Sorry, I thought this thread had gone dormant, so haven't checked in very often...
Looks like you'd placed the positive rail capacitor backwards! The positive terminals of both caps are commoned to the zero volt rail.
I assume you mean my little DIY PCB?
No, that is only for the negative supply, the two caps are in parallel.
I've had a look at it now, and I'm more confused than ever.
There was no wiring error, the dual diode (which seems to have survived) was connected across the outside transformer outputs, just like the original one for the positive supply. Two wires bring it's common anode to the DIY board and the caps -ve, and two more bring the 0v rail to the caps +ve.
The cap was about to blow not because of reversed polarity, but because of over voltage! I measured 57V coming out of the diodes, so tried a 63V cap, which promptly exploded.
Looking on the scope I saw there were peaks of 120V. So I tried a 450v cap which survives - but I'm getting a -120V rail.
I'm currently trying to learn more about the nuances of these things, and while I've only scratched the surface so far, I believe these are, or are related to, "asymmetric half bridge converters". And I'm wondering if the "asymmetric" part has something to do with why my symmetric mirror-imaged addition is not providing symmetric outputs...
Oh, and btw do you happen to know why your YT video comes up as "Your browser can't play this video.". I'm seeing this "error" message more and more frequently in Opera these days. ![Angry >:(](https://www.eevblog.com/forum/Smileys/default/xangry.gif.pagespeed.ic.0w4zhwjvDw.png)
No!?
I had just assumed that the reason I was seeing no views at all, was because the video is unlisted, so that "Anyone with the video link can see this video".
It's working for me in both firefox and chrome (with different google accounts).
And recently had a similar issue with an unlisted video linked from a short that also getting no views, even though the short got hundreds...
I've just made it public, maybe that will help.