Many enlargers of that period offered lamp position adjustments: the lampholder is at the end of a hollow rod held at the top of the lamp housing, making its height and lateral position adjustable.

Ideally, to make a condenser enlarger function to its full capacity, the light bulb needs to be a point-source type in a clear glass enclosure, and for every magnification, it has to be adjusted so that the image of the filament produced by the condenser is positioned right at the iris position. This is of course a very laborious job so the advent of the opal "Photocresenta" bulb helped to obviate this need somewhat. Still it is a good idea to have it adjusted properly though.

My method to adjust lamp position is not perfect but works reasonably well, and it goes like this:

First I make a dummy enlarging lens barrel out of a cardboard tube, with a scrap of writing paper stretched across the position where the iris is approximately located. First I set up the enlarger to my smallest normal print size and focus it properly. Then I remove the negative, take the lens off and replace it with the dummy lens barrel (Blu-Tack works wonders holding it in position). With the help of a mirror, I can then reach the rod which holds the lamp holder and adjust it so that the image of the light bulb fills the diameter of the dummy barrel. Replacing the dummy lens with the real one, I can thus be certain that it is indeed offering completely even illumination across the negative area.

I use a 1949 model Wasp 4X5 enlarger which I had rebuilt with careful adjustment so as to ensure correct alignment, replacing the modest Wray lens with even an old Componon, and a round of adjustment as described above, I get fully satisfactory result for a very modest outlay.