Weinmann rims still have fans and most here will disagree with what I am about to say. I had a pair back in the day and never much liked them. They felt slow and dead and collected dirt. Recently another set came through the door with a 1977 date stamp. The welds were plain rough and had been crudely filed. Filed at factory before anodise. The weld was not straight. Huge flat spot plus side to side brake grab. No possibility of getting the rim true and very uneven tension to get them half-true. Both rims were that way. Those rims were not re-used by me. A friend wanted them, really wanted them. When he built them up he had to admit they were as bad as he'd been told. Those were pure creampuff rims, no visible sign a brake pad had been nearby. If you want originality keep them. If you want rims that ride well look elsewhere.

When spoke tension is uneven some spokes work harder than others. Or some spokes work not at all while others are overstressed. The chances of getting even spoke tension without a meter are vanishingly small. Not impossible and I have had demonstrations that proved it. But the guys who can do the trick have built thousands of wheels and started out as naturals. Most who claim they can get even tension with subjective methods are dreaming. Getting even tension on an old rim with built-in defects is entirely not possible. Some old rims are better than others. IMO if you get Weinmann concaves that will build well that is pure dumb luck.