Repairing a Casiotone 101 synthesiser

As I’ve mentioned in previous posts I am interested in sound engineering and technology, and I love all kinds of music tech although this far outstrips my musical ability. So I’m keen to take any opportunity to get hold of something interesting, even though this often involves working out what to do with it later. I have acquired a number of interesting items this way, some of which I have kept and some I sold on. I still have a Casio VL-Tone VL-1 and I also had a boxed Casio SK-1 although I did sell this one on.

I was at our local rubbish dump the other day, and out of the corner of my eye I saw someone with an obviously old and classic looking synthesiser in the back of the car which was clearly heading for the ‘electrical’ skip. It turned out that this had recently “gone bang” and had been left out in the rain for a few days. The owner was quite happy for me to take it off his hands. On closer examination I found that I had scored a Casiotone CT-101:


I’ve found a few references to this online which are mostly fairly derogatory, and whilst I suppose this is nothing like a Fairlight or even a DX-7 it is still an interesting bit of history, and from a similar era. It dates back to 1981 and must be one of Casio’s first attempts at a professional grade musical instrument. You can see the legacy of the 1970s era ‘home organ’ with the large multi-coloured controls and woodgrain finish. However the sounds are beginning to make the transition from organs to a classic 1980s style synth.

First impressions on getting it home were positive – it’s really well built with a solid wooden case, metal panels and very chunky controls and jack sockets on the back. Unfortunately there is evidence of water damage – mostly to one of wooden end pieces which are chipboard and have absorbed a lot of water leading to swelling and cracking. This is a real shame because this is obviously recent and the rest of it is in good shape.

Given this history of it going bang I didn’t try plugging it but stripped it down to find the problem. The obvious place to start is the power supply, and I was hoping to find a fairly simply fault.


The internal construction is again very well done and surprising simple. The wooden casing is very solid and the PCBs are slotted in to small guides with lots of discrete wiring. There is lots of room inside to work and it’s easy to find your way around. There are a lot of screws to remove at the back and underneath, and the keyboard itself plugs in via a ribbon cable which you can pull out gently from the PCB connector.


A close look at the power supply PSU quickly revealed this:


Most of it looks good but this component (labelled PME 265) has clearly failed. There were bits of it all over the inside of the case, and there was no sign of any other damage anywhere. The damage to the component made it quite hard to see exactly what it was, but after gathering together the broken bits and with a bit of searching around, I found it was a Rifa PME 265 0.02uF capacitor. I think these are used for smoothing / interference suppression in the mains supply.

This specific part is no longer made but a newer version (PME 271) is readily available on ebay. I was able to find a replacement (a PME271) for less than £3. I was surprised by the capacitance rating though, I’ve never seen them measured in Nf before:


The new part is almost identical in size and shape to the old one, and the manufacturer is the same. Replacing it was very easy, just a few screws to release the PCB and I was able to replace it in situ without removing any of the wires by twisting it around and resoldering it. This is the old and new part side by side. No prizes for guessing which is which!


Then it was simply a matter of reassembling and testing.

Then comes the moment of truth… and success! No bangs or smoke, and it works perfectly. I absolutely love the chunky controls (orange and blue toggles and press buttons as seen on the photo above) and the sound is very reminiscent of the early 80s. Now need to think of something to do with it… although looks great in my ‘home studio’!


9 thoughts on “Repairing a Casiotone 101 synthesiser”

  1. Amazingly helpful, thanks, I had a non working Casio and wouldn’t have known where to start until I found your post. I found the same part was damaged and a fuse blown and have just fixed it! Have never done this kind of thing before so feel inordinately pleased with myself so thanks a million!

  2. Wow! It seems this particular model has a tendency to go ‘bang’ at some point; my own included.

    Though digital, the organs on the 101 can give you that floyd’y’ transistor sound,especially with the vibrato. And as you say, it does look cool and is built like a tank.
    Good job fixing it!

  3. I also have one and it works except none of the E keys play and some of the F# keys don’t play as well. Any thoughts?

  4. If it is a series of keys that aren’t working, I wonder if there is a problem with the ribbon cable between the keyboard and the main board. It uses those flexible conductive strips which get quite brittle and often break when old. I’ve had this happen with some old computer keyboards in the past. This is potentially good news as it means that if you can fix it you will fix all the broken keys in one go.

    What I’d suggest doing is first of all strip it down and remove the keyboard, pulling out the ribbon from the main board. Then have a close look at the socket and the end of the cable. I’d give the socket a quick clean up and maybe a small dose of contact cleaner.

    If the contacts on the cable itself look damaged or broken, you can should be able to cut the end off (sounds a bit drastic but I’ve done this before) and expose some new clean contacts. This is a bit difficult to explain, but because the ribbon doesn’t have a plug on the end and just slots straight in to a set of contacts you can just cut off the end and start again. You only need to cut a small amount and you have to be careful that there’s enough slack left over.

    Probably before cutting anything I’d just pull out the cable, clean it all up and put it back. That might be enough by itself to remake the connections

    Does that make sense? Let me know how you get on!

  5. I’ve just got a 101 and everything seems to function fine apart from the fact that when plugged into my amp, pedals, or headphones it is making an unpleasant humming noise which makes it almost unusable. When using the internal speaker the hum isn’t there however. Maybe a grounding issue? I’m gonna open it up soon and see if I can figure out what it might be

  6. Yes that does sound like a ground / earth issue. Would be worth making sure the internal ground connections are sound, and that all the sockets etc are properly connected to it. There is is lot of metal in that case! Puts modern plastic stuff to shame.

  7. Hello, I have just been “given back” (by my grandaughters) my old Casiotone 101 originally from the 80s/90s and the volume control knob is missing. Have you any suggestions, please, how I can replace it. Everything else is in perfect working order. Many thanks. Richard (Hummerston)

  8. I think your best bet here is going to be to find a brand new replacement on ebay or similar. I don’t think you will be able to find an exact replacement as these are not popular enough for people to stock them or sell replacements. There is a wide range of knobs you can buy and given that there is only one on the 101 you don’t need to worry too much about matching it up. So I’d suggest finding something that you like which matches the colours and looks retro. Maybe a volume knob from a classic Strat guitar or something might look good?

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