Here are my findings. I went from the two small sockets like you said, from socket to socket was 586.4 ohms and from socket to gound on both read 281.1 ohms each. I just oreder the schematic/service book for this unit so it will be a few days till i get it. From these finding is this too excessive? When my manual arrives I will let you know and you can tell me what tubes does what and test them. If there is something else you would like me to test in the meantime, i'm all ears.
Thank you.
