main board in ODS -- is there a standard?

[jaysg]

Is there one unique board layout which serves for HRM, non-HRM, classic tone stack, skyline tonestack, and Bluesmaster? There seem to be a number of OD entrance variations also.

[jborders5]

There's not one exact standard, but the overall layout hasn't changed much over the years. The OD entrance & PI trimmer are the only major differences between the main board layouts from the 70s through the later HRM amps. You can make any layout work as long as your main board can accommodate those two differences. Attached is the board I sell to scale with 3 different layouts. Please note I did not error check the layouts, so don't use them to build an amp.