Author: Henri Keinonen

Ibanez IBZ-20 Amplifier schematics

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I got a Ibanez IBZ-20 guitar amplifier, that had some issues that needed to be fixed. All potentiometers were dead, and jacks were badly corroded, but in addition amplification was not working correctly. I could not find any schematics for this old amplifier, so I decided to reverse-engineer the whole circuit board.

Here is the schematic that I made:

IBZ-20-Schematic-BW

It turned out that problem with the amplifier was that one of the two 2SD313 power transistors was gone open. This in turn caused smaller transistors on PCB to act as power stage, and whole speaker current was passed trough small 270ohm resistor that could not handle that kind of dissipation.

Burned resistor due failed power transistor

I also decided to replace all capacitors, and removed that brown glue, which turns into corrosive and conductive mess when it ages and attracts moisture from air.

Recapped and glue removed
Bottom side of the PCB. Old hand taped layouts look kinda funky.

Serial port for Canon X-07

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Canon X-07 is great little handheld retro computer. But being Canon, nothin is standard. Canon has always insisted using weird proprietary connector for devices, and usually it is impossible to find connectors that would fit them. This is also a case with X-07. It uses weird connectors for serial- and parallel ports. They look bit like a normal D-sub connector, and D-sub connector almost fits into them, but it is not a good fit. I wanted to make new connector that matches X-07’s serial port perfectly, so I took my callipers and 3D cad and started to work. Read More …

Reverse engineering Emco CNC video controller

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During renovation of Emco Compact 5 cnc-lathe, I got my hands on scrapped electronics of original control cabinet. I saved some of the more interesting boards, like one that acts as rudimentary GPU. Whole video board was separate add-on, that contained video processor, video RAM, character-ROM and RS232 transceiver, and connected to main CPU board with large 32pin bus connector.
I took my multimeter, scope and logic analyzer, and stared to reverse engineer the mystics of this video controller.

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Swapping RJ12 to SMA

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I have old but trusty Thinkpad X200s laptop that is now retired but still occasionally used. Due being s model, it does not have build in 3G/WWAN antennas in display because there is no space for them. Independent internet connectivity is often useful, especially in places where there is no WiFi or good cell coverage.
Like many business notebooks, my Thinkpad still had 56k modem and land line RJ12 connector, which isn’t that useful in most western countries where POTS and analog modem services have long being discontinued.

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Designing and building ceiling light

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I forgot to take pictures during real cutting so this is just mock up pictureTampere Hacklab has ongoing design contest for lamps. I participated in with this Asian lantern styled lampshade.
My design points for lamp were to be able easily lasercut and construct it from plywood, and to incorporate some sci-fi themed elements. Steps for this project include CAD drawing, laser cutting and physical assembly. This design came out as easy to reproduce, inexpensive, and aesthetically pleasing. Read More …

Sunrise lamp add-on for nixie alarm clock.

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IMG_0848Finnish winter days are dark and cold. The sun rises only for short moment, and even then it is often cloudy, or the sun is so low that it can rarely be seen. A circadian clock is synchronized with daylight changes, and so without external stimulus from sunlight, my daily rhythm started to lag and spin around. Waking at morning was difficult task.

There is a ready-made solution for this, e.g. Philips does sell alarm clocks with build in wake-up lamps, that turn on at morning to artificially sync humans internal clock. Me being hacker, I had to make my own solution, as usual. Read More …

Radioactive trip

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IMG_6983I went for a radioactive hunt with my friend. Some time ago we heard a rumor, that in Paukkajanvaara there was small uranium mine and enrichment facility between 1958 and 1961. Amount of mined uranium was small, and after 60s reduced need for uranium, mine was closed and never re-opened. During closing no cleanup was made, and due 60s lower standards and general neglect whole mining site was contaminated with radioactive uranium products.

We packed our cameras and a geiger counter and started car at this cloudy sunday afternoon. Read More …