Wednesday, April 25, 2018

Gonna be a fun weekend

Why am I posting on a Wednesday afternoon? I got sent home from work because my allergies were making me sneeze so badly I really couldn't do much. Benadryl has calmed my sneezing, but writing this blog is about the most challenging thing I'm capable of at the moment. And that's questionable. :-)

On the bright side, this weekend is shaping up to be fun:
  • The parts I ordered from DigiKey early Monday morning arrives tomorrow via FedEx Ground.
  • The VFD power subsystem test boards I ordered last Friday from OSH Park came back from the fab yesterday (Tuesday) and delivery is promised by 8pm Friday.
  • The FPGA power subsystem test boards I ordered from OSH Park Monday just came back from the fab today (Wednesday). USPS says they'll arrive by 8pm Saturday.
The DigiKey order includes the parts for both my test boards, the transistors I intend to use to drive the printer and the keyclick transducer, and a fresh pot of solder paste. Assuming no major design changes there will still be one more order from DigiKey on this project, as I wasn't smart enough to include the Spartan 6 LX9 FPGA I'm still expecting to use and Mouser doesn't appear to be a Xilinx distributor.

Why am I buying more solder paste when I still have about a third of the tube of paste I got in 2012? This stuff was supposed to be refrigerated between uses, but apparently I forgot to put it back in the 'fridge sometime in 2013 and it's been sitting on my workbench ever since. Even refrigerated it's only warranted to be usable for 6 months, and over the last 6 years it's started to stratify in the syringe into a thick layer of solder balls topped with a layer of flux. I'd need to empty the syringe into another container to mix it, and it's nearly impossible to push out. The new pot is supposed to be temperature stable (doesn't require refrigeration) and comes in a resealable container rather than a syringe so it can be stirred.

One of the things I like about ordering from DigiKey is that they will ship via First Class US Mail for less than $6 if the order weighs less than 14 oz, and less than $4 if it weighs under 8 oz. For heavier orders, or for items like my solder paste that must ship by ground (tin/lead solder is considered a hazardous material), flat-rate ground shipping is about $9 and still arrives three days later.

What about my order from Mouser? I've started a shopping cart there with the Halo transformer for the VFD filament driver, but I haven't placed the order yet. I have a mental block on and paying $5 shipping on a $4 part (that's their least expensive shipping option), so I'm going to cannibalize my breadboarded MAX253 filament driver for its transformer. I'll place the order when I'm ready to build the final board or otherwise need a part I don't have on hand for my tests.

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