Vintage Solid-State Audio Reliability

As with any older product the capacitors dry out after say 15 years if used daily

especially in loudspeakers

Electronics from the late 1960s to 1980s from major manufacturers like Mitsubishi, Marantz, Sansui, Pioneer, etc. are not only very reliable because of build and parts quality, but also because of the state of the art in design which I will explain further below.  That said, tuners and tape decks are not as reliable as amplification product due to their mechanical nature of operation.  The only real issue with vintage electronics is the power amplifier.  If it becomes defective, finding a replacement may be difficult requiring someone with experience and expertise in servicing vintage electronics to either find a new replacement that matches specifications or a used part.  Also, with vintage equipment, bulbs or CAPS may need replacement and the tuner may need alignment.  

The state of the art for circuit board design and manufacturing back then was manual surface mount through hole technology where components are hard wired and soldered.   Components were larger.  Today, printed circuit boards use surface mount technology (solder directly to the board surface) with much smaller components.  Most components are machine mounted, and only a minority are manually mounted.  Repair becomes difficult often requiring mounting new components under a microscope and by someone with keen expertise.   If direct replacement components are not available, matching alternatives becomes more difficult since today’s equipment has software that may be affected.  Often, the whole board may need replacement even if one component is the root cause.  If that model is no longer supported or the manufacturer is out of business, it may be impossible to repair.  Therefore, vintage equipment is easier repair IMHO.   It will be interesting to see, and at my age I will not see it, if today’s designs will be making music 50+ years from now   
 

I have my farther’s Pioneer SX 828 still making music since the 1970s.  Completely original including bulbs   Just occasional contact cleaning.   
 

If you proceed, find a good vintage repair service and have the tuner alignment checked and a general check and cleaning.  It’s worth the effort and cost. 

1960s electronics are not reliable due to failing capacitors.

My main power amplifier is now 41 years old. It is Krell KSA-100Mk2. It had been serviced in 2013, just after I bought it, by Krell authorised service centre in Sydney, Australia. They found no issues, no capacitors to be replaced, even bias was within the specification.  However,  they stated that Krell had an upgrade path for this particular model, which suggested replacement of  6 capacitors to a higher quality, which I opted for. Today, the amp is still going strong, playing beautifully with no sign of any "slowing down"... Even the fans inside are still inaudible from my 4 metres listening distance. Amazing piece of equipment, engineered to perfection. 

The rest of my gear is from around year 2000-2010, so not quite vintage yet, all playing very well without any signs of issues. 

So, I think with vintage audio, it all depends on quality of craftsmanship, manufacturer's philosophy of their purpose for existence etc... And of course - some brands are better than others. So, don't be scared, buy quality equipment and check its condition//functionality before buying. 

Enjoy music, no matter what equipment you use for playback. 

@jimbennet  While the design of contemporary CAPs is more reliable, both vintage or contemporary CAPS are subject to increased ESR and higher DC leakage due to dielectric breakdown, electrolytic leakage, or simply structural fatigue over time. As I posted, the through hole and design and manufacturing technology, and larger component size of vintage boards makes CAP replacement an easier task than the surface mount design and manufacturing technology, and small component size of contemporary boards.  Anyone investing in vintage equipment should have someone with experience and expertise in vintage equipment restoration perform a check and any necessary maintenance prior to normal use.  IMHO, all audiophiles should have CAPS replaced periodically regardless of vintage.  Because I suffer from OCD, when I previously owned big Krell separates that ran hot in Class A, even biased models, I had Krell service and replace CAPs as required every 5-7 years.  Conclusion, it is not just vintage equipment that is subject to CAP degradation over time and CAP replacement should be considered routine maintenance, not a reliability issue.