The service manual is not really going to tell you how to change a bulb in that radio. I am not sure there ever was a separate “service manual” for the radio, like many of its day it included a service section with block diagram, theory of operation, and schematic in the manual that came with the radio. It was expected that if you knew enough to read the schematic you probably did not need step-by-step instructions on how to get to a bulb and replace it.
To get to the bulbs you are going to have to open it up by removing the top cover, there is no need to “take the radio all apart”. This should be pretty simple, two screws on each side if I remember right. I do not remember any screws on the back of the HA-600 (to just remove the top cover).
User manuals can be found at mods.dk or at
http://www.vmarsmanuals.co.uk/archive/4028_Lafayette_HA600_receiver_manual.pdf
As for an antenna, just try around the ceiling first. Inside antennas are always a compromise, and don’t expect world class performance, but it should work. Yes, you will have some noise issues, as you will be close to all the noise sources in the room/apartment/house. Part of the reason outside antennas are better is because they are farther away from lots of noise sources. A single piece of wire looped around the ceiling of the room is a good starting place. You do not make a big closed loop with it, the far end is not connected back to the wire anyplace, it just ends.
With these kinds of radios it is always hard to tell what freq you are really on. If the dial is accurate (unlikely) the graduations are too course to get precision out of. Often if you can tell within 50 kHz that is pretty decent, and there can be 10 transmissions in 50 kHz on HF. But, this is what we all had to deal with “in the day”. It can be frustrating to a person used to relatively exact digital frequency readout or even channelized scanners when you pretty much always know what freq you are on. It used to be pretty common to use something like a BC-221 or LM-18 heterodyne frequency meter in association with such radios, then you could tell your tuned freq within 1 kHz, often down to 200 Hz.
T!
