Modifying a 36VAC transformer for 18VDC

I want to modify the 36VAC transformer to give me 18VDC after rectification.

18VAC has an RMS voltage of roughly 12VDC.

So how do I use this fact to calculate the number of secondary turns that I will need to re-wind in order to give m exactly 18VDC?

Do you want to modify 36VAC output transformer to getting 18VDC out?
For calculating the secondary turns you have to provide primary turns and primary voltage.

I think I might have figured it out.

VDC = 1.4 * VAC

There was about 155 turns on the secondary which gave 35VAC.

If I want 18VDC then I need to aim for about 13VAC, 13 * 1.4 = 18.2VDC

So an online calculator tells me that I need about 52 turns to get about 13VAC.

So I have done that, also added a center tap so I can get about 9VDC out of it as well, and re-assembled the laminations.

- - - Updated - - -

It was a discarded christmas lighting transformer - I scored several of them with some 35AC and others 24VAC.

People's trash piles and illegal dump sites are often a gold mine of useful and often expensive electronic components.

We have got looming problems of copper and rare earth metal etc availability and yet most of this stuff ends up in landfill.

It just blows me away how appallingly wasteful our society is.

Well I am doing my bit for recycling at least.

Scored 3 discarded microwave ovens over the last few days - MOTs. I have removed the secondary windings from one of them without damaging anything so I will have a ***** at rewinding the secondary for 12VAC or so at some stage.

I have removed the secondary and primary windings from several others (discarded the laminations). I could build a dozen or so medium tesla coils with the secondary windings from the MOTs.

Using the primary winding wire to build a LED cube at present.