When I've unscrewed the cable from the balun box... it looked like new so I decided to check the balun (good housekeeping - service all parts).
Well.... the toroid was cooked... blistered paint and a little crack which the photo does not show.
Where do I get a new toroid in a hurry???
Quick look on the "net":
Do I have the materials to make one...? Of course.. The junk box is "full of potential". Little over an hour later I have this on the bench:
The Ugly balun about 6 m of RG58 on 75 mm pipe couple of stainless screws piece of aluminium and SO 239.
This is not "ugly"... it looks good up there.
The SWR is very good (reflected does not move the needle). The amp is happy and I'm happy too.