On Feb 23, 2010, at 5:58 PM, Steve Ridley wrote: > instead of a keyboard. Serge replaced them with the (vastly better) PCO and NTO around 1976. While we're on the topic, I've got a PCO. I don't recall seeing the schematic, but it's got a 3046 on it, so I presume it's been used in some sort of "heater" configuration. - Aaron