The obvious faults, like damaged connectors, broken wires and cracked cases are usually straightforward fixes, although with a caveat that some connectors are unique to the product and exact replacements are often difficult to obtain
If a unit’s just hung-up, behaving oddly or not powering on, this can often be remedied using a factory reset procedure. Performing this is sometimes just a case of pressing a recessed button for a given length of time, or holding down certain keys or buttons while power is applied. Sometimes however specific boot software is required which is usually on the disk or memory stick which has long ago been lost or discarded. If this information can be downloaded from a manufacturer’s website it could be possible to resurrect a recalcitrant device
If however the problem is with an on-board processor which holds the unit’s operating code, then a fix may not be possible. If the processor/EEPROM/FPGA in question is loaded with software at the factory, then even being able to buy a replacement physical chip won’t solve the problem, since the on-board software may either not be available or need specialised equipment to upload it
It’s best not to jump to conclusions before giving a unit a few coats of looking-at though, so if you have a cherished instrument which now doesn’t make the sounds it’s supposed to, please get in touch and we can have an investigate