I'm not using #5 paper and not buying old paper from e-bay. I get it locally for the e-bay shipping cost.
Thanks for the hint on checking enlarger light and reflections.
My setup is far from ideal.
Got yesterday D5 into the basement and made it works with some improvisation and drilling for missing part which holds M39 lenses on the lens board. And had my first prints from 4x5 this night. They aren't ideal, but stable on FB and RC 8x10
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I need deemer to get longer exposure times for 4x5 negatives. It is 3-7 seconds without it.