Interesting chalky substance on the neck board of this CRT. Not the usual caramel-like heated flux debris I’m used to seeing.
@RetroViator That's the residue you get from washing PCBs but not washing them well enough. If I remember rightly it's salts and additives in the flux. If it's gotten that bad then the original manufacturer wasn't a fan of changing out their wash tank.
Safewash, Fluxoff or Fluxclene will remove it if it's a problem.
Edit - deionised or distilled water and dishwasher soap (non foaming) might also work but will need a good rinse after.
@philpem Thanks! That makes sense. The board is also good and sticky.
@RetroViator Definitely saturated wash or rinse tanks then. Sounds like they wanted to save some money by doing the bare minimum - sticky suggests flux residue. It's common to see this on wave soldered boards. Cleaning is a common way of cheaping out.
The industry standard is a 2- or 3-bath set-up where the rinse overflows into the 2nd wash and the 2nd wash overflows into the 1st. For batch work they sometimes use dishwashers!
@philpem thanks for this. i've seen that residue dozens of times over the years, and always was curious about it!
@vga256 no problem! I did the IPC 7711/21B PCB rework course through work some years ago, and that's what the instructor told us it was when we asked. It's one of those things that's known in industry but not necessarily documented formally.
@philpem very cool!
@philpem @RetroViator ahhhhh thank you! I always wondered what that crap was.
@vxo @RetroViator So did I! I ended up doing the IPC7711/21B PCB rework training course through work a few years ago and it came up in the "prep and finish" section. It's one of those things that isn't well documented, at all!
edit: there's a bit more about it here, the industry term is "ionic contamination" - https://prostech.vn/the-nature-of-white-residues-on-pcb-and-how-to-remove-it/
@philpem That’s great information. Thank you. Since it can be corrosive, I’m glad I got it off the board.
@philpem @RetroViator Thank you! This is all absolutely in the very good to know category :)
@philpem @RetroViator love Electrolube Safewash & Fluxclene! Great stuff. Fluxclene being orange-oil based always makes the boards smell nice too!
@ret @RetroViator I can't believe you think Fluxclene smells good... the last time I used it, it gave me a headache. I keep it as the nuclear option for when neat isopropyl fails me.
It's mostly cyclohexane and other hydrocarbon solvents with about 20% isopropyl; the orange oil is a minor component part (see https://docs.rs-online.com/8f7d/0900766b8001ed27.pdf - about 5% max)
@philpem @RetroViator oh, the boards smell nice afterwards. But during cleaning, nope, way too solvent-y!
@ret @RetroViator I can't say I've sniffed a Fluxclene'd board, but you do you! I can't believe you dunk boards in it for what it costs per litre these days 
I keep meaning to get a bottle of Safewash to try in the ultrasonic.
@philpem I tend to just hold the board vertically above the sink and give it a top-to-bottom antistatic scrub with Fluxclene, then rinse with it. Doesn't really use that much.
Safewash, I only use on boards that can get wet (I.e. no RF modules with cans, that sort of stuff). I feel like it might foam too much for ultrasonic cleaners?
@ret interesting! I was looking at Safewash Super as my usual supplier claims the regular Safewash is discontinued. HKW/Electrolube claim it's ideal for ultrasonic cleaners...
@philpem ahhh damn they killed it! https://www.rapidonline.com/electrolube-swa400h-safewash-2000-400ml-87-0730
What the! It was great!
@ret I think Safewash Super might be the replacement - or Rapid stopped stocking it because it wasn't selling well. CPC might have it.