MERCURY RISING PRODUCTIONS

KEYBED/KEY REMOVAL

The first step after removing the screws that hold the key assembly to the chassis is to carefully wiggle out the keyboard ribbon connector from the main circuit board, NOT the connector that is attached at the keybed itself, because that was factory heat soldered and will never go back together properly if removed.  There are several black keystop strips on the underside of the keybed that have to be removed first, then simply push the keys back and out and they should come out easily.  The whole operation only took me one hour from the very first screw to having all the keys in a bucket for the remaining steps.  I also removed all the key springs and set them aside for cleaning and re-lubrication.  I also cleaned and inspected the contact board but did NOT remove the actual key contacts as all the keys were working on the unit.

RED GLUE REMOVAL: CAUTION IS ADVISED!

So, someone along the way found out that sodium hydroxide, or lye solution or by its other name caustic soda, will break down the epoxy over time and not harm the plastic keys.  This is EXTREMELY DANGEROUS stuff to work with so this was my procedure that worked.  I purchased two 15 litre plastic pails from our local Home Hardware store, a pair of chemical resistant long gloves, the granular lye crystals, a pair of 3M safety goggles that completely seal off your eyes, and a plastic long handled scrub brush.  First I measured out 4 litres of plain cold water into one of the buckets (the other one had the keys lined up in it) and mixed in approx 200 grams of the lye crystals and mixed them using the scrub brush all while having a long sleeved shirt, goggles, gloves and a beanie in case it splashed onto my head!  I then poured the solution into the bucket with the keys and kept it outside in our garage because of the VERY strong fumes from the lye solution.  I recommend keeping it out of animal/children reach.  This stage took only about 1/2 hour.

RED GLUE PART TWO

After two days I checked the keys and found that all the weights had dropped or did drop out just by turning the keys upside down and most of the black keys as well,  Using a pair of long needle nosed pliers, I gently pulled out some of the remaining black key weights, but four of them would not budge and one while key was stubborn as well, so I removed all the weight free keys and weights from the bucket of lye, put them into a clean water bucket and added about another 50 grams of lye, mixed it, and put the remaining keys in.  Two more days later, the weights again just dropped right out, so I put them into the clean water bucket with the remaining keys and weights, double checked the solution for remaining weights and took the bucket with a secure lid down to our hazardous waste disposal for safe disposal: it is advised to NEVER just pour out the solution down the drain or into the environment.  Add another 1/2 hour to the project total.

CLEAN KEYS AND WEIGHTS

Now for the not-so-dangerous part: cleaning the keys and weights.  So, with the second pail at hand, I mixed a strong solution of dish soap and hot but not boiling water  and using my Grease Monkey gloves, I used the scrub brush to wash off any residue/solution leftover and then immediately rinsed the keys off and put them into a box for the re-glue step of the operation. The last things to wash were the key weights: I also dried them off and put them into a sealed plastic bottle for now to prevent rusting.  Two of the keys were stained a bit from being in contact with the keys weights, but it just took a little extra scrubbing and new hot water soap solution and they are good to go.  I had picked up two epoxy kits as 2 part epoxy is recommended from people that have dealt with this before and seemed to have success with it.  This part of the operation took about 1 1/2 hours.

RE-GLUEING ACCESSORIES

Now to re-glue the weights to the keys using Gorilla Glue Epoxy: accessories include having a clean cloth, 99% Isopropyl alcohol, many Q tips, needle nose pliers, a metal push stick and lots of patience!

RE-GLUEING THE BLACK KEYS

Just so nobody makes the same tiny mistake I did on one black key: make sure that you mix just enough epoxy at a time to do no more than 4 keys: I tried pushing the limit and the epoxy hardened enough that one of the black key weights would not push down far enough into the well.  Luckily it did go down far enough to clear the guide pin which sits at the front part of the key weight well.  As you can see in the pic, you just need enough to seep out around the weight but not enough to fill the front well: I used the alcohol and Q tips to ensure it was clean, as it easily came off before curing.

KEY INSTALLATION

Finally at the point where the keys can be re-installed!  I used the 99.99% Isopropyl alcohol to clean any remaining discoloration and or goo from the keys as I installed them one at a time, black keys first.  I cleaned the contact board and remaining old lithium grease and applied the new grease to the two points where it was needed: many more keys to go!

THE BLACK STRIPS

....which I almost forgot about but didn't!  So these strips hold back the keys from moving forward and releasing kinda important, but they were initially glued in using double sided tape as far as I could tell,  Instead of messing with trying to remove the old tape etc I just purchased the Gorilla Clear glue and appliled little dabs here and there along the tape: one word of caution: while doing this I discovered that you have to make sure that the keys are indeed seated correctly by pulling them ALL the way back.  Another discovery was that one of the strips is labelled HIGH and it is rather important to put this one on the highest keys or it won't fit!  Lessons learned as I go along.....

THE BATTERY

So with the keybed re-installed and the ribbon cable from the keyboard carefully re-seated after a bit of Deoxit applied, I looked over the main board one more time before closing her up and noticed that there is a battery test point clearly marked on the board.  It measure 2.78VDC, so I thought why not change it since I did have one last new one in my shop.  When I removed the old battery, sure enough it had just begun to leak and corrode, so I cleaned off the residue with more Deoxit and it was good to go!  I tested the voltage of the new battery which was a CR2032 and it read 3.24VDC so it should last about 10 years before replacing.  If nobody opened up the JD800 since it was purchased, then the old battery was in there for about 25 years which is WAY to long!

THE END...I HOPE!

With the battery replaced and one last inspection, i closed her up and tested the operation of the keyboard and much to my surprise even the aftertouch worked!  I then loaded in a new set of film score sounds and enjoyed the newly refurbished JD800 in all its glory.  I may recap the power supply and change the display but that will be for another project.