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29Apr/200

Amiga 500 – External IDE Port

After building an internal IDE port for the Amiga 500, it was time to try an external port that connects to the expansion slot. This happened to be another lesson in taking-your-time-and-doing-proper-research. As I was unpacking the bags for this unit, I realised I'd bought SMD resistors and capacitors that were, literally, microscopic. I couldn't even see them in the tape-strips that they were sent on.

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I went back to the bill of materials as linked to on the project page and realised that there was a code after the SMD items: 0805. Turns out there's an industry standard sizing and I had no idea. I therefore put in a new order to DigiKey and got these correct, got the relays correct (for another project) and then got a few other handy bits. Here's a photo of the size comparison, only take-able once I'd received the second order. Actually, I must admit that DigiKey's free shipping with any order over 50 bucks is super fast!

Now that I had the right items, I whipped out the boards that I'd had printed and started placing the chips.

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The replacement items arrived and I started assembling the boards. It wasn't until I tried to actually solder in the 74HC04 inverter that I realised I'd also ordered the wrong part. SMD chips come in a plethora of sizings, just like the resistor component sizing above and I'd purchased SOP14s instead of SOIC14s. I decided to MacGyver it and make them fit... but it caused me high levels of stress as things didn't go smoothly during the testing phase.

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After ruining around 4 boards, I managed to finally solder down the 4 ICs. This was my first attempt at SMD soldering and I must say that I'm not a fan. Firstly, I had the wrong-sized solder, but I fixed that up by purchasing the smallest available: 0.7mm. With this new solder, it was much easier to not bridge legs on the ICs, but the tip on my soldering iron was also too large. I've since ordered smaller 'blade' style tips.

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You can see above where I managed to solder the ill-fitting inverter upside down... I then tried to remove it and trashed the traces on the board. So damn fiddly... And then the resistors and capacitors... the best method I found was to tin one pad, use fine tweezers to place the component on the tinned pad and then melt it in place... from there, you can just solder up the other side. I then tested all continuity to make sure contact was correctly made.

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The edge connector wasn't a simple solder-in-position... I had options. I could solder in a right-angled header and then build a bridging board, as per the original author's instructions. Or I could use a single vertical pin header and bend the bottom row of pins of the edge connector and solder it all together. This latter option lead to a much stronger build, so I went with it.

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Finally, I just needed the IDE pin-header in place!

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After around 10 hours of debugging, I managed to get this thing to work. Firstly, one or two legs on the inverter IC weren't cleanly making contact, and then I realised I'd put the LED on the wrong way around. After a lot of further tracing with a multimeter, it turns out that my master HDD was on cable-select when it needed to be forced. I also seemed to require a second HDD as slave to get HDToolBox to read the drives correctly.

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But it works! I'll write up a post very shortly on how to work with these drives. For now, you can use the boot disks from my other internal IDE port post.

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