After reading about the resurrection of a 575 tracer. I thought I'd ask about my 556 scope.
I've had it for about 15 years now and use it from time to time. And it has worked fine so far. When I first got it, I tested all the tubes replaced a couple weak ones but most were still original and in great shape.
Other than that I've not recapped it or done anything else to it. I also have a number of plugins which all seem to be working well and other than checking tubes and maybe some switch cleaning have done nothing else to those either. And most stuff seems to be in reasonably good calibration, at least close enough for most things I do. I know the main frame is only rated 50 MHz but I can lock and see signals to 100MHz (at greatly reduced amplitude) so it seems very stable.

That in itself is a testament to the build quality of Tek products of the era. The fact that its working so well is part of the reason I've not really messed with anything beyond that so far.
That said I know that at this age I should consider going through it at some point. Of course all the lytics would be suspect at this point. It's been a while since I had the case open but I seem to remember a number of can caps In the power supply area. I imagine that to be a pretty big undertaking to rebuild in itself.
Beyond that are there things specific the 556 that are known problems areas that I should take a look at?
Also any tips that might help making a rebuild easier?
Anything is absolutely avoid messing with that might permanently throw it out of whack?
If I'm going to do this I'd like to do it once and be done for the next 50 years!

I do have the complete factory 556 manual.
And have downloaded all the manuals for all the plugins that I have and recently gotten an extension so I can run any plugin out of the bay so servicing them should be no problem.

I am a BSEE and have extensive experience in tube gear (love tube audio, and no I don't harvest tubes from Tek gear for audio!!!) and also have extensive experience doing calibration of all our equipment at work for decades.

However a 556 is not a Leader scope or a Dynaco ST70. So I value any guidance from the experts here.
Thanks for any helpful info everyone!