Hi Jim, >documents. I once contacted Collins Radio regarding the 618V-1 and they I don't have the 618V-1 anymore but I remember that it did have a single 9 pin minature tube in it. There were 2 sockets but only one tube. It was potted with low density foam so it was clear that the second tube (if that's what the socket was for) was never in there. Tom Bryan N3AJA