Should i have my Harmon Kardon repaired or replace

I would replace it, if your brother gave it to you, at this point it owes you nothing. As old as it is, chances are repairing it, may only obligate you to invest more if it breaks again. Especially if you're only use is the phono stage, depending on your budget, you can obtain a phono stage that will either equal or exceed the performance for little more than the repair bill would be.

As Theo said, your repair bill may be just about as much as buying something new. However, it also may not - you might have someone look at it and give you an estimate? Especially if you like the sound of it.

No, dump it. Repairing vintage electronics is not cost effective, especially since parts are generally not available.

This amp is ancient history DUMP ASAP!!!

Actually, it is from 1977. The nice thing about it is that it has dual power supplies and it is a receiver, which can be a great all in one unit for an extra room.

You didn't say what is wrong with it and it just might be an easy fix. If you like the receiver and it does what you want then you should explore a repair. Take it to a competent repair person and have them diagnose it and give you an estimate. If it is above $100 or so for the repair it might be time to move on. If it is below that, then, you might be able to get a few more years out of it.