Uncategorized – Ketturi electronics

Ibanez IBZ-20 Amplifier schematics

Posted on2022-07-15T13:20:30+00:002022-07-15T13:20:33+00:002 Comments

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.

Bottom side of the PCB. Old hand taped layouts look kinda funky.

Merry Christmas

Posted on2017-12-21T16:10:44+00:00Leave a comment

Ketturi electronics wishes Happy Holidays!

Reverse engineering Emco CNC video controller

Posted on2017-10-11T12:03:12+00:008 Comments

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.

Radio amateur license

Posted on2016-04-22T10:43:42+00:00Leave a comment

I got my radio amateur license and call sign OH3EYB

Radioactive trip

Posted on2015-06-01T07:08:50+00:002015-06-01T07:22:56+00:00Leave a comment

I 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 …

We made gingerbread!

Posted on2012-12-15T19:07:08+00:002015-10-21T12:05:41+00:00Leave a comment

Why u no work >:C

Posted on2012-11-05T23:09:32+00:002015-10-21T12:05:41+00:00Leave a comment

So the Nixie-clock isn’t working,.I don’t know why, but the AVR hangs when an I2C routine starts. RTC and I/O extender ic’s should be alright, because they are brand new from ESD tube. And yes, the pull-up resistors are also connected rightly and are 4,7k, which worked on the breadboard perfectly. I’m out of ideas how to make it work. My last resort is to try new AVR when it comes from ebay. If it will not work then, I don’t want to continue whole project <.<

Also, my 8800GT GPU card died today. Yes, something went horribly wrong and now it crashes every 5 minutes. Last spring I did reflow soldering because memory IC’s were detached from PCB. Maybe it’s now time to say good bye to an old friend and let it rest in peace. I will buy used 4850 for 50€ so wish me luck!

There’s something good, I found a broken and wet TravelMate 7520G 17″ laptop from the garbage one rainy day. It had broken LCD inverter cable which was an easy fix, and some coke on keyboard. I dried it, washed mobo with G20 dry cleaner (amazing stuff), changed the bios battery and it started to work \o/. Some days later i found another ACER 17″ with broken integrated GPU, which had same keyboard, so now I have a working high performance laptop (yeah I know, over 5 years old amd X2 64 TL-58, HD2400XT, 2GB PC2-6400 and 2x 160GiB WD blues is not even near high performance by todays standard(I could probably get faster netbook or tablet), but more than enough for me).