Now, I might be wrong on this, but I have done ALOT of research on the AR3500.
I have read someplace that if it is only showing 0's that it is the CPU that has gone faulty. Again, I could be mistaken, but that is what I believe I came across.
I know there are alot of different CB shops out there, BUT, the best one to consult with concerning this radio is Bob's CB shop. I used to be a Registered tech for Clear Channel.
I am not trying to scare buyers off with this post. And again, I might be completely wrong. There is plenty of documentation and forums about this radio. I know because I own a working one and wouldn't mind having a backup to mine for parts.