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Viewing topic "MOX8 5 Contiguous Dead Keys"

     
Posted on: December 12, 2020 @ 04:42 AM
meryan
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Joined  12-12-2020
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I have 5 contiguous dead keys.  D-F#, The D is a ninth above middle C.
I have taken it apart and found nothing.  I swapped the rubber pad the with one from higher end.  I re-seated all the ribbon cables and multi-wire cables.  Still broke.  A while back, a note was sticking.  I remember digging inside and finding nothing.  The problem did eventually go away soon after that.  Some guy on here, a while back, had the decoder ring for the Key->matrix mapping.  Hoping someone has that info that can possibly point to a for sure lead with the info I have given.

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Posted on: December 12, 2020 @ 06:26 AM
5pinDIN
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Welcome to the forum.

Yamaha designates middle C as C3. On that basis, it appears that you’re referring to D4~F#4 (if not, please explain). If so, let us know if one key lower than D4, C#4, also exhibits the problem.

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Posted on: December 12, 2020 @ 11:37 AM
meryan
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Yes, D4-F#4.  C#4 does not exhibit the problem.  I guess you guys use 0 based indexing.. ie C0 through C7.  I do have a MOX88 btw.

Having to borrow an old Alesis 8.2 for tonight.  Not bringing it into the house as the MOX8 may get upset and possibly drop more keys....

Also, if all else fails, I am willing to purchase a MOX6 to swap parts around to find the problem if the 6 and 8s have the same boards and cable runs???

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Posted on: December 12, 2020 @ 02:27 PM
5pinDIN
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meryan - 12 December 2020 11:37 AM

Yes, D4-F#4.  C#4 does not exhibit the problem.

Interesting. I’ll get back to that further down this post.

 

meryan -

I guess you guys use 0 based indexing.. ie C0 through C7.  I do have a MOX88 btw.

Close - C0~C7 is only 85 keys (7x12 plus 1). Bottom three keys are A-1, A#-1, B-1 (the “-” = minus).

 

meryan -

Having to borrow an old Alesis 8.2 for tonight.  Not bringing it into the house as the MOX8 may get upset and possibly drop more keys....

Perhaps.  :-)

 

meryan -

Also, if all else fails, I am willing to purchase a MOX6 to swap parts around to find the problem if the 6 and 8s have the same boards and cable runs???

Many MOX6 and MOX8 boards are the same, but of course not those of the keyboard itself, which is where I suspect the problem lies based on the information you’ve provided.

Since the MOX and MOXF models are very similar in certain respects, and the 88-key models both use the GHL keyboard, having the MOXF Service Manual can be helpful. A PDF copy is available here:
https://elektrotanya.com/yamaha_moxf6_moxf8_sm.pdf/download.html

Look at the last page of the SM. Note that on the GHL88M board there’s a shared line for C#4~F#4. If that line was not getting to the processor, all six of those notes would be dead. If C#4 is working, then that line is getting to the processor. That leaves two possibilities. One is that there’s a break in that line (pc foil pattern) between C#4 and D4. The other is that the processor has developed a fault. I’m more inclined to think that there’s a foil break.

Your member profile indicates that you’re in Texas, although not the “location”. If near the Gulf or other ares where high humidity and/or “salt air” are common, sometimes pc foils open due to corrosion. Spills into the keyboard can also cause problems. On rare occasions a bug defecates and that damages a foil.

My suggestion is to look very closely at the pc foil traces. If you have access to an ohmmeter, check continuity on that line common to the six keys in the group. An area where the foil may be darkened is suspect, even if the foil appears to be otherwise intact - I’ve seen breaks hidden under the solder mask.

Good luck.

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Posted on: December 13, 2020 @ 12:01 AM
meryan
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Joined  12-12-2020
status: Newcomer

I did noticed an “oddball” rectangular area maybe 1.25"x3.8" on each of the three KB circuit boards (low/mig/high).  They had maybe 3 or 4 fatter traces tacked/solder to 6-8 square pads. The middle boards “oddball” area did not have any solder on it, but the high register card’s “oddball” area had some solder on the square pads, but it wasn’t consistent.  Kinda looked like these areas did not accomplish anything,...don’t know it the board is multi-layered.  Is this “oddball” area what you are referring to.

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Posted on: December 13, 2020 @ 04:24 AM
5pinDIN
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The boards are double-sided, no buried traces. Unfortunately the physical board diagrams in the MOXF SM PDF from elektrotanya (page 61) aren’t clear enough to guide tracing connections.

If you have the patience, I suggest that you remove keys and rubber contacts corresponding to C#4~F#4. Then use an ohmmeter to check continuity of the common connection between the pads - it’s the one at each contact area that doesn’t connect to the diodes. I suspect you’ll find that D4~F#4 are no longer connected to C#4. It then becomes a matter of tracing why.

All of this is based on C#4 working correctly while the remaining five in the group don’t.

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Posted on: December 16, 2020 @ 06:58 AM
meryan
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Joined  12-12-2020
status: Newcomer

Looks like quite a few people are monitoring this thread.  Letting everybody know I am an Elec Eng and have 2 weeks off starting next week.  I will start looking into this and report back within a week.  I don’t know who 5pinDIN is, but I have never got an expedient response that actually means anything.. EVER.. until this thread.  I literally had to change my under pants (throw them away) when I woke up the next morning and saw a meaningful response.  I am assuming they work for Yamaha, as a result, I will stick with Yamaha.  I do live east of Dallas (not real humid).

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Posted on: December 16, 2020 @ 11:46 AM
5pinDIN
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meryan - 16 December 2020 06:58 AM

Looks like quite a few people are monitoring this thread.  Letting everybody know I am an Elec Eng and have 2 weeks off starting next week.  I will start looking into this and report back within a week.  I don’t know who 5pinDIN is, but I have never got an expedient response that actually means anything.. EVER.. until this thread.  I literally had to change my under pants (throw them away) when I woke up the next morning and saw a meaningful response.  I am assuming they work for Yamaha, as a result, I will stick with Yamaha.  I do live east of Dallas (not real humid).

Thanks for getting back to us, and for the kind words. I’m just a little old retired EE who happens to have lots of electronics experience, repair and otherwise. I don’t, and never have, worked for Yamaha, although I do own several pieces of their gear and have serviced every one of them when needed. I enjoy helping people, especially those who are appreciative. Based on your earlier posts in this thread, I had a feeling that you were likely to be technically savvy.

Stick with Yamaha, or not, but whatever assistance you get here is strictly coming from a Motifator forum member. If you’d like to, say thanks to the folks who’ve made this site available.

Back to the issue at hand…
Without knowing the exact interconnections on the GLH88M board I can’t say for certain, but there might be an open via between the board sides.

Best of luck resolving the problem.

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Posted on: December 18, 2020 @ 05:30 PM
meryan
Total Posts:  5
Joined  12-12-2020
status: Newcomer

I found the problem.  As you said, there are groups (6?) of keys that share a common node (conductor) on one of the three pad conductors (middle one).  The C# - F# notes looked like they shared one.  Sure enough, the solder path was corroded open.  Because I cant see that close,,, a second check I used… I buzzed several groups of keys.  The C#4 was the only one that stood alone, indicating that its connection to any other key (specifically D-F#) was open.

Now, I need to find a 12” tall person (and an electron microscope) with a soldering iron matching their size to fix it.  I guess I can try running a bead down the trace.

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Posted on: December 19, 2020 @ 09:09 AM
5pinDIN
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The “cure” is sometimes to scrape off the solder mask beyond the break at both sides, then solder a short length of 30 gauge wire-wrap wire across the gap.

When I’m working on “microscopic” problems, I use magnification.
https://www.google.com/search?&q=visor+headband+magnifier

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