It's been a little while since I've actively worked on the HDD Synth. On Maslow's hierarchy of needs it's right at the tip of the pyramid, meaning life likes to kick me back down from the top more often than I'd like. 

With a very welcome Christmas break fast approaching, I'm planning to finish up the PCB design for the HDD Synth MK2 and get it sent off for manufacturing with PCBWay.

However one thing that's always troubled me about working on a hardware enhancement for retro computers is that if I make a mistake on the design it's possible it could cause damage to mine or other peoples computers.

How do I test it safely before I put it inside a computer?

By making my own simulated ISA card slot of course!

With the HDD Synth MK2 I've simplified the design so that I'm only using the +5v and GND pins on the ISA bus. Hopefully in the future I'll revisit reading HDD activity from the bus, as I really love the idea of that plug'n'play implementation

Thanks to eBay I was able to source an ISA slot which I plan to mount in a hefty piece of wood.

But how to power the ISA card slot?

With a USB C decoy board

These nifty little circuit boards take advantage of the USB C power delivery capabilities. So by changing the jumpers on the board it's possible to request power delivered in the form of either

• 5v
• 9v
• 12v 
• 15v
• 18v
• 20v

For the requirements of an ISA slot the +5v option is perfect

I'll spare you the construction pictures, as they aren't pretty - however this device only needs to be functional, rather than beautiful

Thankfully it certainly is functional as my multimeter is showing the 5 volts coming into the card as required.

Next stop, finalising the MK2 PCB design