By: Brad Burt - RedHouse
The original version of the Forum-Vibe circuit board was actually an offshoot of my Classic Vibe rev-4 (R4) board and used PIHER trimers (which I much prefer), the R4 board was designed so the trimmers installed with the pins oriented in a way that when you turned the trimmer clockwise (CW) you turn the bulb bias and bias offset adjustment UP just as you would a volume control. Why does it matter? well later on when your vibe is fully assembled with light shield in place you can't see the bulb so you'll need to know which direction of rotation turns the lamp bulb UP or DOWN.
 Rotation & Pins |
 PIHER |  BOURNS |  BOURNS |
Here is where the "problem" first appeared on the original R4-F board, as can be seen above pins 1+3 are physically in different positions which cause one to have to turn CW or CCW for the same effect. If you spin the Bourns pot around it physically fits the solder pads but the rotation is opposite and setting the 1/3 mark is different relative to pin-1 and pin-2.