Hats off to MetraCollector for such an informative post. I have just picked an HP54503A and it is giving exact same errors. I will try to fix it on the same steps as mentioned in the first post.
Sorry about bringing up an old thread but it was such a nice info that I could not resist paying thanks to MetraCollector.
On mine, Dallas is already an issue but on calibration, it gives following results. After calibration, Ch3 and Ch4 work but Ch1 and Ch2 don't. Any thoughts / advice what to do next ?