Pwr suppley Problem

scott93727g wrote in news:5bf45acf-8ab7-461f-b777- snipped-for-privacy@z28g2000prd.googlegroups.com:

Parallel. Now that that's out of the way, you say you're pulling 15A from a 12A transformer for a week. Are you sure everything checks out? Or do you just think it does? How did you test? Did you remember to include the resistors, one low ohm high power resistor for each of the LM338's? If not, one will have taken the strain that should have been shared between them, and thermal shutdown probably prevented outright failure. That might explain the low current you saw. Check your rectifiers too, paralleling those won't share equally between them, you need resistors just as you do with those regulators. If you need more current than the rectifier accepts gracefully, get a bigger rectifier.

Another thing to check out carefully is your mountings, test to see if you have case shorts to the heatsink because the outputs are on the case (I'm assuming you're using TO3 cans) and must not connect together or to ground.