I am trying to build a double power supply, a simple one with lm 317 and lm337 - nothing special.
The positive rail works ok, also the negative rail but on negative the minimum voltage is -0.7V instead of -1.25. I used lm 337t p+ , two of them with the same result.
What is happening?
most likely you have it connected wrong. 317 has the pins adj, out, in for a to220, and the 337 has them adj, in, out. Next time check the datasheet first