I posted some time back about powering up the SX-434 reciever after it
had been unpowered for some years. Using a variac I slowly brought the
power up. Then today I plugged an mp3 player into it and wired up some
speakers and it sounds great! Thanks for the advice folks. BTW, I took
the cover off to look inside for anything amiss. It was all clean
inside, no corrosion, nests, bugs, or bulging caps. There are two
devices that look to me like tubes with metal cans over them. Did this
thing really have a couple tubes in it?

Sony SX-434 (for which I find no references) or Pioneer SX-434?

The Pioneer SX-434 doesn't appear to have any vaccum tubes, according
to the service manual. It does have a couple of large electrolyic
filter capacitors - 3300 microfarads, 25 volts "working volts". These
are located along the left side of the metal chassis, nearer the front
than the back, right in front of the big squarish power transformer.

I'm a trifle disappointed, though... the schematic says that the "no
signal" voltage on those power supply rails is +/- 24 volts. That's
very close to the maximum rating of these caps... not much safety
margin. If you ever have this receiver in for service (or want to
play with it yourself), it might be worth replacing these caps with
3300 (or a bit larger) 35-volt caps, just to make sure they aren't
ever overvoltaged and shorted out by a momentary surge in your
powerline voltage.