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)So I got this poly-61 years ago, literally years ago, I guess nearly 3 years. I bought it as junk, and the joystick plate was unpopulated when I got it. So I tried to find a joystick to buy for years, only 1 time I had the chance to get 1 from Germany in all that time... but I was too slow and someone else bought that 1.
So recently I decided to open it up even if I didnt have the stick, just to repair the inevitable battery leak.
Well surprise surprise, the joystick was inside of the poly61, seems it had taken a fall sometime before I got it, it completely disassembled the joystick and left the pieces within the interior like beans in a rattle. After reverse engineering the joystick and reassembling it correctly, I attempted to tackle the battery leak.
The battery leak was nowhere nearly as rough as some other poly61s I have seen photos of, although it was still there. I cleaned the board once or twice for 4 days straight, using vinegar, and alcohol.
The bottom of the klm-509a board developed a white film almost entirely over the board after cleaning.
Seems it was either a wax layer or no clean flux, but I doubt it was flux since it covered the entire board nearly.
Cleaning the top was interesting, since the board is populated I couldnt get underneath most IC's and tight nooks and crannies. I also didnt use any baking soda on the component side (out of fear it would cause more trouble in the long run if not fully cleaned/removed)
Well, the top developed a white film in places as well, most notably between legs of components, on many IC's the film is between every leg where if it was conductive it would bridge.
Anyway, I used a coin cell holder for the battery, and I removed the resistor on the charging trace and used a diode there. I put the diode in backwards at first and it created a short where it grounded a section of the panel(program/parameter), after turning it around the right way, everything seems perfect, the display lit up P161, then 11-11 as it should. all front panel buttons function, etc.
So I find a patch tape dump .wav file and try loading the patches back on, using multiple tape dumps from multiple sources, but no matter what I do there are notes hanging.
The first program doesnt hang, but nearly everything until the 50's has notes hanging/playing as soon as it goes to that program. If I noodle around, the hung note changes occasionally to whatever I had just played, seems to have correspondence with certain octaves maybe?
So out of all the programs only a few are not hanging.
Also on many voices with hung notes, if I turn sustain to 0 the hung notes disappear, but so does sustain.
So long story short, tried replacing the battery, put in a coin holder, put in a diode to replace the charging resistor, loaded patch tape wav file, but on 97% of programs/patches there are notes hanging randomly.
Any ideas of what might cause this? Is it the keyboard? maybe still some corrosion hiding under some IC's? cold solder? bad resistor?
I should add, when the joystick was exploded on the interior the copper axis of the pitchbend pot (if I recall)
was wedged in the keyboard under keys, luckily I found that, but if there was some foreign piece of metal still in there, could it cause that?
I also am not 100% certain where the little black ground wire for the keyboard belongs, I attached it to the chassis of the keybed, but I noticed a piece of paper attached to the keybed PCB with aluminum inside of it exposed for the screw head to make contact. Can anyone confirm if that black wire right beneath the middle of the keyboard belongs on the paper or the chassis itself?
Its so close to being A-OK. Any advice is appreciated. Thanks ahead of time.
