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Repairing a Yamaha Motif Rack Rackmount Synthesizers
Old 26th August 2016
  #1
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Repairing a Yamaha Motif Rack

This is going to be a pretty long post with lots of pictures, so I'm going to break it up into several pieces.

More than a few years ago, I bought a Yamaha Motif Rack on eBay. The description said the encoder wheel didn't work but the up/down buttons would do the same thing (albeit much more slowly,) and since the price was right ($170-ish) and I've wanted one for quite a long time, I bought it.

Well, he was definitely right -- the encoder wheel was shot. What the seller didn't mention was the the display was damaged; perhaps a fifth of the vertical lines are out when first powered up cold:
then all but 3 or 4 come on after it's warmed up:
Judging from the way the encoder wobbled in place, I figured someone must have just kicked it on the wheel.

You have to understand that this is mounted in a rack and rarely touched; programming and sound selection is done via MIDI so it wasn't a high priority to repair it immediately, but I hate broken toys. Syntaur had a new encoder wheel which I bought, but I couldn't find any information on the LCD screen, and after a while I just stopped looking. Finally, after maybe a couple of years of getting tired of looking at this cantered wheel with a couple lines out, I decided to start my search anew.

I'd posted an inquiry on the Motifator forums with no luck. Searching the web for a service manual only yielded results for the Motif Rack XS which I thought surely couldn't have the same display. So a couple weeks ago I bumped my Motifator query and one of the more prolific posters responded with the part number, which was the same as the XS (!?!). Syntaur had a new part listed for it -- brand new -- so I bought the display.
Old 26th August 2016
  #2
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So now comes the disassembly.

First, I removed the rack mounting ears, which are held by four screws each:
Next, removed the top front/top rear/side screws, and finally the four allen screws from the front, being careful to separate the different types of screws for later reassembly:
Prying the volume control was slightly more difficult than I would have thought. I had to slip a thin common screwdriver behind the knob and carefully wiggle it off.

The PLG module connectors are kept in place in the bay with nylon stays, and needed to be freed:
At this point the entire top cover slides back and off, and now I can take a look at the damage.

The screen module is held in place with only two screws, and the encoder wheel in place behind a thin plastic hood with a 1/4" thin locking nut over the threaded collar. And it's completely shot. I could see the entire encoder has been completely opened and the little board is just being held in place because of the way it's inserted into the panel rail:
To access the encoder board, I need to remove the screen. Since I'm replacing the screen anyway, I completely removed the unit and disconnected it from the push-pull pressure lock collar on the flat flexible display cable:
... which opened up some access to the encoder board.

In hindsight, I probably didn't need to do this next part, but after removing the retaining nut from the encoder board and disconnecting the 4-pin connector, I found that the board wasn't exactly going to just pop out like I thought it would.


Last edited by dluther; 26th August 2016 at 04:23 AM..
Old 26th August 2016
  #3
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So I decided I needed to remove the front panel rail. This involved removing the bottom four screws near the front in the recessed puchouts, then tilting the entire rail backward from the top and sliding it back:
With this rail removed, it was easier to coax the encoder board out of the hole. This board is tiny -- it barely fit in my PanaVise circuit board holder (I'm buying the small board holder to avoid these problems in the future...):
With the board removed, I could see the damage: completely opened, barely held by the little metal keepers. Since there are only 5 desoldering points, I decided to use my bulb desoldering iron instead of the vacuum to remove the solder from the pins, and as much as I could from the mounting tabs. I then had to coax the old encoder out with a small jewler's common screwdriver, prying underneath each side of the encoder while holding the iron on the soldered tabs to keep what was left of the solder fluid, one at a time.
At this point I had a crazy idea that I could reassemble the encoder, so I did. And it worked, somewhat:
But there was a horrible "catch" in it. Since I had the new part, I figured I was wasting time and soldered the new encoder into the board. Due to the configuration of the encoder knob, there wasn't a neat way to put this into a normal vise, so I removed the PanaVise holder arms and set them directly next to each other and gently squeezed the front of the board on the encoder to expose the three pins for soldering:
Once the three data pins were soldered, I moved the board back into the cradle, pinched the solderable mounting tabs in and soldered those into place:

Last edited by dluther; 30th August 2016 at 12:12 AM..
Old 26th August 2016
  #4
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I re-installed the encoder board and secured it with the nut and attached the connector, then connected the new display.

Now it was time to test. I connected the power supply and pressed the power switch:
Success! The display was perfect, and the encoder moved smoothly, with a nice fluid feel. But most importantly, it worked!

I unplugged the power supply and reassembled the front panel rail, secured the screen, pulled the protective plastic off the newly installed display and took that opportunity to clean the inside of the case window.

You know, just in case there was any dirt hiding there.

Since I had to remove a piece of tape holding the flat ribbon cable for the display against the inside of the front panel rail. I used some gaffer's tape to re-secure it in place:
Then I slid the top cover into place, re-installed the PLG cards and set the PLG connector cables back in their nylon stays:
Then I put all the cover screws back in, reattached the rack rails, and gave it one final check out:
Now she's back in rack #1 with some of her best friends:
Overall, the Motif Rack was surprisingly easy to work on. It would have been nice to have the actual service manual for the original Motif Rack if for nothing but the part numbers, but this was a pleasant experience without any unexpected problems, and only took a couple of hours. And most importantly a successful repair -- like she was never damaged!



Many thanks to "5PinDin" on the Motifator forums for his help identifying the screen part, and Syntaur for having brand new components in stock, with pretty fast shipping!



Last edited by dluther; 26th August 2016 at 04:33 AM..
Old 26th August 2016
  #5
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A nice rack!
Old 27th August 2016
  #6
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Quote:
Originally Posted by stevedemena View Post
A nice rack!
Thanks!

I designed and built the rack boxes myself, thinking I should make a thread about that as well -- 3 13U rack boxes out of 2 4x8 sheets of plywood...
Attached Thumbnails
Repairing a Yamaha Motif Rack-rack-3.jpg   Repairing a Yamaha Motif Rack-rack-4.jpg  
Old 27th June 2017
  #7
Hi, a bit off topic but do you find both PLG cards are slowing the Motif Rack significantly?
Thanks!
Old 28th June 2017
  #8
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Quote:
Originally Posted by kloopy View Post
Hi, a bit off topic but do you find both PLG cards are slowing the Motif Rack significantly?
Thanks!
No, not really as far as slowing down the overall Motif and its built-in features. I've noticed the PLG cards themselves are slow, which goes for the Motif Rack and my S90ES. Slow, in that it's a noticeable delay when selecting patches off any of the PLG150 cards I have (AN/DX/PF). But not in playing or response; I've many patches that are layers of the internal hardware plus a PLG patch.

This "patch select delay" does not occur at all in my MU2000EX, which I use as a PLG container. I've mentioned this on the Motifator boards, but never got a satisfactory response.

Not sure if this is helpful...
Old 30th June 2017
  #9
Lives for gear
Really good description of the process too. With lots of good pics. Nice rack.
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