If I'm reading you right, you are seeing the
ghosting even with the decoder disconnected from the dimmers. The most likely thing to try is to adjust the low
trim setting on the two ramp cards to the left side of the front panel. Get a straight-blade jeweler's screwdriver about 1/16" wide, and gently find the slot on the rotary
potentiometer just inside the hole (it's easy to miss, plus you have to guess a
bit about what angle the slot in the pot is already positioned in). Tweak it slightly clockwise (iirc) until the
ghosting stops, then do the other of the two ramp cards. The left card controls 1-3, the right one controls 4-6. After that, I suggest getting two matching fixtures and plugging one each into channels run by each of the two cards, and using the
console to see if they still start glowing at the same
point on the crossfader. If not, keep tweaking until they match, yet don't ghost.
While you're there, you may as well touch up high
trim as well, I usually compare it to the test
button level, tweaking down until I see a difference between test on and test off, then give it one slight tweak back up to match. Older packs had separate pots for each
channel, later ones had a single high
trim for the three
channel ramp card.
If the dimmers stop
ghosting as soon as the decoder is disconnected, then you have a problem with the decoder.