[sdiy] Linear PSU Power Sequencing Issue

[ackolonges fds]

Hi All,

Since everyone's talking about power supplies, I thought I might mention a power supply issue I've been having - maybe one of you has had (and solved?) this issue before.

Basically I've been building some straightforward linear power supplies for my modular system with 1A +12V,-12V and +5V (derived from the +12V line) outputs. They are using 12V toroidal transformers, going into custom PCBs with plenty of bulk and localized bypassing, a bunch of diodes, 7812s, 7912s, and 7805s, similar to the power supply on the MFOS website among others.

The issue is that sometimes when I power up a unit with modules plugged in, the +12V rail does not power up properly (the indicator LED does not light), but if I switch the power off for a short time and back on before the caps have discharged, the +12V rails powers up fine.

Has anyone else had this type of (power sequencing?) problem before, and if so, how did you solve it? I couldn't find any information about this in the datasheet, and tried regulators from a number of different manufacturers to no avail. It also seems to happen at certain loads (not necessarily high loads), and not at others.

Thanks a lot for any advice or ideas you may have!
Jason
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20191031/68fe6788/attachment.htm>