From eli@gs160.sp.cs.cmu.edu Thu Nov 14 15:04:17 1996 14 Nov 96 7:13:52 EST with ESMTP; Thu, 14 Nov 1996 12:05:39 +0000 14 Nov 96 12:05:39 GMT0BST From: "Matthew S. Padden" <@pegasus.hud.ac.uk:m.s.padden@hud.ac.uk> Organization: The University of Huddersfield HEC Date: 14 Nov 1996 12:07:32 +0000 Subject: MMT8 Button repairs; concrete fix. X-mailer: Pegasus Mail/Mac v2.02 Message-ID: <453BC7E6AE1@pegasus.hud.ac.uk> Hi.. > >My MMT8 is now down for the count. I have to open it up and clean it >everytime I use it more than one day. I called allessis and they do *not* >sell the ciorcuit board anymore but they do sell the rubber pads for >around $30 or so. > >Has anyone replaced their rubber pads in the MMT8 with a new one and seen >the problem go away? Or is it a combination of the Circuit board as well? > I had this problem , along with the dreaded 'button bounce'; when you press PLAY the MMT8 will stutter terribly before getting going. I tried varuous cleaning solutions, and then got fed up with forever cleaning the board. So I added tactile switches under all the buttons to fix the problem once and for all. Here's what I did. 1. You need to buy the switches; Maplin, RS, Farnell will all do something suitable. I dod this mod a few years ago and have since sold the MMT8, so I'm afraid I can't give the part numbers. What you're looking for is a small click-action momentary switch, such as you might find in (for instance) QUAD's system remote control from their 66 range of hifi. They have a low profile body, and a peg which protrudes upward, to which you can attach keys etc. There are four pins; the switch is a DPST type. Use a meter to find which pins connect when the switch is pressed. 2. Cut off the pegs from the switches so there is just the flat switch surface. Lay the pins flat. There are some little lugs on the bottom corners of the switches; carefully remove those, making sure you don't destroy the integrity of the case. 3. Pop open the MMT8. On the underside of the button membrane, each button has either 1 (small buttons) or 3 (track and transport buttons) black conductive pads. VERY carefully slice these off to leave a smooth underside to the button. Make sure you don't puncture the membrane, as rips tend to spread rapidly. 4. Now for the tricky bit. Lay all the switches in position over the PCB 'fingers' which would normally be shorted by the conductive pads. Shape the pins so that a connecting pair lies over each side of the finger set. Cut off the two unused pins, then solder the others direct to the fingers. The switch now acts as the short between the fingers. 5. Once all the switches are in place, test fit the button board back into the casework. You will need to cut off some of the front edge of the board to make it fit (don't worry, there are no tracks down at the front edge). You'll need some slightly longer screws to hold the board and membrane in place. Tighten the screws so that no buttons are jammed down, and so that all buttons have a similar sensitivity. That's it! My unit performed faultlessly after that; all the buttons had a positive feel and NO bounce. They also worked every time. It's a bit of a fiddly job siting the switches on the board, but it's definitely worth it. I wonder if I should do the same for my Atari... Bye for now -- Matthew S. Padden Computer Music Research Group Music Dept. Huddersfield University Queensgate Huddersfield England HD1 3DH p: +44 1484 422288 x2402 f: +44 1484 472656 e: m.s.padden@hud.ac.uk From gacki@sax.sax.de Wed Nov 13 22:23:58 1996 14 Nov 96 01:23:39 +0500 14 Nov 96 01:23:00 +0500 Comments: Authenticated sender is 13 Nov 96 18:49:45 +0500 Thu, 14 Nov 96 00:45:33 +0200 Date: Thu, 14 Nov 1996 00:45:29 +0100 From: gacki@sax.sax.de (Malte Rogacki) Subject: Re: MMT8 Button repairs? anyone done this... >On Wed, 13 Nov 1996, JunoMan wrote: > >> Someone mention that you can use pencil erasers to get the conducting back. > >actually I was told by a tech that that is one of the worst things you >can do. while it does work as ashort fix sometimes, it leaves a film on the >PCboard that eventually builds up. > >I've been cleaning it with denatured alcohol and qtips. I've also used an >Xacto blade to scrape away a bit of the buildup on the rubber pads them >selves (I only did this once though). Well, I'm sort of a tech, too:-) and I'm telling you that *this* is one of the worst things you can do. Much worse than using pencil erasers. My experience with conducting rubber technology is that there actually isn't a kind of buildup on the rubber pads. The conductive surface simply wears out, it goes away finally. There's not much you can do about it. Using a blade to scrape around the surface of the rubber will definitely destroy it. Next worse thing is using alcohol to "clean" the rubber. This usually results just in a degradation of the conductive part. Anyway, the fix I've used a few times (with good results) is the following: - clean the contacts of the PCB with denaturated alcohol - get a pencil and a bit of sandpaper (or whatever it's called) - by using the pencil on the paper create a kind of graphit dust - rub the conductive rubber part in this dust This procedure has restored both switches as well as keyboard assemblies for me. It definitely lasts quite a bit; I can't say for how long, but I started using this method about a year ago, and all units still work. Malte Rogacki gacki@sax.sax.de ----------------------------------------------------------------------------- "Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you get no sound out of it." (ARP 2600 Owner's Manual) ----------------------------------------------------------------------------- Date: Fri, 3 Apr 1998 17:19:03 -0500 (EST) From: Andrew Schrock To: machines@hyperreal.org Subject: mmt-8 fix update Hi, Just wanted to make a comment on the mmt-8 fix that's on your web page... I just revamped my mmt-8 and couldn't be happier. You can get the tact switches in question from mouser. Their number is 800-MOUSER, and the part number is 612-TL1105. The mmt-8 uses a total of 43 buttons, each tact button is $.15 each at 50 pieces, so the total cost is $7.50 not including shipping for 50 pieces. Cheap! (Can you afford *not* to do this mod?) You could also try digikey, but they seemed pricier for tact buttons and they have a $10 minimum order while mouser has no minimum order. Plus, the part number I quoted above is for the perfect type of button: small, low profile, legs you can bend and clip off if needed. Total height is nonly .169 inches, and the button doesn't protrude above the top as much as some tact buttons. I was able to use the screws in the case instead of getting new ones. No more crappy membrane buttons for me.. the improvement is amazing. The mmt-8 is now a usable tool instead of a frustrating one. The mute buttons are snappy and responsive, and each button gives a satisfying "click" instead of being mooshy. take care, Andrew (aschrock@cs.brandeis.edu) Message 2/27 From David Talento Nov 29, 96 10:55:11 am -0500 Comments: Authenticated sender is Date: Fri, 29 Nov 1996 10:55:11 -0500 (EST) Cc: Electronica Subject: MMT8 Button problems - a Solution From Allesis As promised here is the final info on the MMT8 button problem. I had a *very* used keypad and was debating whether or not to tracsh the whole machine or just try and order parts from Allesis. They only sell the rubber keypad (their other option is a total overhaul of anything wrong on the unit at a flat fee of $100.) The Keypad did the trick for me. My MMT8 now works perfectly and this is with rev 1.01 ROM and a used but clean PCboard. On thing I noticed is that the new keypad has three black contacts for all of the bigger buttons (ie: start/stop/trackXX, etc) my old one only had one contact in the middle. hard to say if this makes the difference as the old one was so wore out but it is nice as a "upgrade" anyway I'm sure. So for all of you laboring with stuck button syndrome on an MMT8 this part may solve your problem. It did it for me: Part #: 9-21-1003 Name: Rubber Keypad for MMT8 Allessis : (310) 841-2272 Cost was $26.15 plus $5 shipping (UPS tracking). The part arrived in a little over a week in padded envelope. I have been using it quite a bit in the past few days to check it out and so far no problems. I am sure it will wear out in time as well (this is inevitable) but at least there is a solution that can get it up and running again inexpensively and in it's 100% original state. -------- Help Wanted Productions - Bringing you the best in organic electronic and sweaty rock music since we started. Http://www.voicenet.com/~legion Now available for SALE!: Electronic Music Project compilation cd. Over one hour of electronic music from Space to Jungle. Only $10! Message 1/27 From Robin Whittle Dec 2, 96 07:33:44 pm +0000 Comments: Authenticated sender is Comments: Authenticated sender is David Talento Date: Mon, 2 Dec 1996 19:33:44 +0000 Subject: Re: MMT8 Button problems - a Solution From Allesis Cc: Electronica Priority: normal David Talento mentioned fixing the bouncing buttons of the MMT8 sequencer, by purchasing a new rubber button panel. It is a few years since I worked on one, but here is what I remember about fixing the MMT8 and the HR16 button problem without buying any new parts. Fixing the problem is highly recommended - if you don't do it, one or both of the following will occur: 1 - It will drive you bananas and mess up your music making. 2 - The extra force that you use on the panel will tear the front panel printed circuit board from the plastic case. You will need: Philips head screw driver, isopropyl alcohol or some other solvent such as methylated spirits (don't use any other spray stuff unless you know exactly what it is and that it dries without leaving residue), a small piece of fine emery paper. The emery paper is black, waterproof carborundum abrasive paper - the sort which is as rough as the side of a matchbox, not the super fine or the coarse kind. It is years since I saw figures for the grad of this, but "400" comes to mind. Undo the screws on the bottom of the machine and gently lift the lid up. Mark all cables with indelible ink so that you know which cable goes where and in what direction. Unplug the cables from the front panel board (or leave them on the front panel and unplug them from the main PCB). Now unscrew the front panel PCB. (Are there two in the HR16?) The rubber button panel will come away from the PCB. Don't - repeat *Do Not* - apply solvent or any liquid to the black rubber conductive pads on the rubber panel. This may reduce their electrical conductivity. Use a tissue soaked in solvent to clean the interdigitated contact tracks on the PCB. I have in the past sometimes used a very light touch with the emery paper to give a fresh finish to these contacts once I have cleaned them. This may not be necessary, but I like the idea for some reason. Do it very lightly indeed - so you can just see that you have taken the shine off the contacts, and hence exposed fresh metal, without wearing them away appreciably. Now, with fresh emery paper, carefully abrade the black rubber contacts so that they no longer have a shiny surface with an impression of the contact tracks. Don't do this any more than is necessary to get a fresh, matt-black finish. Make sure, by blowing or vacuuming, that there is no rubber dust remaining. As they say in the classics "Assembly is a reversal of the disassembly procedure." Later MMT8s and HR16s did not have such trouble as the early machines - which is most of them, I think. Perhaps they changed the composition of the rubber contacts. My best guess is that some material, like a plasticiser, leaches out of the conductive rubber and leaves a coating on the metal contacts. My experience is that this operation restores excellent performance to the buttons, no matter how bad they were. I can't say how long this treatment will last, but I would not be surprised if it will give many years operation before a repeat is required. If a plasticiser was the problem, then hopefully most if it has already leached by now. Remember, don't rub too hard on those black rubber contacts! They are just a thin layer of conductive rubber. While you have it apart, you may want to remove the main board and file or ream out the holes around the MIDI sockets so you can plug connectors of any size into them. This might be a good time to check that these connectors have not become loose and fractured their solder joints - although I have never seen this happen with one of these machines. The lithium batteries in these machines are high capacity, low self-discharge units. The drain from the memory chip is usually less than 1 micro amp, so the battery has a theoretical life of 100 years or so. Check the voltage of the battery if you like - it should be 3.1 volts or above. Don't be surprised if it still has the same voltage in 20 years. I am not on the Electronica list. Denizens of that list may be interested in my Devil Fish TB-303 modifications - see my WWW site. - Robin . Robin Whittle . . http://www.ozemail.com.au/~firstpr firstpr@ozemail.com.au . . 11 Miller St. Heidelberg Heights 3081 Melbourne Australia . . Ph +61-3-9459-2889 Fax +61-3-9458-1736 . . Consumer advocacy in telecommunications, especially privacy . . . . First Principles - Research and expression - music, . . music industry, telecommunications . . human factors in technology adoption. . . . Real World Interfaces - Hardware and software, especially . . for music .