[retailer]

I've wound many transformers both mains and output using recycled laminations and did for a while use a program I had written in VB.NET, I now have an Excel spreadsheet that does the same thing but is a bit more customisable. For a hobbyist like me like it is not possible to have a complete range of wire sizes so there is often a compromise that needs to be made when it comes to the design - it needs to be made to fit the wire sizes I have.

In using a recycled core the quality of the lams is a bit of an unknown so I do a test to determine the max and optimum turns per volt for a given core, you can't always go by the original turns per volt - the transformer may have been designed to run close to saturation. Once you pull a few apart you find the current density in the wire varies from around 3A/sqmm to 5 or even 7A/sqmm - those transformers that have come from 40's, 50's and 60's gear are generally around 2A/sqmm

While you do not not have to it is advisable to remove ALL of the old varnish from the lams - using solvent this is a messy and unpleasant job, I have heard you can throw the old transformer into a good fire and retrieve the lams once to fire has cooled, I haven't tried this my self but in theory it should work - the bobbin is destroyed but it is not that hard to make another.

Getting the wire to fit ! I aim for a fill of 75%, I find if my fill calc goes much over 80% then it's almost certain the windings won't fit. I have a homebuilt winder that uses a stepper to drive the wire traverse, I have learnt to live with it's failings and now I've had some practise I can if I need to, wind transformers the 'old' way - no bobbin - paper insulation between each layer.

Good luck with your windings, I'm sure you'll find it rewarding