My amp is a Laney AOR pro tube 50. According to some writing on the chassis, it was built in '89. How can I tell if it still has the original caps? If it does, what are symptoms of them needing to be replaced? And how much would that cost? Thanks!
really only a tech could answer that. electrolytic can last for 20 years or more depending on the conditions they were used in.

shouldn't cost more then 50-60 bucks for parts. plus 50-60 for labor or more depending on how the caps are to get to.
Prs se Holcomb is the answer
If the caps are bulging outward (usually at the top), they need to be replaced. If not, they probably don't. Or if the amp is blowing fuses and other things have already been ruled out. Many people will automatically recommend a cap job based solely on the age of the amp. While a cap job won't hurt anything, it's often unnecessary and doesn't at all improve the tone or performance of the amp.
Bruce Clement
BC Audio Hand Crafted Performance