Archives October 2014

Saturday, 18th October 2014 - 20:44:25


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)

Tuesday, 14th October 2014 - 21:44:29


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.

Tuesday, 14th October 2014 - 00:18:21

Logitec LS11

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 =)

Saturday, 4th October 2014 - 18:05:45

Tim The Tool Man

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.

Wednesday, 1st October 2014 - 18:37:11

PostgreSQL Logo

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.

Daily archives