The Buchla 100 Numbering System

board revision identification

Originally, when modules were taken apart and studied, there was no consideration for version control, as common knowledge did not allow possibilities of multiple versions of different modules, even though common sense dictated that they probably existed. There are few modules that are whispered about in the forums when it comes to alternate versions (158 and 258 being the culprits), but as more module photos were obtained it was noted that there are multiple different versions of most Buchla modules.

This came to light with the first discovery that there were two different Model 140 Timing Pulse Generators in the Stearns’ 100. Since the project aimed its’ sights on documenting everything, a quest to collect every board layout had begun.

There are some standards to board version suffixes, but there are also some unknowns. Here is the information as we have digested it. Keep in mind this is not a hard and fast subset of rules but it can help identify a circuit the moment you see it.

Circuit Board Suffixes

Three 140s. From the far left, the early San Francisco Tape Music Center, CBS 140A, and CBS 140A1, in respective order. In this instance, the “1” dictates a layout change, to fit parts kludges into a cleaner layout. SFTMC 140 and CBS 140 are different circuits. Another note, the first 140 utilized point to point wiring, so there exists a version BEFORE the board was laid out.

Four of the five revisions found of 158 Dual Sine Sawtooth Oscillators 158a is superimposed as our photo has the numbers obscured

Here we have four of the five known 158 Dual Sine Sawtooth Oscillators, missing is the Mills College prototype 158. From left to right, SFTMC 158, SFTMC 158a, CBS 158A`1, and the CBS 158B. Again, these oscillators are different as the company name changes. The early 158/158a relates much with the 144 Dual Square-Wave Generator’s layout.

Some of these suffixes follow a pattern, some do not. What we can deduce from these numbers is that letter changes indicate circuit changes, and these letter changes can even present themselves as case sensitive changes. Numbers appended to the letter usually indicate layout refinements. We will go into more detail on each module on their respective pages.

140 - Small MODEL NUMBER fonts GENERALLY indicate earlier revision S.F.t.M.C.

140A - LARGE MODEL NUMBER FONTS GENERALLY INDICATE LATER REVISION SFTMC, BUCHLA ASSOCIATES, AND CBS.

There are some exceptions to this rule, like the 191 Sharp Cutoff Filter, 123/146, and the 156 Dual Control Voltage Processor. But we point this out to let collectors know — if the Model Number is tiny, its a good chance you own the original version of the module. If your module has a lettered suffix, you can bet one exists without any letter at all. The “A” revision is NOT always the first version.