Since there is no service manual available on the internet by the time of writing this blog post I thought it might be a good idea to sum up some recommendations. This writeup is about a PN 80 but applies to all pianos of the PN series (like PN 60, PN 70, PN 81, PN 90 and PN 100), since they use the same hardware, basically.
The PN 80 is a 24-note polyphonic piano designed by Kawai in the early 1990ies. In Germany it cost about 3500 DM (~ 1800 €) at the time. It features eight 16-Bit Sounds (2 Piano, 2 E-Piano, Vibes, Harpsichord, Strings, Organ) and has 88 weighted keys. It's not as heavy as comparable e-pianos of that size. It's body is built of less wood and more light metal and it features weighted keys instead of hammer action, that's why.
The sound is a bit cheap in 2018, compared to modern E-Pianos with lots of memory. Memory was expensive back then and Kawai did their best to find a good compromise. But it still sounds a lot better than the sound of cheap newer pianos like the Hemingway DP series.
"Cheap" regarding the PN 80 means from a today point of view, the sustain sample loop starts a bit early and the piano lacks an equalizer to lower the typical japanese sound brilliance. Inside there are only two speakers (loud enough, though) compared to the four and more used today.
The overall manufacturing is very well made and robust. Tidy wiring, separate metal box for the mainboard and controls. Plus not much dust inside despite of me being the first one ever opening it. That's why you can still use it after more than 20 years of intensive playing. Well played, Kawai.
Still, this PN 80 had two major problems.
- no sound at all
- ⅔ of the key weights had fallen off the keys
Opening the piano
Do NOT start opening the piano on the rear. The six screws on the backside hold hinges. Read all of this paragraph before going on.
(Optionally) start with 6 screws (bottom side) holding the front metal sheet covering the keys on the front side but DO NOT lift the sheet before having read the next sentences. Hold it safely while removing the screws and KEEP holding it. Note! There are 4 metal screws and two wood screws in the order M-W-M-M-W-M. Lift the metal sheet carefully since the power LED is attached to it on the left side. Get rid of its screw and finally put the sheet aside.
Then you definitely need to screw off 4 screws close to the edge on the left and right bottom. Lift up the piano top like a foldable cover. Remove the ground leads if you need to enlarge the opening angle, e.g. to reach the mainboard in the metal box inside.
In an earlier version of this blog entry I advised to definitely start with the front metal sheet. This might not be necessary, as N. Lewis pointed out in the comments. Actually, I don't remember why I needed to lift it, maybe it was to access the keys. Try one way or the other and feel free to put another comment below.
Fixing the issues
Oh so quiet
The no-sound-issue was solved quickly. After the usual cleaning plus button and fader maintenance (I use Kontakt Chemie Tuner 600 spray for potentiometer issues) there was sound on one stereo side. It turned out to be a torn volume fader. I got a replacement fader from synth-parts.com. The offered Korg 30 mm fader has the same size and specification.
The PN 80 has quite heavy weights (21 g) in each plastic key to imitate a real piano feeling. Kawai did glue them below the tip of a key. Unfortunately, the glue used here fails after some years of usage so you have to find a sustaining solution.
I've come up with two ideas and I used hot glue for both.
Take the weight (I warmed it before in the sun light), put some hot glue on the bottom and press it back into the designated space in the key. Do that fast since hot glue tends to cool fast when in contact with metal (thats why I warmed it in the sun). While pressing it deep into the key hold the key on the upperside (now bottom side because of upside down; to prevent breaking it) and use some tool to push the metal block down. The back of pliers e.g. will do.
- either scratch some scratches into the key hole (haha) above the block with some sharp knife and put some more hot glue into the whole on the left and right side. The scratches will hopefully make the glue stick better to the plastic.
- or take a short peace of straight spring steel, slightly longer than the diagonal width of the key hole. Press that metal piece in the whole and fix it with hot glue.
You need to do some cleaning afterwards and cut away all hot glue strings between the keys. For the piano I serviced in May 2018 I used the first of these two methods. I'll report back if this does not work in the long run.