I'm going to try out a late 60s, early 70s Alamo Challenger amp for sale. I would really appreciate any advice anyone can give about what to watch out for. The owner thinks it is all original except for the tubes, and the speaker. It still has the 2 prong cord, so it seems likely that it is all original inside, though I hope to get a glimpse of the guts. He says it has NOS GE power tubes and a Weber 10a125 speaker, and he says it is in "fantastic" shape. Does anyone know what Ohms the output transformer on these expects? He said the Weber is 16 Ohms, but he doesn't have the original speaker, and I'm not sure that he is even the one that replaced it. I'm not too concerned as long as it is working right now. I'm sure it is way due for service, so I expect to have it worked on, so if it sounds good, I will grab it. I'm not too worried, since the price is very good. Any advice will be greatly appreciated!