Sansui AU-717

every vintage piece I've had that sounded good, sounded better after a quality refurbishing...can't imagine all those 45 year old caps are in top shape...and like the oil change/spark plug analogy, if a cap goes, it may not go gently...so I would at least have a professional make the decision

I recapped a PS Audio power plant some years ago. Yah sure it worked fine and the caps were not bulging. They were however very dry. In fact, you could shake them and they sounded like baby rattles!!! So this nonsense of "it looks good to me" or "don't fix it if it ain't broken" is never something that I assume. 45 years is good luck on your part, but as someone mentioned here. it might not go quietly in the night and that's that. Hostages could be involved.

When redone, the AU-717 offers an additional level of detail without loss of the essential Sansui character. 

Such a lovely vintage Sansui deserves a health check by a competent EE,  as it is inconceivable that the amplifier will not be running out of bias at the very least.

Likewise miraculous were a good number of lyrics and carbon resisters not to have drifted well out of specification, ergo you will not be experiencing that AU-717 as it was designed to perform.

I generally live by the “if it ain’t broke, don’t fix it” philosophy but suspect that may not apply here. 

@perkri It may seem to work but I guarantee its suffering and not performing to spec. When the filter capacitors in the power supply fail one way they can go is to start to run warm. When this happens they are drawing a bit more current. As the current inches up the power transformer runs warmer too. Eventually this can lead to power transformer failure which can be really painful- something that is cool and interesting has suddenly taken on a lot of the properties of a brick. The transformer can be really pricey if you actually fine one for sale!

They don't always bulge- the plastic sheath around them will sometimes shrink but they might also just look fine. Don't be fooled- they are way too old to be any good.

So if you plan to run this amp get the filter capacitors in the power supply replaced at the very least! Its overdue. Its also not a bad idea to replace electrolytic coupling caps wherever they might occur!