To refurbish the MkIIIs:
Get the filter caps replaced. Replace the bias rectifier. Check the resistors- replace any out of spec. Check the tubes and replace as needed. if you want, get some good coupling caps- stay away from paper and oil caps as they can develop electrical leakage that can mess with the bias.
Get the filter caps replaced. Replace the bias rectifier. Check the resistors- replace any out of spec. Check the tubes and replace as needed. if you want, get some good coupling caps- stay away from paper and oil caps as they can develop electrical leakage that can mess with the bias.