MODIFICATIONS
ART USB Dual Pre
Behringer B2 Pro
Denon DP-61F
Dynaco ST-70
Hafler DH-110
Hafler DH-500




  Hafler XL-280
Klipsch Promedia 2.1
Nakamichi CM-300
Scarlett 2i2







CME UF8 MIDI
UPGRADES and MODIFICATIONS





My town holds a 'bulk trash month' twice a year. During this time people are allowed to put old junk on their curb for disposal...matresses, tables, housewares, etc. So imagine my surprise when I drove past a house and saw mixed in with a pile of old chairs...a keyboard. Intrigued I pulled over and put the heavy and unfamiliar model in my trunk.

Once home I began to clean it up...it was in excellent shape with no scratches and was covered in old dust and dirt as though it had been in a garage for years. I went online and found it was only 10 years old and that this stylish 88-key midi controller was the flagship model made by CME around 2006. It had great reviews and was their only model with fully-weighted piano action, velocity settings, and a nice "aftertouch" feature.


   


CME doesn't support this board anymore and the latest
USB driver was written for XP...meaning that USB use with Windows 10 is not an option. But because this board is the 'real-deal' it also has a 5-pin Midi output...so who cares about the lack of USB support? Considering I got this for free makes this really great project...a couple of hundred little parts forming a giant jigsaw puzzle...and when optimized produces beautiful music...nice.

KEY REPAIR
Despite the UF8's scarcity there are several good tutorials online about fixing common problems.
The main issue is that with age keys can stick down or not return to rest properly. I was lucky that I had only one black key that was affected...but that's one too many(!) So I decided to immediately take the keyboard apart. I suggest you watch the video tutorials online to see how to remove the octave modules. Once you have it removed here's how to modify the sticking keys.

THE CAUSE: A smooth aluminum rod runs down the length of the module and passes through a plastic bushing in each weighted hammer. The bushings can deform over the years, increasing drag on the rod. CME doesn't sell new hammers as far as I can tell...but these are easy to repair.

Note that each white & black key has its own hammer shape (tall/short). The hammers are identical so no worries about mixing these up...as long as the hammer shape remains in the right slot (see image below).

   

Below is the bottom view. A thin strip of masking tape runs down the edge. This serves as a gasket between the two bumper circuit boards that run the length of the unit. I replaced them with a continuous strip of blue painters tape cut to size.

   

BELOW: The rod easily presses out of the module using a screwdriver. Made out of aluminum it shows light marks from each hammer and has a shallow groove machined the length of each side. Don't sand the metal/use a scotchbrite pad/or use a paper towel as these will scuff the surface. I used a ball of soft cotton "wadding polish" found at the auto store to polish the rod to a mirror sheen. After the wadding I used a microfiber towel to produce the perfect finish.

 



 

One proposed fix for the hammer bushings has been to run a 5/16" drill-bit through each hole with a power drill. I think its critical to maintain the correct inner diameter and geometry and not introduce any slop to the action. But I'm not confident that I could drill 88 hammers and maintain a perfectly aligned bore and smooth surface. Trying to use a dowel with sandpaper to open up the bore is asking for trouble as well.

So I was pleased to find that the smooth-end of a 5/16" drill bit fits exactly into the bore and the round edge re-forms the hole. I pushed it through several times from both sides. NOTE: make sure the bit has a sharp leading edge, not beveled, so it will cut. The result was a hammer with a perfectly round hole in factory dimensions that rotated smoothly on the aluminum rod. I did this on all my hammers but still had a couple that resisted this treatment, so I twisted a the fluted part of a new 5/16" bit though by hand. I could feel it cutting slightly and saw some small white shavings emerge. On installation the action was now smooth. So either method will work depending on your severity of binding.

   

KEYS CLUNKING
Some have reported clunking from the keyboard action at times. A cause can be the 5/8" wide, 1/4" thick strip of green felt known as a
"hammer rail cloth" which dampens the hammer as it returns to rest. On mine the hammers had slightly cut into the felt in places and allowed the hammers to come within a mm of the bottom plate, which would explain why energetic playing would cause the hammers to thunk. In addition, if the hammer ends drop too low this adds extra weight when depressing each key.

   

As a fix I considered buying a new felt bumper from a piano supply house, but I was anxious to get things working so I went a simpler route. I noticed that the bumper was simply three strips of green felt glued together. So I peeled the top layer off and added a stick-on length of new generic felt down the entire length. This appeared to bring the hammers up to stock height with about 1/4" of clearance between them and the back plate. I also added a layer of sound dampening tape to the back plate under the hammers to dampen any resonances.

   

LUBRICATION
The factory used what appeared to be silicone oil on the rod and hammer bushings, and silicone grease on the plastic hammer "hat" and contact points. For replacements I had to be careful as lubricants such as graphite, moly, oil-based greases and even some silicones and white lithium greases can damage plastic parts. This means no aromatic 'rust busters' or automotive lubes.

For the plastic hammer bushings I used CRC 2-26 precision spray lubricant which is an electrical-grade lubricating oil and is plastic-safe. NOTE: CRC also makes a heavy-duty silicone which is listed as not safe for plastics...which reveals the difficulty in choosing the correct oil. I lubed the entire rod and its channels as well as the hammer bushings (the sides included).

Every silicone grease I found was intended for plumbing or car repair and I had concerns they also included harmful petroleum additives or PTFE. I wanted this keyboard to last for years and the thought of using a lube that might slowly erode the plastic was worrisome. For the white plastic 'hats' and contact points I bought a 2 oz jar of Trident pure silicone grease which is used for diving equipment. The diving community is well-aware of the deteriorating effect of petroleum on plastic/rubber so you can be sure this is the right stuff.

Also, there are six square plastic standoffs running down the length of the backboard. Rather than rely on gravity to hold them I glued them down. I left the trimpots alone....and the circuit capacitors are too new to consider replacing so I also left those alone.

RESULTS

I spent a few hours putting everything back together. There are about 300 small screws which are a bit tedious to reinstall. If you lose one go to the hardware store and get some #6 size, 1/4" to 1/2" in length in stainless steel. I used the silicone grease to lube the key's pad and contact points and began reinstalling all the keys, checking the action and height as I went.

Incidentally, each white key is stamped with a number 1-7 (black are 3) to help you reinstall them in order so don't panic if you mix them up. The exceptions are the first two white keys which are stamped 00 and 0. The final high key is labeled 8. The result of these mods was a nice smooth key action with consistent feel on every key and sense that this keyboard had been resurrected. What a great keyboard and fun project.

   


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