I was sent a a Buchla 284 for repair and photographed it for this page.
The rear PCB has a jumper JP1 for internal/external +24V near the power connector. On this PCB the settings are unlabeled but internal is jumpered as shown, the two pads farthest from the PCB edge.
There are two trimmers per channel. One trimmer calibrates the Delay and Duration controls. The other trimmer calibrates the Attack and Decay trimmers. I typically calibrate for mid-control or maximum time, so either at the 0.5S or 10S setting. This photo shows the location of the trimmers.
|TR1||Channel 1 Delay/Duration|
|TR2||Channel 1 Attack/Decay|
|TR3||Channel 2 Delay/Duration|
|TR4||Channel 2 Attack/Decay|
|TR5||Channel 3 Delay/Duration|
|TR6||Channel 3 Attack/Decay|
|TR7||Channel 4 Delay/Duration|
|TR8||Channel 4 Attack/Decay|