Hi Steve, Considering the age of the AC-4 and the good posibility that it has never received any maintenance, you might consider this a good time to recap it. The Heathkit Shop has a kit to do this which has all the parts and instructions. If you are familiar with working on the older gear, replacement should pose no problem for you.
I have no connection with The Heathkit Shop, other than being a satisfied customer. 73, John, W4AWM
