I had the same exact "RED disappears" problem on a Golden Tee on location and it had the new neckboard too. I resoldered the transistor, but the problem became intermittent.....sometimes working, sometimes not. Ended up swapping that transistor with one of the other colors and the problem moved to the other color. So I went out and bought a brand new NTE replacement transistor and that fixed it. Remember these transistors are driven very hard to the limit of their specifications (part of Wells-Gardner's poor design) and fail often from heat. Use silicone heat sink grease on these transistors.