Author Topic: AMATEURISH ELECTRONIC KEYBOARD QUESTIONS. (Read 7090 times)

230RN · « **on:** January 31, 2014, 04:09:57 PM »

I know nothing about music from the technical side, like what are minor keys and time signatures and measures and the like.

But I bought an off-brand digital keyboard on impulse yesterday at a thrift store. Was looking around for something else.

The only brand indication was "Musical Fun." It has 54 full-sized keys. I brought in the "back room" of the store and the guy back there and I tested it out. Nice action on the keys, they all worked, demo keys worked, etc. I have no idea what some of the other buttons and functions are.

With my Senior discount, it cost me $16 out the door. I realized it was more toylike than professional, but it all worked.

Get home, start playing with it, discovered that it was tuned a 12-tone note off by one note, if that makes sense. In other words, 440Hz (A4) is actually produced by the Bb (B-flat?) key.

I checked this with my frequency-meter, a microphone, and this:

http://www.youtube.com/watch?v=rFOl-9SNxLY

That link actually produces exactly 440Hz, according to my frequency-meter, at least on my laptop.

Since the rest of the keys are "relatively" correct (to my ear) to the 440Hz B-flat key, this means the actual A4 Key must really produce ~415Hz, G#.

I can't find either a manual or much of anything on that brand of keyboard, except for this image:

http://i1.ytimg.com/vi/K6G3F8_cUGA/maxresdefault.jpg

Question 1:
Are these things tunable? If so, where might you do this internally? Or does it mean somebody goofed on the wiring and wired everything one key off? (I understand, now, that somewhere in there some kind of MIDI matrix probably decodes the key presses.

)

Question 2:
There seems to be two sets of screws in the back. Two of them are in the centerline of the case, the rest are around the periphery. If I were to open it up, should I undo the two center ones first, or the outside periheral ones first? I have visions of all the keys and other parts falling out on the table if I do the wrong sequence. (I also want to put a headphone/output jack on it, which it doesn't have.) (See attachment.)

Question 3.
It came with the wall wart, and will work on the internal batteries. But the battery compartment has a screw in it and what looks like a thumb latch for opening. Removing the screw and pressing the latch in either direction does not release the cover. Any experience in this sort of thing? There's a label on the back that says "AA" cells, but the remainder of the label has been removed. Is it possible that they are actually NiCad rechargeables in there that they didn't want you to muck with, so they made this cover unremoveable? (See attachment.)

It has a serial number, but no other identifiers except the "Musical Fun" logo on the top.

I doubt that any one has direct experience with this particular keyboard, but I figured that maybe someone had enough general experience with this type or style of keyboard that you might be able to help out.

Terry, 230RN

AZRedhawk44 · « **Reply #1 on:** January 31, 2014, 04:17:36 PM »

A=440hz is not necessarily standard.

A performance group may standardize "A" anywhere from about 412hz to 450hz.

I've heard talk of some sort of Nazi Hitler conspiracy to make music more tense and rousing (nationalistic) by increasing standard A to 440 in the early 20th century (insert rolleyes here), and also heard it was pretty standard to be 412 back in Beethoven's day.

230RN · « **Reply #2 on:** January 31, 2014, 04:20:30 PM »

Yeah, I know, but I also heard that someone "standardized" it at 432 for some reason. Nevertheless, it would seem that 440 is the way to go nowadays, sorta. So I want it to be 440 if at all possible.

Quote

An orchestra tunes itself to a very particular frequency, usually 440 hertz, a note known as A 440. The note is played by the oboist, and the rest of the orchestra tunes their instruments to match it. The oboe leads the tuning because of all the instruments, it is least affected by humidity or other weather conditions.

http://www.exploratorium.edu/music/movies/tuning_hi.html

AZRedhawk44 · « **Reply #3 on:** January 31, 2014, 04:22:10 PM »

Here you go, Godwinning your thread in the first couple posts.

http://truefire.com/forum/showthread.php?10547-we-are-all-out-of-tune!!!

230RN · « **Reply #4 on:** January 31, 2014, 04:29:49 PM »

OK. Can anyone help out with the mechanics/electronics of it?

Brad Johnson · « **Reply #5 on:** January 31, 2014, 04:41:16 PM »

Some keyboards are tunable externally. Some have tuning circuits that can only be accessed by cracking the case. Some are non-tunable. Crap shoot. Sometimes you can get lucky and the mfg/model information is in the battery compartment. Short of that, opening the case may be the only way to get that kind of info.

What's in the little square just above the "Centerline Screws" label in the pic?

Also, good info here if you haven't stumbled across it already. Gives you multiple tuning options from 434 to 446 Hz.
http://www.phy.mtu.edu/~suits/notefreqs.html

Brad

geronimotwo · « **Reply #6 on:** January 31, 2014, 05:53:01 PM »

some keyboards had a little knob for tuning. others have a transpose button that allows you to push it then touch a key above or below middle c that will change the pitch. some are stuck were you get 'em. (shrug) I suppose there could be a tuning pot inside the case (enter at your own peril).

230RN · « **Reply #7 on:** February 01, 2014, 01:02:32 PM »

Well, in poking around on the net a little, I discovered that some 'boards have a "performance" button or dial, but didn't pay much attention to that. AZRedhawk mentioned: "A performance group may standardize "A" anywhere from about 412hz to 450hz," so that gave me a clue about that.

However, this particular keyboard does not have such, so I now reckon that "performance" button (or whatever) on the others had to do with external tuning.... right?

Brad Johnson asked, "What's in the little square just above the "Centerline Screws" label in the pic?"

I wondered about that myself. On close inspection it looks like it has a stud in the middle which was melted over, perhaps to "lock" the case and keeping muckers-about like me from accessing the guts. I've seen other devices which have a final access screw hidden under a label. I didn't ask about that in my initial post because I figured once I was advised as to which set of visible case screws to remove to open it, if that was indeed a welded seal, I'd know if I had to drill or grind it off to open it completely if I met resistance from that point while prying the case apart. The attachment shows this close up and personal, but badly. If it's a mangled screw covered over with magic marker, I'll have to hole-saw it away. If it's melted plastic, I'll just drill it out.

Bear in mind that I'm not looking to restore it to factory condition and returning it to a customer, so I'm not afraid of mangling things a little bit. I just want to keep it servicable, but with A4 set to 440Hz, where G-d and His Muses intended. :)

Geronimotw remarked, "I suppose there could be a tuning pot inside the case (enter at your own peril)."

Well, we'll find out. I'll only be out $16.00 "tuition," so I'm not worried about effing up a $2000 instrument. Many devices of different brands have exactly the same circuitry and chipset, they just connect or not connect various pins to activate various other options. If I can see the chip numbers, I can get data sheets on them and maybe go from there.

My main concern in opening it up is that I don't unscrew the wrong screws first and have keys 'n other entrails spilled all over the floor. Anyone have any suggestions as to whether I should undo the center screws or the peripheral screws first? The center screws are in recessed holes, so it looks like they either go through to the top cover, or an inside retaining plate that holds the keys together.

Yeah, yeah I know. Ya get what ya paid for, but as I said, I bought it on impulse 'cause I've always wanted to learn something about music.

TNX so far!

Terry, 230RN

geronimotwo · « **Reply #8 on:** February 01, 2014, 01:38:29 PM »

Quote from: 230RN on February 01, 2014, 01:02:32 PM

My main concern in opening it up is that I don't unscrew the wrong screws first and have keys 'n other entrails spilled all over the floor. Anyone have any suggestions as to whether I should undo the center screws or the peripheral screws first? The center screws are in recessed holes, so it looks like they go through to the top cover.

roland uses 4 screws at each side on the bottom, then the case opens with a hinge along the back. the screws in the middle hold the innards.

Scout26 · « **Reply #9 on:** February 01, 2014, 07:59:12 PM »

Perhaps we should start a pool as to which set of screws will give 230RN a pile of spare keyboard parts?

Azrael256 · « **Reply #10 on:** February 01, 2014, 08:41:50 PM »

Quote from: scout26 on February 01, 2014, 07:59:12 PM

Perhaps we should start a pool as to which set of screws will give 230RN a pile of spare keyboard parts?

$10 on "whichever one he touches."

230RN · « **Reply #11 on:** February 02, 2014, 08:30:57 AM »

Put me down for ten bucks on picking the correct set of screws. Optimism is the key word.

This advice looks pretty good:

Quote from: geronimotwo on February 01, 2014, 01:38:29 PM

roland uses 4 screws at each side on the bottom, then the case opens with a hinge along the back. the screws in the middle hold the innards.

I guess I'll try the extreme outside edge screws at first, and if that doesn't work, then the ones more toward the middle (on the bottom part of the picture), a little bit at a time and shaking it gently with each turn. I suspected the centerline ones would be holding down some kind of plate to hold the key "actions" down, per Geronimotw's remark.

If that doesn't give me access to the chipset (and possible internal controls) at least it will give me an idea of how it's put together and I can go from there.

If worse comes to the worst, I'll put in a headphone plug, as I wanted to do from the start, and either forget re-tuning it or design an external ring modulator to vary the pitch on an external speaker or headphones.

I want my 440 Hertz! "And by G-d," as Al Bundy would say, "these Hertz I shall have!"

Terry

geronimotwo · « **Reply #12 on:** February 02, 2014, 03:57:23 PM »

I would try the screws at the top and both sides of the photo first. the five at the bottom have a "I'm holding the keyed action together" kind of look.

Scout26 · « **Reply #13 on:** February 02, 2014, 04:34:00 PM »

Go for broke and do them all !!!

RocketMan · « **Reply #14 on:** February 03, 2014, 09:02:56 PM »

Quote from: scout26 on February 02, 2014, 04:34:00 PM

Go for broke and do them all !!!

Really go for broke and use detcord.

Harold Tuttle · « **Reply #15 on:** February 03, 2014, 09:45:51 PM »

That is a toy not a tool, I highly doubt it has a way to tune it

Harold Tuttle · « **Reply #16 on:** February 03, 2014, 09:49:26 PM »

http://www.youtube.com/watch?v=TGvcVxKpgn0

230RN · « **Reply #17 on:** February 04, 2014, 01:21:45 AM »

Wow. That vid gives me more search options: "pitch bending." And at least I know it's possible. He's probably just "rubbering" the basic clock oscillator, which means bringing the clock down only about 5.68 % for my problem. Thanks, Harold Tuttle!

You can just barely "rubber" or pull a crystal-controlled oscillator up and down that much, but I suspect the oscillator he was playing with is a free-running oscillator because of the large amount he brought it up and down. Probably a 555 timer chip rigged as an astable multivibrator*.

So now at least I know some correction is possible, and I agree with Geronimotw that "I would try the screws at the top and both sides of the photo first. the five at the bottom have a 'I'm holding the keyed action together' kind of look."

But I'm also getting the idea that those two center screws just hold the top cover on, and that if I pulled those, the top would come off and I can "inspect" my way through the rest of the disassembly without parts escaping. But I'll follow Geronimotw's advice.... Geeze, I almost typed that as "foolow."

I probably won't get to the dissection process 'til this weekend. In the meantime I'm practicing my 54321-12345 GFEDC-CDEFG fingering.

Badly. But my saluting fingers now know E all by themselves.

Mucho danke, guys!

Terry, 230RN

* Scroll to "astable":
http://en.wikipedia.org/wiki/555_timer_IC

Harold Tuttle · « **Reply #18 on:** February 04, 2014, 10:39:45 AM »

you might have more luck buying a DX7 with a couple of un sprung keys...

http://www.ebay.com/itm/YAMAHA-DX7-DIGITAL-PROGRAMABLE-SYNTHESIZER-AS-IS-/380830725307?pt=Keyboards_MIDI&hash=item58ab47b4bb

YAMAHA DX7 DIGITAL PROGRAMABLE SYNTHESIZER AS-IS. IN GOOD SHAPE POWERS UP BUT COULD NOT GET ANY SOUND FROM THE KEY AND 2 KEYS NEED TO BE FIXED

yeah, thats because this is a MIDI keyboard not an electronic piano with an built in amp and speakers...

http://www.ebay.com/itm/KORG-M1-YAMAHA-DX7-SPRINGS-RESORTES-PARA-KORG-M1-Y-YAMAHA-DX7-/221310950619?pt=LH_DefaultDomain_0&hash=item3387291cdb

http://www.ebay.com/itm/Yamaha-DX7-key-s-parting-out-fits-other-Yamaha-and-Korg-too-/161176731099?pt=LH_DefaultDomain_0&hash=item2586e1bddb

rack mount MIDI DX7 synth:
http://www.ebay.com/itm/Yamaha-TX802-Rackmount-Multitimbral-DX7-mkII-w-RAM4-Memory-Card-/221366053488?pt=Keyboards_MIDI&hash=item338a71ea70
( I bought a korg rackmount at a fleamarket for 20 bucks)

geronimotwo · « **Reply #19 on:** February 04, 2014, 11:14:46 AM »

the dx7 was the standard forever.

heck, if you want a roland digital piano i've got one on craigslist, but the shipping would kill you............

News:

Author Topic: AMATEURISH ELECTRONIC KEYBOARD QUESTIONS. (Read 7090 times)