I regularly play the piano for English Country Dances and Contra Dances. My main axe is a Yamaha P120, an 88-key keyboard with weighted keys. I take it to most every gig, since one never knows what kind of piano will be available at each hall. The downside is that it's 41 pounds, which is a bit heavy.
To cut down on weight, I resolved to build my own. I wanted to find a weighted keyboard mechanism that I could remove, cut down to somewhere between 64 and 73 keys, and turn into a very simple MIDI controller. Last week, I found such an item on craigslist for a mere $100 -- a Kawai CN2 Digital Piano with a bad controller board:
Upon getting it home, I discovered that the controller board wasn't dead. While there was a lot of digital hash coming out of the speakers, one could hear notes being sounded (very softly) in response to keys being played. The situation improved markedly after disabling the reverb. From this, I guessed that the problem must be located in an area of scratch RAM being used to do the reverb simulation. I opened the box in order to find out:
At first I was disappointed, because there were only two ICs on the board -- one was a Fujitsu microcontroller, and the other I assumed to be a highly-integrated ASIC containing samples, DSP, scratch RAM, and so forth. I relaxed a bit after removing the board, because it had plenty of other silicon on the reverse:
After typing in some of the part numbers into search engines, I found the RAM chip: the G-Link GLT6200L08, a 256k x 8 CMOS SRAM. After examining it under a magnifying glass and poking at it with a probe, I could see that some of the solder joints were poor. I sharpened my soldering iron (quite literally, since I don't usually work on TSOP chips), applied some flux, and heated each of the pins in turn to ensure a good joint. I plugged the board back into the chassis, fired everything up, and everything worked perfectly!
Today I brought the keyboard to the office -- I'm trying to work up some jazz tunes with my workmates so we can sit in at the local pub one evening.
Back to searching for a dead keyboard...