I've learned a lot over a couple years but I'm still able to come up with stupid questions. So here goes. I was called to check a system that was installed by someone else 7 or 8 years ago. Vista 600 watt transformer with two home runs (12 gauge) both on the 12v tap. Primary voltage is 123v. At the 12v tap under load, I read 11.5v. Two well lights only 4-5 ft from transformer read 10.3 v under load of 35w pars. Only four feet farther are 20w spots that read 9v. There are other spots and area lights so (without seeing the wiring underground) it looks like the total wattage on home run #1 is 220 watts. The home run #2 apparently goes to the opposite side of the front entrance, at most, 30 ft away. There apparently is not as much fixture load on this side and yet the two well lights here measure only 8.6v and a couple other fixtures on this side show 8.4v. The simpleton's answer would be to move up on the taps to whatever voltage provided the desired voltage (11.2-11.4) at the fixtures. Without digging up all the wiring, I have no way of knowing the wiring method or the quality of connections. But I would feel a lot safer rewiring everything. Actually, I would like to scrap the professional (but cheap) fixtures, too, but I don't think the client would approve the budget. I hope I explained this well enough for your suggestions. What's your opinion on the wiring? How about the transformer?