On Fri, 11 Jun 2010 11:06:13 -0500 Jim Yanik wrote in
Message id: :

Philip Pemberton wrote in
:

On Thu, 10 Jun 2010 11:52:17 +0000, Philip Pemberton wrote:

then replace
the TEA1522P before wasting time with the opto isolator, shunt
regulator, or other unlikely candidate.

Swapped the 1522. PSU still dead, no output or startup.

Suspects are now the opto, the shunt regulator, and the resistors which
measured high.


did you check the ESR of the electrolytics,particularly those around your
IC? I've seen where high-ESR caps kept switchers from starting.
They loaded the IC supply enough that it would not start.

Huh? From what I've seen, high ESR caps will cause the switcher to shut
down, but from over voltage sensing rather than over loading the outputs.
Shorted caps will do what you say, but an ESR meter is not much good in
those cases. A good low range ohm meter for tracking shorts is best in a
situation like that. Better still if it has 4 wire inputs.