Tanks, Bob
If this is the "Royal 1000", you can find the service manual for it here on Nostalgia Air at:
http://www.nostalgiaair.org/NostalgiaAir/Manuals/Index.asp
It is listed in the "Radio" section, as "Zenith 'Royal 1000' Transoceanic - Service Manual". It includes schematics, parts list, service information and a dial chord string diagram.
Hope this helps,
Richard