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MMT-8 keypad repair for dummies

June 13th, 2007 Andrew Martens

About two years ago, I was browsing through a nearby surplus/consignment shop, when I stumbled across a pair of classics: an Alesis MMT-8 and HR-16. I knew that these devices tended to have some reliability issues, and the LCD on the MMT-8 was a bit screwy, but I figured they could be fixed. I could have waited for the price to drop further, but at $30 (CAD) each it was already a good deal. As expected, most of the buttons barely worked and/or required a great deal of force before they would register. The EPROMs for each (but most crucially the MMT-8) also needed updating. Due to various other commitments (like planning a wedding), these two poor devices sat in a box, unused for about two years – until now.

CaiKote44Even a year ago, I was finally planning to get going on the repair.  Rumor had it that Chemtronics (CW-2610, IIRC) would do the trick, but I couldn’t find anyone in Canada who carried it – or anyone in the US who would even ship it to Canada. After a bit more searching, I came across CaiKote CK44 (made by CAIG) at a local shop, and had it shipped to my office. As usual, it sat on my bookshelf for almost a year before I brought it home and cracked open the pair of grey Alesis boxes. There’s another product out there – Rubber Keypad Renew by MG Chemicals – that sounds like it may also work. The following uses CaiKote’s product, and this is my experience with it. YMMV.

Standard safety precautions: I recommend that you perform this procedure while wearing an anti-static strap, on a proper anti-static mat, in a well-ventilated area, and you should wear gloves and goggles. Actually, I don’t recommend that you do this at all, you should have a trained professional do it for you. Insert standard legalese shrink-wrap cover-my-ass lines here. If you can’t do this without screwing up and injuring yourself, destroying whatever it is you’re fixing, or somehow burning your house down, don’t do it.  I did this in about 30 minutes with the fan on, working on the bathroom counter without any other precautions, and my brain is still working fine.

Inside the MMT-8Opening up the boxes is simple – remove the screws, and carefully lift the top half up towards you from the back of the machine. There’s a set of little hooks at the front that hold it in place – if you lift gently until the top half is at about a 45 degree angle, you should be able to lift it clear. Next, detach the ribbon cables from the PCB (that’s Printed Circuit Board, if you didn’t know) that is attached to the top lid. If you might forget, write a note about the cable routing, since Alesis didn’t use keyed headers. On the MMT-8, my cables go away from the main PCB on the bottom plastic (if you were to detach those), up from the interface PCB on the left and right sides, and towards the middle across the back of the LCD. Next, remove the screws that hold the PCB to the plastic – you can leave the LCD in place.

Dirty PCB ExampleIt should look something like this. If you look closely, you may be able to see on the keypad side of the PCB where the carbon contacts have rubbed away. Likewise you can also see the etched tracks work into the rubber pad.

At this point I decided to clean off the PCB. The Internet told me that 99% isopropyl alcohol was good for cleaning boards, so I dabbed a bit of alcohol on some cotton pads, and cleaned the board. I was hesitant to clean the rubber itself, as I thought I had heard a rumor of the alcohol causing problems there. Instead I just grabbed a spare swab and the stiff bristled brush that came with my CK-44, and gently cleaned off the little black contacts.

After opening up the small jar of CaiKote, I dabbed a swab in there (it’s quite thick, you only need a little bit), and went to work. If there was a smaller jar, I definitely should have bought it instead. What I had was overkill for the number of pads I had to repair. I didn’t even use up all of the product that was stuck to the inside of the lid of the container!

After Keypaddoing a few contacts, the method I decided on was to get a bit of product on the swab, then press it onto the keypad. Rubbing it around just gave an inconsistent finish. Don’t be too stingy, but don’t go crazy either (wow, that’s helpful advice) – just try to cover the pad with a light coat. The product will tend to ‘dome’ a bit when you apply it, but after I cured it for 14 hours the finish was quite flat. Do all the contacts, and then leave the rubber contact-side up to dry for several hours. I would suggest 12-24 hours, but you may be able to get away with less time. Reassemble everything, and cross your fingers.

Fortunately both my MMT-8 and HR-16 worked great after this. Well, they still need new EPROMs, the MMT-8 needs a new LED and LCD, and the HR-16’s volume slider is crap (but the parameter/select slider works fine), but at least the keypads are working well!

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  1. nick
    June 21st, 2007 at 04:05 | #1

    Hi I do repairs for the MMT-8, I can do you an EPROM v1.11 for £7.50 excluding postapge and packing which wont be a lot, I also can provide you with the HR-16B (bugless) EPROM for the same cost, , thanks Nick.

  2. September 15th, 2008 at 16:09 | #2

    Hello. I am new to this forum. I have a hr-16b that won’t power on with the mmt-8 sequencer power adapter. Is the power adapter different for the mmt-8 than for the hr-16b? If it is the same, does anyone know how I can fix this unit? It will not power on with themmt-8 power adapter but the mmt-8 will power on with the same adapter. The adatper states that it is the 10vold AC version by alesis. Any ideas would be appreciated.

    Thanks
    JW

  3. September 15th, 2008 at 23:35 | #3

    Hi Jeremy,

    If the power adapter is mechanically compatible (ie, it fits properly) with the HR-16B, then I would expect that the MMT-8 adapter should work. While the repair manual states that the power adapter for the HR-16/16B is 9VAC, the HR-16 I have sitting here also came with the 10VAC Alesis adapter, and works fine with it. The powersupply design is robust enough that either 9 or 10VAC should work fine. As I do not have an HR-16B to test with, I cannot unfortunately verify it.

    If the plug style is different (the 10VAC plugs are typically an Alesis “P2″ 3.5mm mono-style plug, whereas some HR-16Bs apparently came with a “P3″ barrel-style connector), then you will not be able to use the adapter – as it just won’t fit properly.

    If you are somewhat handy with troubleshooting and repairing electronics – or know someone who is – the repair manual for the HR-16/16B can be found here: http://burnkit2600.com/manuals/HR16_HR16B_D1_D2.pdf

  4. Don Smith
    December 4th, 2008 at 08:46 | #4

    Hi,

    Can you tell me where you got the Caikote44 as I also live in Canada and have been searching for a Canadian source to avoid a $8 USD item costing mega bucks coming across the border.

    Thanks
    DS

  5. December 4th, 2008 at 16:59 | #5

    @Don:

    I purchased my Caikote44 from RP Electronics. They seem to still sell it here for $14 CAD for a 2g bottle.

    http://www.rpelectronics.com/English/Content/Items/K-CK44-2G.asp

    When I purchased mine I got a 3.5g bottle (came with some little brushes and things), which was a lot more than I needed. RP doesn’t seem to have that particular size available any more, though. Their price is unfortunately more than most US suppliers, but given that it saves one from the hassle of trying to deal with having a ‘hazardous material’ shipped across the border, it was worth it!

    Alternately, you may be able to locate a “rubber keypad repair kit” product available at various other shops (RadioShack… err, The Source, rather), which may also work adequately. The Caikote44 seems to be a great product, though, and from my experience I would recommend it.

  6. Graham
    December 18th, 2008 at 19:06 | #6

    Hi Andrew,

    Just browsing and came across your site here. I’ve tried the Circuitworks keypad repair kit and it also works great. I’m on 2 MMT8 forum2 here if you are interested in mmt8 info, mods and repairs;

    http://www.mmt8.com/forum/default.asp

    and

    http://launch.groups.yahoo.com/group/MMT8/

    Cheers, graham

  7. Gunnar
    January 26th, 2009 at 06:47 | #7

    Hello! I´m going crazy soon. I have a black MMT-8 that works great except for the screen. It´s just bright yellow, no words. I have opened it up several times and tried to change the cords and even the screen. Took one from an HR-16, but no results. Still just yellow! The screen worked when I placed it in the HR-16 though… There is no way of altering the brightness of the screen on my MMT, for some reason it looks a bit different inside than the pictures I´ve seen. There is a little white potentiometer for this on the HR-16, and I know there is supposed to be one in the MMT too, but not in mine.
    What should I do??? Please help me someone.

  8. March 24th, 2010 at 10:36 | #8

    Hi my MMT 8 every thing seems to be working except the midi in I cant seem to get anything recorded but what was in it plays I don’t know any person experienced this problem the midi cables are fine

  9. Alex
    April 19th, 2011 at 14:51 | #9

    Hi, I just bought an mmt8, it powers on fine, original power supply, it powers on fine with the screen reading the typical alesis mmt8 version 1.10 message, but then it sticks to the message reading ’select song 90, no song name’, the red LED next to the song button as well as all the track button LEDs are all lit up and pressing other buttons does nothing, help! Please!

  10. BRENDA PETTY
    September 1st, 2011 at 22:18 | #10

    I purchased 2 alesis mmt8’s at different times on ebay and both arrived DOA (no paypal insurance) One device dumps data as soon as it is saved and begins flashing strange data on the screen, the other one has strange letters and numbers rapidly flashing on the screen always. Could this be a battery issue, Can you help me?

    BJ

    a href=”#comment-7″>@nick

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