EEV Blog: 256, Sagan's Yamaha PSR-80 digital piano potentiometer log replacement - Page 1
Forum section: electronics / general

author: Lawsen
author_rank: Frequent Contributor
timestamp: March 11, 2012, 08:37:27 pm
content: The carbon strip inside the potentiometer wears out with time as you mentioned, 25 years old. Do not forget to insert a knob in the that new pot installation in your video. The red strip on the piano keys is a damper. The keyboard is either capacitance or resistance with a scanning method, very advanced for that time 25 years ago. There are four famous brands in electronics pianos:Casio, really improved, variety of design, sizes, and sound quality from low to studio, concert quality with a one man band capability and great low pricesYamaha, sometimes not worth the price.Roland, really expensive.Korg are great and sometimes on sale.Kurzweil are expensive like the Roland.I totally like this video on how to repair an electronic music keyboard.

author: SeanB
author_rank: Super Contributor
timestamp: March 11, 2012, 08:52:45 pm
content: Yes, old school DIP packages and an embedded Z80 as well. You will probably find those IC's were made for Yamaha by Sharp, but were branded as Yamaha parts.

author: bruce273
author_rank: Contributor
timestamp: March 12, 2012, 12:26:50 am
content: http://www.flickr.com/photos/bruce273/6828088900/#in/set-72157629200345382/This keyboard I was working on had a similar design for the keys, but there was also a single strip for after touch.

author: SgtRock
author_rank: Unknown
timestamp: March 12, 2012, 02:09:25 am
content: Greetings EEVBees:--I await the music video. Sagan on keyboard, Dave on Didge."When people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together."Isaac Asimov 1920 - 1992

author: Herr R aus B
author_rank: Regular Contributor
timestamp: March 12, 2012, 05:47:59 pm
content: :-)as for your question regarding the variable resistor pad - the pressure depending resistance surely would control the aftertouch. that was introduced to give the musician an extra way of expression - for example after touch might be associated with a vibrato - the more you press, the more it vibrates :-) the velocity usually is calculated be measuring the time between the begin and the end of the key movement. means you usually have two switches - one is activated when the key starts going down or leaves a defined start position and the second is activated when the key reaches a defined end position. the shorter the measured time, the faster the key moved and the harder it was hit, resulting in an equivalent velocity value. this also might explain, why you found these three nozzlespinswhateveryoucalltheminengish with the different lenghth rsp. height :-)regardsaxelps: great blog once again :-)

author: AntiProtonBoy
author_rank: Frequent Contributor
timestamp: March 13, 2012, 02:40:26 am
content: The floating point DAC perked my interest. Presumably you can get something similar for IEEE 754 floats?

author: ToddFun
author_rank: Contributor
timestamp: March 14, 2012, 10:52:30 am
content: here is a photo of what looks like a bit of heat damage on Dave's keyboard circuit:

author: BlackHawk2399
author_rank: Newbie
timestamp: March 28, 2012, 02:37:14 pm
content: I think that the WIPER(middle pin) of the pot broke and was not being properly DRAGGED on the resistance surface.