PSR-E353 disassembly and key rubber contact repair

[pjd]

Hi --

I was looking for a different sort of teardown video, but I came across this video in which a tech disassembles a PSR-E353 and repairs (cleans) a key contact. It might helps someone out with a dirty key contact.

https://www.youtube.com/watch?v=DHjtvpi3vJg

The video shows you what's inside of a PSR-E353, too. As you might imagine for a low-cost, entry model, the internals are relatively simple (fast to assemble in manufacturing).

All the best -- pj

[vbdx66]

Hi pj

Nice find.

I suppose the green rubbers are what makes the PSR E353 and similar keyboards touch sensitive? It certainly looks very fragile.

Best Regards,

Vinciane.

[SeaGtGruff]

I think velocity sensitivity (or touch sensitivity as some companies call it) is achieved by having at least two sensors, or else a sensor that can detect when a key passes at least two points or positions as it's being depressed. (Honestly, I don't really know the details of how it works.) The keyboard then takes the amount of time that elapsed between when the key passed point A and when it passed point B, and uses that time (or "velocity") to determine how loudly to play the note.

There are also some keyboards that use a "tri-sensor" approach, measuring the time from point A to point B, and then from point B to point C, which allows even greater nuances of control-- for instance, maybe the performer presses the key so lightly that it goes from point A to point B, but never reaches point C, or takes longer to go from point B to point C, etc., so the keyboard is able to detect these situations and play the note accordingly.

[pjd]

Hi Vinciane --

I was all set to write an explanation and then I found this page:

http://www.openmusiclabs.com/learning/digital/input-matrix-scanning/keyboard/index.html

If you have one of the Exxx service manuals, please take a look at the "MK" circuit board layouts and the "MK" electrical schematic. In the video, the ziggy-zaggy lines under a rubber contact point are the switch terminals. The conductive material in the rubber contacts establish a closed circuit for each of the two switches under each key. As explained in the article, the different physical height of the two contacts means that the circuits are closed at different times when struck, depending on how hard the key is struck. The microcomputer (SWL01U) measures the time and converts it to MIDI velocity. (Thanks, Michael, for your explanation.)

Hope this info helps -- pj

[vbdx66]

Hi Michael and PJ,

Thanks for this very thorough explanation. This mechanism is very cleverly designed.

I am now wondering whether really cheap keyboard such as the PSR E2xx are not touch sensitive to further reduce costs, or rather simply because commercially speaking, it is more coherent to have a non touch sensitive keyboard at the bottom of the range.

Best Regards,

Vinciane.

[pjd]

Hello Vinciane --

Just took a look at the PSR-E233 manual out of curiosity. Wow, Yamaha does just about everything they can to take cost out of the E2xx models. Only one memory device -- a 4MByte PROM. No touch sensitivity means one switch contact per key, eliminating 50% of the switching diodes. Makes the E453 look like a Genos. 

-- pj

[vbdx66]

Hello Vinciane --

Just took a look at the PSR-E233 manual out of curiosity. Wow, Yamaha does just about everything they can to take cost out of the E2xx models. Only one memory device -- a 4MByte PROM. No touch sensitivity means one switch contact per key, eliminating 50% of the switching diodes. Makes the E453 look like a Genos. 

-- pj

    

I am wondering how much Yamaha is sparing by using only one switch contact per key. I strongly suspect that even more than cutting on the costs, they want their (young) customers to upgrade to a better keyboard as soon as possible. Nobody can play the PSR E263 more than a couple of Months IMHO.

I simply hate the idea of a keyboard with non-sensitive keys, even for a small kid. I think it might just discourage the young players from persevering with music learning. The PSR E363 costs about 50 € more than the E263 - the price of two music lessons. I believe the PSR E363 is a no-brainer for the parents of any music-oriented kid.

Regards,

Vinciane.

[AnupamEnosh]

E2xx keyboards and lower end models from Yamaha like F51, are toys. If a keyboard cannot serve as a good stage instrument, it is no more than a toy. I still remember how difficult it was for me, to move from playing a non-velocity responsive KB for years, to a velocity resp. KB all of a sudden. In our country, Yamaha keyboards are slightly overpriced, when compared to their offerings. So E263 costs more than a budget smartphone sold here.
P.S. : No intention to divert the topic of this thread. 

[SeaGtGruff]

I'm going to use the abbreviation "VS" for "velocity-sensitive."

I suspect that Yamaha does want a non-VS keyboard at the lowest end of their models, and they have a number of other such models besides the PSR-E2xx, such as the PSR-F51 and various local models-- most of which haven't been updated in a while.

I agree that these models are little more than toys, but the later PSR-E2xx at least had the potential to be used as inexpensive XGlite sound modules before Yamaha removed all MIDI and USB connectivity. But even without MIDI, a non-VS keyboard has the potential to be used to play voices for instruments which are traditionally non-VS, such as harpsichord and organ. In fact, I think the earliest synths probably had non-VS keyboards.

[vbdx66]

@Anupam : yes, I agree with you, these keyboards are nothing more than toys. As for the PSR-F51, I don't even understand why Yamaha is producing it.

@Michael : yes, the PSR E2xx keyboards were interesting as MIDI sound modules as long as they had MIDI connectivity. And yes, the first synthesisers didn't have touch sensivity. But I doubt that the PSR-F51 and E263 have the same sound quality as early analogue synths.

If you go on Yamaha's website and listen to the sound and style examples both for the PSR E263 and E363, apart from the touch sensitivity, it is clear that the PSR E363 also has a much better sound quality (even though it isn't a Genos of course  )

Here is the link:

https://usa.yamaha.com/products/musical_instruments/keyboards/portable_keyboards/index.html

Regards,

Vinciane.

[pjd]

Hi --

There must be sales channels and customers or Yamaha simply wouldn't manufacture these ultra low-end keyboards. Looking at the E263 and F51, they want to attract those parents who just want to buy an inexpensive keyboard for a young kid who might walk away from the whole thing in a few weeks. With respect to sales channels, they are targeted for "big box" stores (like Walmart), not music shops. A lot of these keyboards show up at yard sales (AKA "boot sales").

I'm getting ready to pass my E443 on to the next generation (my nephew's son). He'll have a good time of it and hopefully will leave his Dad's S80 alone. 

Have a good weekend! -- pj