It is not really possible (at least thus far) to build an analogue copy of a Roland TR-808 without these specific transistors. Some clones have been released and some people have even attempted to build a DIY version using standard 2SC828’s and they discovered that it sounds very wrong. That’s because there is no transistor or zener diode on the planet that has the exact noise spectral profile and output level of the 2SC828-RNZ transistors from the specific 1970’s batch that was used in the production of the TR-808. If the transistor fails in a TR-808 it must only be replaced with a transistor from that original batch or it will no longer sound like a healthy TR-808. When Roland ran out of them they had to discontinue production of the instrument because the noise characteristic of these transitors is crucial to the all important snare and hand clap sounds and that white noise is also then filtered into pink noise for other sounds in the instrument. If you put a standard 2SC828-R into a TR-808 in place of the noise selected part the sound completely changes. As mentioned earlier in the article these transistors are in fact not technically speaking 2SC828’s, if they were they would not have been rejected so putting a 2SC828 in place of Q35 is futile, it’s the wrong part. Fortunately the transistor is not prone to failing so if you own an original 808 then it’s not something you should worry about.
This post on the history of the 2SC828-R transistor central to the Roland TR-808’s sound reminds me of Steven Johnson’s podcast that explored stretching instruments to breaking point. I am intrigued at the idea that to get the sound, Roland sort transistors that were deemed to be ‘out of specification’.