b wrote:
On May 30, 12:45 pm, Jeroni Paul wrote:

I'm repairing a DTV decoder Saivod DT2012 (chip Cheertek and tuner LG)
that had a swollen capacitor in the power supply. 6 months ago I
already replaced this capacitor with a low ESR high quality 105 deg
replacement but it just lasted 6 months and is swollen again.

The capacitor is EC205 1000uF 16V and is the filter for 5V output in a
switching power supply. Typical design, small transformer, rectifier
diode, first capacitor, inductor and second capacitor with TNY265 as
primary controller chip. The second capacitor remains cold and checks
fine on the ESR meter. The problem is in the first capacitor, I
replaced it again with a new 105 deg type and it works but I notice
the capacitor gets very hot in just 10 minutes.


might be worth checking the current drawn, out of interest.
i've repaired dozens of these sort of boxes, many of which are the
same inside (MX Onda, AXIL, T Boston, Engel....) and using caps rated
at 25v in place of the 16v fitted usually keeps them working.
-B

Also, you may want to check or replace the UF "ULTRA Fast" diode in that
circuit. I found some that developed a leak but not enough to short and
pass some AC through from the switcher.. This can not only heat the
diode but the Cap. A simple test is to perform a thermal test on the
diode.. It should only be warm at best..