Roland TR-606 Mods
This little drum machine is one of the cheapest analog drum machines available, this makes it very attractive to modders. Unfortunately the original sounds are not great but you can rework the patterns live and it has the real x0x interface with accent. You can string four 16 step patterns together and it stores 32 patterns. Its also highly portable and these features make it perfect for quickly getting ideas down.
Quote from the original manual:"The Roland TR-606 is a portable, economical, automatic and fully programmable rhythm device, which can memorize your own rhythms with exceptional flexibility"
The circuits of the TR606 are fairly straight forward and quite simple. This is perfect for modding but due to the size of the device the circuits are tightly packed so you need to get creative with the placement of new parts making these mods unsuitable for inexperienced modders as they require very fine work.
The modifications detailed here have been designed based on several other modders sites most notably confusedmachines. I couldnt work from their step by step instructions so instead copied them out into schematics, simulated all the mods, and made a few slight adjustments. Every mod is unique and component values will probably need to be adjusted for your machine and tastes.
While I can do the mods for you, at $50/h with approximately 16-20 hours of work for the analog mods it becomes rather expensive. I'm providing all the details so you can get in and do the work yourself, the mods provide a huge amount of control over the sounds and transform the 606 into a great analog drum machine while still maintaining the characteristic 606 sound.