I received a large number of new Retro USB PCBs today, which include a few small component changes from the 1.0 design. Bad news: I blundered by reversing the gate and drain connections on the MOSFETs used for level conversion. DOH!! Always read the datasheet carefully, boys and girls. On a 3-pin device, I must have assumed the gate would be the pin on the side by itself, with drain and source paired up on the other side, just like the canonical drawing of a transistor. Unfortunately that’s not true here. Hopefully I can find another brand of SOT-23 N-channel MOSFET whose pins are organized the way I thought they should be, or else this whole pile of PCBs is going into the trash. For a moment I thought maybe I could rotate the MOSFET 120 degrees, or even mount it upside down, but I don’t think any soldering tricks can save me.

After a few weeks of scarcity, more Floppy Emu hardware is again available at the BMOW store, hot off the courier truck. It’s always my goal to keep a steady inventory available, but that’s proven more difficult than I imagined. The trouble isn’t surges in demand, or assembly problems, but just managing the supplies of all the materials involved.

To sell one Floppy Emu, I obviously need to have a main board in stock. But I also need the DB19 adapter board, which is a separate part. And I need 20-pin ribbon cables. And SD memory cards. And acrylic cases from the laser cutter. And padded mailers, boxes, bubble wrap, and postage labels. Sales grind to a halt when I run short of any of those supplies. To get them at reasonable prices requires buying them in bulk, with delivery times ranging from a few days up to two months. I can’t just drop into the corner store to buy more when I run low.

Maintaining those supplies efficiently can be challenging, and it’s not something I do very well. Real companies have automated inventory management systems that automatically order more parts as needed. I just glance into a box now and then, and maybe order more supplies if the pile looks small and I’m not busy doing something else. In this case I didn’t begin the hardware assembly process soon enough to account for the long lead time. I still had lots of hardware on hand when I reordered more, but it was all gone two weeks before the order was fulfilled. It’s one more thing I need to learn to do better.