Not a '77 model, but I did buy a 2B-LP in the 80s, and own one now. The 2B is a great amplifier. I don't know how much the performance changed from the 2 rack space 2B to the 1 rack space -LP version. The only complaint I have with my 2B-LP is the noise from the transformers. I have the block transformers version, not the torodial version. The noise is not in the speaker outputs, just buzzing directly from the transformers themselves. Not sure if the older 2Bs also suffer from transformer buzz.
If it works and the transformers don't sound like a bees nest, buy it, service it, and keep it.
