Topfield TF4000T STB with bad Samxon GF

[japlytic]

Yesterday, I got a Topfield TF4000T STB from a local junkshop for a song.
Upon opening, I saw a bulging Samxon GF 1000uF 16V unit before the +3.3V inductor.
Replacing this capacitor, along with the rest of the electrolytics (except for the 400V unit) with Nippon Chemi-Con KY units fixed the problem.
The capacitor after the +3.3V inductor was a puny 100uF 25V 85C unit; it was replaced with a 1000uF unit.
Upgrades to the electrolytics were also performed, with the 47uF units being replaced with 100uF units, with C11-C17 being replaced with 470uF units (for the +22V, +17V, +15V, and +8V rails).

Initially, Topfield STBs used Samyoung and Samwha electrolytics (I have a TF5000PVRt with these electrolytics which runs hot, and is still OK after 5 years!), but now use Samxon electrolytics.

Does anyone have any Topfield STBs (satellite, cable or terrestrial) or PVR/DVR units with bad Samxon GF units?

[andyfras]

Re: Topfield TF4000T STB with bad Samxon GF

Topfield PVRs are popular amongst enthusiasts in the UK (models TF5800 & TF5810). I have been fixing PSUs and supplying DIY kits for a couple of years.

Early 5800 models used brown Sam Young capacitors, which failed quite quickly. The 5V cap usually failed first, leading to excessive voltages on other rails, sometimes taking out the HDD and/or mainboard components.

Later models used Samxon capacitors which were better, except the green ones (GF), which failed sooner than the black ones (KM), usually with a domed top. As the green ones were only used for the 3.3V, there was less collateral damage when they failed, but it often lead to severe disk corruption.

The 5810 uses green Samxons in all the main positions and these often fail after about 2 years, especially if ventilation is poor.