Kids are lucky these days.  Hardware is cheap and heavily abstracted in software. USB to TTL serial about $2 AUD. A knock-off Arduino Nano for $4 AUD both with shipping included. Took about 5 mins to get a push button flashing LEDs and sending a message on serial. You can count the lines of code on two hands. Beats the hell out of writing 300 lines of assembler. (but it isn't as fun)

Tonight I fired up the high voltage power supply and had a go at getting this EM84 display tube going.

+250VDC on the anode, The grid is being operated between -20VDC and 0VDC. The heater on this tube is 6.3V.

Positive terminal on an isolated bench supply is connected to the ground of the +250V supply to give negative voltage required to drive the grid. The negative is fed into pin 1 via a 1meg resistor to ground.

As the grid voltage aproaches 0V, the shadow widens. I put up this video demonstrating adjustment of the grid.

Had a small win with some Logitec speakers today. They were exhibiting poor volume and distortion. My first guess was caps, they looked sound, but were cheap crappy caps. I re-capped it anyway, with no result. There was also a suspect SOT-23 transistor which drives the power LED, when touched, the distortion changed. I deleted the LED circuit and connected the LED with a resistor direct to the power rail. No love. Then I noticed that touching part of the board near the power switch caused the volume to increase and the distortion improve. I shorted across the power switch and the unit came to life. I didn't even suspect the power switch, it is a sealed self-contained unit which is built into the back of the volume control. So I shorted the switch with a blob of solder (no chance getting a replacement dual gang + switch unit). Now the unit works great. Just with no off =)

Fixed up a bunch of little annoying non-technical things around the house today. Tap handles, leaking toilet cistern, broken light socket and other random stuff.

I headed out to the Postgres high availabililty meetup. The meetup was really good. They went though in a lot of detail the native replication now built in (as of like 9.1 or something) to Postgres. I will be switching my postgres replication from Slonyl to native for sure.