Advice please
old raymarine c80 connected to raymarine /Raytheon 120 GPS receiver/a
ntenna.

losing "fix" of GPS ,with increasing frequency
recoves when c80 turned off for a while,lasts then minutes- hours only

checked GPS unit,has soldered in battery (battery replacement suggested on forums to enable gps to ember position etc)
since touching the bloody thing unable to get a fix at all!

i assume it's past it's use by,And/or has a loose connection within the unit.

i plan now to replace it with a digital yacht gps 150, though I will probably try replacing battery first.

thoughts and experience would be most welcome