The LED’s are on for such a short time they don’t always get captured in the video frame, but I’m sure you’ll get the idea.

This is a video of my Tiptop Audio Buchla 281t. I think the “trig” button for generator “B” is faulty. I’m pretty sure it’s stuck internally in the activated position - it stiool moves normally.

The video starts with testing the trigger buttons. Each generator starts with the mode selector switch in the trigger position and then switched to “gate” mode. All is well until we get to “B”. As soon as the mode switch is changed to the gate position (without touching the trigger button) , the generator is wide open - constant dc voltage instead of an envelope and the LPG is wide open. When switched back to “trigger” mode the sound stops but the button still has no effect. The same thing would happen if all this were done with the button held down.

The next test is to apply an external trigger in to each generator. With an external trigger even generator “B” works fine. So there probably isn’t much wrong with the envelope generator part of the “B” circuit.

The third test is to apply an external trigger to the “A” section (without using it’s output to drive my LPG) and patch it to the trigger input of each of the other generators in turn. Gens “D” and “C” work fine. As you watch the test of the “B” section you see that the yellow LED on gen “A” is on constantly and the LEDs on gen “B” never light up and no envelope is generated. So the red jack (yellow LED) on the output of the generators doesn’t like being connected to the “trig” in of generator “B”. I was able to duplicate this problem on gen “C” and “D” by patching from gen “A” to the trig in and holding down the trigger button on the driven gen. Same thing… no envelope from the driven gen and yellow light on output of gen “A” stays on constantly.

There is access to the trig button connections from the back side of module. I was able to verify that the switch for the “B” gen was stuck. Not the button itself but the inner workings. I tried a homeopathic dose of very high quality contact cleaner and the switch is now working properly.