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Thread: Need info on opening up an Ensoniq ZR-76

  1. #1
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    Need info on opening up an Ensoniq ZR-76

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    Hi, Has anyone ever had to open up a ZR-76?

    I just recently bought one which is in beautiful cosmetic condition but does have 3 keys which sit lower than normal. When I opened the expansion board cover, one of the weights was visible so I pulled it out and saw that the plastic had broken. I can hear something else moving about inside and suspect it might be another couple of weights.

    My problem is that I can't figure out how to open up the case to remove them. I even tried to take off one of the end caps by removing the 3 screws on the underside, nearest the edge but it doesn't want to come off.

    I'd appreciate it if someone could give me some hints as to the correct procedure to get inside this. Should I be trying to lift the top cover off (after removing the knobs and certain screws) or should I be trying to do everything with it upside down?

    Normally, I would not have any problem as I have reasonable experience of dismantling various electronics, etc. but I don't want to ruin this keyboard by trying brute force.

    Thanks in advance for any help you can give,

    Al

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    I'm having the same problem!

    This happens when the key weights break. I'm irritated because I had one fixed some years ago and the guy who did it showed me how to get the action out. Now I need to open it up again and I can't seem to remember! I can tell you this much:

    If you turn the thing over, you can remove the row of screws nearest the front of the board (the ones in the indented slot). That releases the action, and you will be able to rock it back and forth a bit. If my memory is correct, there are only a few more screws to remove and the whole top panel should come up (I think some of the buttons might come with it...). Anyway, I think the whole action lifts up out of the front. Sorry I can't be more specific.

    I also remember something about not removing certain screws that hold some of the electronics in place (I think they were the smaller sized ones on the back of the board).

    Please let me know if you've had any luck with this; thanks!

    Allan

  3. #3
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    Opening a ZR 76

    Hi,

    It's been some time since I last worked on this but I finally managed to get the key assembly removed, although i'm not sure that I did it the quickest way. I removed all the screws on the underside which allowed me to take off the bottom panel. I then photographed every area of the internals so that I would have a reference if any problems arise when rebuilding.

    I disconnected the circuit boards and removed them which then allowed me to remove the keyboard assembly. On first inspection, it looked like the keys were secured by the long thin rod which runs the full length of all the keys and acts as a pivot. However, I soon realized that this is not the case. To remove the keys, all you do is remove the rear spring, gently push in on the plastic tab near the end of the key and lift it out while sliding it towards the front. Incidentally, it is not necessary to remove any black keys to access the hammer weights but to remove the complete section of weights (of which there are two on the ZR76), all the small self-tapping screws on the back of the frame must be taken out. The weight assembly can then be carefully slid out.

    My main problem now is carrying out actual repairs to the weights. Five of them have broken off due to brittle plastic and some others look rather fragile so if anyone has successfully repaired damaged weights, I would really appreciate any advice you can give me. My first thought is to try repairing the plastic with superglue but I'm not sure if that's the best solution.

    Anyway, I hope this helps someone to at least get to the stage where they can see what needs to be fixed on their Ensoniq.

  4. #4
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    Gourockian, you rock! Your post helped me immensely.
    I purchased an Ensoniq ZR-76 keyboard new in 1999. I have loved it, even though it is a bit heavy to lug around. Lately it had developed two problems - a key clack on 19 of the 76 keys, spread throughout the keyboard, and an irritating tendency to randomly re-select the sound I wanted, in the middle of a song. I had considered taking it to someone to repair (I live in central Jersey) but thought I would take a look and see what was going on myself, first: I suspected both problems were physical, rather than electronic, in nature. The key clack came when the key was released, which meant that it was the weight dropping down on its base and hitting something. The sound selector parameter knob was suspiciously wobbly, and I suspected either it had gone bad or had unseated itself and was making erratic contacts, resulting in random sound changes.
    Taking off the back cover: Rest the keyboard upside down on its end edges on a couple of short 2x4s or something similar to keep the face from contacting your work table. The selector pots are very fragile and you need to avoid putting pressure on them as they are attached directly to one of the printed circuit boards inside. You need to remove all of the screws along the back lip EXCEPT the 4 small ones along the plug-in slots; they hold the plug-in board in place; don't remove them until you get the back cover off. You do not have to remove the 6 screws holding the access panel, either, as the panel will come off with the back. You do have to remove all of the other screws on the underside EXCEPT those in the slot. The slot screws hold the key action assembly in place (along with a few others on the back panel) and you don't want to drop it until you can see what you are doing. As you remove the screws, pay attention: some are longer than others, and a few are pointed; you do want to remember which ones go where. I drew a diagram of the back cover and noted which screws went where.
    With the back cover off, I also photographed in closeups the open innards of the keyboard. A great suggestion. Every time I removed something, I re-photographed that area. I also made note of which screws go where inside.
    Make a diagram of which of the connector cables connect to which board and where. This helps immensely if you have to disconnect stuff, when it comes time to plug it all back together.
    To remove the key assembly you will have to remove the two brackets (a small cross-type bracket on the high note end, and a larger box-like bracket at the other end. There are a couple of signal connectors attached to the keyboard assembly micro-boards; unplug them carefully. Also unplug the wheel sensor plugs on the little circuit board that the key pressure sensor tapes are also plugged into. Be careful with those and try not to let them get kinked. For safety, I removed that little board and just unclipped the sensors, and unthreaded them from a little black clip on the side of that board. Note the heavy foil shield which is connected by "pressure clip tubing" to the back of the key assembly; you need to carefully unclip this first. Remove the motherboard (it is screwed to the back of the key assembly frame carefully, and the little plug-output board. Don't forget to unplug the power connector. Carefully fold back the foil and you will find that it is screwed to the front panel boards. If you don't need to remove them just leave the foil out of the way. Now you are ready to drop the key assembly, which is held in place by the screws in the recessed slot on the underside. It will drop down, so be prepared. Pay attention to the pressure sensor strips at the low end of the key assembly; they come out with the assembly but be careful not to let them get damaged.
    If the problem you have is with the keys or weights, set the rest of the keyboard aside. You can inspect the weights in place without removing the keys, but you can't actually fix them without taking the weight assembly out of the metal "cage" it is in. There are two assemblies; each can be slid carefully out of its end of the cage after you unscrew all of the little screws on the bottom of the metal frame. In mine, the lower weight assembly was composed of three segments, each with about 15 counterweights; the upper note assembly had two segments, each with about 15. I have heard that some weights have been broken because of brittleness (don't store this thing in an attic!!). Except for the back end, which has a red felt strip to prevent key clack when the key is pressed, the weights are pretty light and I'm guessing that you might be able to glue the pieces of one back together, maybe pinning them with a toothpick "dowel" to help. Across the base of the key weight assembly is a thin strip of self-adhesive felt; this is to prevent key clack when the key is released and the weight drops. In my unit, this strip had been installed off center, and it gradually moved toward the back, allowing the front edge of the weight to contact the front edge of the weights' platform, creating the clacking sound. I re-seated this felt strip toward the front and this eliminated the clacking I experienced. You may need to get new felt - or try a really thin piece of self-adhesive weather stripping...If ALL the keys in one or more section(s) clack, it could be that the entire counterweight assembly was loose, and tightening the screws holding the base to the metal frame might eliminate that.
    My problem with the erratic voices changing was indeed linked to the wobbly parameter knob. Apparently it had been knocked askew during one of my travels, just enough to unseat the pot slightly. To inspect this, I had to remove the large bottom circuit board, and that meant unscrewing the foil shield and removing it completely. I discovered that the little selector pot had come loose from the socket. It is held in place by four little tabs, and they were loose. The vibration of playing the keyboard caused the entire pot to jiggle in its socket as a result, and these tabs were also apparently the ground for the pot. Loose ground = loose signal, and the vibration would cause the voice changes. IF YOU REMOVE THESE BOTTOM BOARDS, make sure that when you replace them, all of the switches and buttons re-seat properly and work freely in the front panel. I neglected to do this the first time, and a few of the switches ended up being jammed when I put the unit back together. One result: the unit won't turn on! Luckily, after taking the entire keyboard apart and reseating this board, making sure these buttons were free and through the panel, my ZR-76 worked as good as new when I put it back together.

    This was a real educational experience. But I am grateful to everyone who posed a question and/or provided an answer, because you all enabled me to repair my ZR faster (and less expensively) than it would have been had I had to take it somewhere.

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    Zr-76 repair

    Dear "poefool"

    Your detailed info was very thorough, I just had one question please.

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