Relays, Capacitors, and Blown Speakers

OK, so I just picked up a used NAD 2400PE, a 100W circa 1990, because I love the sound of my old 7225PE receiver from the same era. After doing a bit of research on this particular amp, I see that it and its 2000-series brethren were prone to speaker relays going bad. In addition, the amp and its original caps are 20 years old. My question is, when a speaker relay, output, or large cap malfunctions, is the speaker automatically in mortal danger from DC or something else? This particular model has 40,000uF in its supply, BTW. Any input would be much appreciated and help allay my fear of using the amp w/good speakers.
find and read the's here somewhere, the subject of which is caps and cap aging. Lifetime is addressed. Please read that carefully.

Speaker relay? I don't see how that part going South could damage speakers. They just won't turn ON. ...... OTOH, if the relay fails latched ON, you could get a startup pulse of DC to the speakers which could damage them.
Relays, being mechanical, are somewhat failure prone. In a 20 year old piece? If it is socketed, just replace it. Hardwired? ask a tech for cost. I'm honestly not sure how much damage such startup pulse could do to speakers, but it couldn't be good....just how bad?
I have a 7140 that is exhibiting relay problems-just takes a really long time to turn on the speakers.
Had a start-up pulse take out the tweeters on one of my DCM's right after getting an amp out of the shop and spending $300 for all new caps and re-bias etc. However-this particular amp was not equipped with a relay at all.(Pioneer SX-2500)
I was less than pleased.
I don't think this type of relay CAN stay in a "latched-on" status; In my limited understanding it is an electro-magnetic switch that requires voltage to engage contact.
I've seen many cases over the years where the speaker relays internal contacts get dirty/oxidized etc. with the effect being low level noise/hash. cranking the volume up loud or power cycling will sometimes improve the connection for a short time. I've had this with several amps including an old KSA-150. As Magfan states, the relay(s) could also hard fail totally and not engage, or even "stick on". I've never seen these failure modes, but definitely not impossible... with the "stuck on" being the only obvious relay failure mode that could conceivable cause speaker damage.

I've also owned and re-built probably a dozen or so old Marantz 22XX and Heathkit AR-15XX series.

In my case I've never done any "cap-jobs" and have never had any failures. Some people swear by replacing all or as many as possible caps. Obviously if there were reports of a specific component failing, then no doubt.
I think what Magfan maybe referring to, besides a fused-closed set of relay contacts, is the circuit that controls the protection relay's coil can fault during initial system power-up (or is permanently damaged), which is usually delayed until after full system stabalization (several seconds), thus the "click" sound one hears. Same goes for power-down where the relay drops out first to protect speakers while the amp's voltage drains off slowly.

This is a typical relay controling method in all kinds of equipment, usually triggered by IC's which do fail "open" or "latched".

Right you are, Metro.
Their is also a class of part called 'time delay relay' which is internally controlled to enable the circuit a given amount of time after receiving the 'on' command.
These also fail and will sometimes latch in either open or closed conditions.

years ago I had a special set of files used for dressing relay contacts which had stuck or 'fused', as Metro ref's.
Wait, I know this one! "Alex, what are burnishing files?"

...And right you are regarding TDR's.