44 pin 2.0mm pitch male to male adapter plugged into…
  • An adapter with 44 pin 2.0mm female to 40 pin 2.54mm pitch male. This is actually connected in reverse of it’s actual design. It’s designed so you can plug a 44pin HDD into a 40 pin IDE cable. This whole thing is plugged into…
  • A CF to IDE card adapter, that has a 40 pin, 2.54mm female IDE edge connector. I can only assume it’s supposed to be plugged directly into a motherboard. I can’t see how else it should be used.

Amazingly this works, and is in active use.

So ugly! Notice the spliced in power lead.

After all this? There was a mistake on the MIDI board. It was never going to work anyway.

Oh well, back to the drawing board πŸ™‚

Published by ilike8bits

I collect old computers and consoles

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