I have used that very flux In SMD work and it works very well for that purpose. It never would have occurred to me that it could be an issue in point to point work.
I Don't understand Where this, "need extra flux" came from, must be one of those "Internet things"... John
It wasn't until Paul pointed it out that I realised , yeah, 400V across a couple hundred ohms is very different to 4V across the same resistance.
As for the extra flux thing, it came about due to having a lot of trouble with the joints at H2U-H7U. It was in part due to those Keystone strips being a bit oxidised vs the other kind, but in pondering all of this I think I know what actually happened. In an effort to get the diodes in those positions neat and straight (because I wanted to do a 'good job'), I spent a fair bit of time bending the legs just so. What I wasn't thinking about was that the jaunty angle they sit on in the manual is actually pushing the legs into the eyelets with enough force for a good mechanical connection - I traded that away needlessly, for a straight row of diodes. The legs still touched the eyelets, but not well enough to transfer heat sufficient to overcome the oxidation issue. Solder would glob onto the legs of the diodes, and the narrow back of the eyelet, but not the front.
That's not a common problem for PCB and SMD work, where the bulk on internet wisdom is focused, and so most googling around 'how do I get this joint to take' returns results about flux and adding more of it.
It all seems very silly now, but somehow it all appeared perfectly reasonable to me at the time. I suppose this is the downside of doing this stuff in isolation with only the internet for advice, versus what I imagine the old days were like. I imagine back then your mate would pop around, take one look at what you were trying to do, and quickly set you straight. And then you'd repay them with beer.
