Harmon-Kardon built a series of receivers with separate power transformers for each channel. That seemed to be an audible improvement at the time.
The thing is, any receiver or amplifier from that era is going to need work to perform the way it did when new. Controls and switches have to be cleaned, mechanical grounds (often screws holding circuit boards down) have to be sorted out, filter capacitors in the power supplies replaced, and electrolytic capacitors used for coupling and bypass replaced (as well as any tantalum capacitors used as coupling caps- yuk!). Additionally its a good idea to remove the output transistors, clean the heatsinks and reseat them with new heatsink compound. The bias and dc offset controls should be cleaned as well and then adjusted properly. The bearings in the variable capacitors used to tune the FM should be cleaned and the FM given a complete alignment. The unit should be tested for noise- transistors this old can become noisy.
A word to the wise: semiconductor replacements are tricky to find. Most of them are no longer available, although there are likely replacements. But there are plenty of Chinese counterfeits that you can get easily enough on ebay, but quite often they don’t meet spec and may just blow up when installed. A reliable source of parts is East Coast Transistor Parts who has been around for decades:www.kenwoodparts.com/
Do your homework and due diligence when making a purchase like this. Good Luck!
The thing is, any receiver or amplifier from that era is going to need work to perform the way it did when new. Controls and switches have to be cleaned, mechanical grounds (often screws holding circuit boards down) have to be sorted out, filter capacitors in the power supplies replaced, and electrolytic capacitors used for coupling and bypass replaced (as well as any tantalum capacitors used as coupling caps- yuk!). Additionally its a good idea to remove the output transistors, clean the heatsinks and reseat them with new heatsink compound. The bias and dc offset controls should be cleaned as well and then adjusted properly. The bearings in the variable capacitors used to tune the FM should be cleaned and the FM given a complete alignment. The unit should be tested for noise- transistors this old can become noisy.
A word to the wise: semiconductor replacements are tricky to find. Most of them are no longer available, although there are likely replacements. But there are plenty of Chinese counterfeits that you can get easily enough on ebay, but quite often they don’t meet spec and may just blow up when installed. A reliable source of parts is East Coast Transistor Parts who has been around for decades:www.kenwoodparts.com/
Do your homework and due diligence when making a purchase like this. Good Luck!