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Hi all, I registered here in the hope I might find some help in repairing a lovely little Casio PT-20 I picked up for a couple of Euros in a second-hand shop. It's nice and tidy with no cracks or scratches, and all buttons & keys are present. Sadly there appears to be something wrong with the envelope signal on the melody, and the chord/bass doesn't make any sound at all. Here's a short MP3 which demonstrates what it sounds like, using the rock & bossa nova beats, and piano and organ melody sounds. Clearly a very sick puppy 😟 Some crappy phone photos: The plastic is not nearly as yellow as the photos suggest! I would love to try and fix this lovely little keyboard, but haven't been able to locate a schematic other than for it's much bigger brother the PT-80. This does use the same CPU though, so there's probably a fair bit they have in common. I guess finding the envelope transistor for the melody might be a good place to start; on the PT-80 this hangs off pin #79 on the CPU...

I recently purchased a Casio PT-20 that was listed as "not working" and to my delight, some fresh batteries and the reset button brought it back to life. One issue however, whenever I play press a key, the note plays and then....plays in reverse? Holding down a key will cause the note to attack, sustain, and decay, then ramp back up to a peak before cutting off, as though the envelope is being applied correctly and then backwards. The length of the ghost note follows (but does not directly mirror) the length of the intended note: longer notes have longer ghosts. The ghost note for chords, however, appears to always be short. Here is some footage: I have so far only done basic cleaning to no avail. The only notable detail I found was this white stuff on the board: Is this indicative of failed capacitors? I would be more suspicious if the behavior of the keyboard wasn't so close to spec! I'm going to chase down some leads from other threads on this forum, but I wanted to ask for any tips or ideas of where to start. I'm a little perplexed because the unit is not failing to produce sound or failing to produce correct sound, but rather producing the correct sound...and then some which suggests to me that the capacitors, at least, are all fine. But as I said, I'm new at this. Curious for any thoughts or suggestions on where to go from here!

Hello folks. I am new here, so please forgive me if i mess up. My grandfather had bought my father a PT-20 when he was a teen. It is a very sentimental object to him. As he had been trying to get it back working a few years ao, he used a higher voltage adaptor, burning out (hopefully) a internal fuse circuit.. I hope on restoring the synthesizer, and gifting it to him on his birthday. Any advice? Will be happy to provide any resource that might help restore it.