I've been tinkering with computers for years, mostly Acorn machines for fun but I've never owned or even used an Apple.
One of us! Do I recognise your nick from stardot, perchance?
From what little I've read so far it sounds like it will need re-capping. This is generally frowned upon by the Acorn community but it seems that Apple used some dodgy caps back in the day.
Yes, it will. Apple used physically very small caps and I don't think they're particularly good ones, either. So they leak. It's like the problems that the A4 has in Acorn-land, but over the whole product range. Acorn, at least pre-RiscPC, tended to use physically larger capacitors which I think are more leak-resistant (presumably because they have thicker walls and better seals?)
Where to begin? Take photos, light clean, disassemble and assess?
Yup! In general, this list seems to be in the right order to me.
What are the common problems? Battery leakage, cap failure, anything else?
Battery leakage, cap failure, and their consequences. Battery leakage - Mac boards of the period are far harder to fix than Acorn boards in my experience. That said, you may well be better at this than me, and people do regularly bring back boards that I'd have filed as irredeemably dead. Capacitor damage - the juice is slightly corrosive and can damage traces and especially can get into vias and cause issues. On the IIcx, capacitor juice will often take out the startup circuit, so do not immediately get sad if it won't run.
Recapping - is it worth replacing the lot or are some areas worse than others? Should i change SMD electrolytic for tantalum? (I believe the PCB has both SMD pads and through holes-is this true?)
You need to replace all the surface mount capacitors on the logic board. It's not their electrical characteristics are the problem, it's the gloop they are physically leaking everywhere. In my experience, Macs are remarkably unfussy about precisely what capacitors they have - and in fact Apple only really used a handful of values of SMD electrolytic capacitors throughout the 68k range. It's very much optimised for manufacturing cost.
I personally use tantalums, largely because I bought a lot of them ages ago and I'm still working through them. Tantalum is, of course, a conflict mineral, so you should probably be careful about who you buy from to make sure their supply chain is properly audited. Other people have had luck with solid aluminium can capacitors, and I know of a couple of people using MLCCs even. Others swear by Niobium caps, and they may have a point, they're a bit less incendiary than tantalums if things go wrong. But I don't think it matters overly much. FWIW, I probably wouldn't use tantalums if I were starting again now - I'd probably go for solid polymer can caps instead.
You will generally not damage a cap leaked machine by trying to turn it on to see if it goes. You do not need to be
too careful here.
I assume it won't boot without a HD so what options?
It won't boot, but it will get to a flashing question mark to say there's no boot drive, so you can test that most of the computer is working without a SCSI drive. If you can't get it to a flashing question mark, there's no point in buying an HD-alike until you can.
which of the many SD solutions would you recommend?
First, old SCSI drives are surprisingly robust. I usually leave mine in place until they break and quite a number of my machines have their original drives in still.
This is an amusingly politicised question. Personally, I use a mixture of ZuluSCSIs, MacSDs, and more modern SCSI drives with an adapter from
@max1zzz. All of these are very competent options, with different tradeoffs: ZuluSCSI is probably the most throughput per unit money of the solid-state options, MacSD wins on features (especially CD-ROM emulation and the really cool hardware MIDI synthesiser it provides) and the adaptors for more recent SCSI drives are probably the best value for money overall if you have or can get hold of newer SCSI drives.
I steer very clear of BlueSCSI personally: I got very tired of being abused by the BlueSCSI folks for posting links to datasheets. They are the kind of people who prefer to concentrate on their "vision" rather than the engineering realities of the situation, and the BlueSCSI v1 was consequently electrically a disaster and instead of fixing this with the absolute pennies'-worth of components it would have taken, they chose to just shout at people instead. The v2 is basically a zuluscsi clone with worse PCB layout and support. If you have the patience for that kind of behaviour in your hobby time, it's an option. Personally, I don't, and my life is concretely better for jettisoning that as an option.
Where are the best resources to help breathe life back into this Mac?
A lot of it is probably here!
You'll need a video adapter first of all, though, if you haven't got one with the machine. Apple standardised on a two-row 15-pin D connector for video quite early and kept using it until well into the PowerMac period. So you'll need a mac to VGA adapter. The main purpose of these is to adapt the pinout and to set the monitor detection pins on the Mac side so that the Mac thinks it has a specific type of monitor. Some do not have DIP switches, and they tend to tell the mac that it's got a multisync monitor and lets it deal with that: others have DIP switches that let you set what kind of monitor you want to pretend to have. The best ones for 68k macs have 10 DIP switches, which will let you pretend to the Mac that your monitor is
anything. Be aware it might take some fiddling to find a compromise between the Mac and the monitor.
A decent recapping guide is here:
https://recapamac.com.au/macintosh-iicx/ - I haven't personally recapped a IIcx, but his other recapping guides have been good in my experience.
But yes, before anything else, take the lid off, have a look at the state of the insides, post photos of the board, and see if it already goes in its current state.
