I suspect this Wasp was bought of ebay here (at Matrixsynth) as it had the same crack and the cloth tape on the back. The drone is caused by a faulty AR (with broken CMOS IC’s) not capacitance.
The wasp is deceptive, not only does it make really nice rich squelchy sounds for something that looks like a toy, it is also very hard to repair! The main problem is the low quality of the PCB combined with the fact that all the knobs are directly mounted to the PCB board and nothing else. So any excessive pressure on the knobs can cause havoc to the traces and components mounted around the control knobs. Another issue is that the wasp uses a lot of CD4xxx CMOS IC’s that are known to degrade as they get older. 1
The customer just wanted it to work so little was done to the cosmetic condition of the Wasp apart from cleaning. The case is made from a 2 vacuum formed pieces of textured (I think its called ‘haircell’ ) ABS clammed around the PCB.
A common problem is that the screws eventually shatter the plastic around the holes meaning a lot of them end up being held together with duck tape! You would be hard pressed find a wasp case without this problem today. The case and keyboard definitely have a lot of influence from another synth made in Britain … the Synthi AKS keyboard which was also touch sensitive and vacuum formed texture case.
All the IC’s I replaced were socketed, which prooved quite difficult as the PCB is double sided but not ‘through hole’ plated. The main failing IC’s were the D Flip Flops (4013) the analogue gates (4016) and the inverter buffers (4069.) Although ideally I would have replaced the lot. The keyboard design is fascinating (if you like that kind of thing) the designer Chris Hugget used an array of analogue multiplexers to create a big scanning circuit that makes the single capacitance detecting circuit scan the keys and detect which key the finger is on and for how long, I could see a lot of potential in it for making it polyphonic and pressure sensitive.
I did not manage to get a sound sample of it, but I have another Wasp on the go so more on wasps coming soon! But below is a video of me testing the keyboard Mid-repair ……