Hi guys thought i would post a possible fix for Teac HBBST1 set top box ,the unit just stopped , no power indication on display

This set top box is not a cheep at over $180aud and was out of warranty , with teak offering a repair look at fee over $55aud i thought i take a look at it

The problem was the 1000uf 10v electrolytic cap had failed - shown in the attached pic,
Replace the cap for 16v or 25v 1000uf

The voltage over this cap when not in circuit was measured at 8v and the cap did show a very small amount of "top bulge"
It clear the PCB design allows for larger cap than fitted ( has extra pad holes) , and the supplied cap was voltage underrated for the design use

hope it helps another with same set top box

 

also note after 12 hours use , i have found the range of the IR of the remote vastly improved , clearly production have made a change over the design components used - so typical

 

The first suspects in smp's (or any device) are usually electrolytic capacitors. Even if you find half a dozen fried semiconductors, usually the root cause is high ESR electrolytics.
The life of them is very dependent on operating temperature and manufacturers often cram them next to heatsinks or hot resistors.
As a general rule, if one has failed, change the lot as others are likely to follow and maybe cause more catastrophic damage.
I speak from experience having spent years owning a major service company repairing many thousands of such devices.
It would be advisable that you make a note of all the capacitors on the power supply, then order a complete set from a reputable supplier such as R.S or C.P.C Farnell, high quality 105 deg C not 85 deg C replacements. Most of the ones from E.bay are not of good enough quality and usually cost you more in the long run.

 

normally i would say that is true ,

but in this case the cap in question was in production at 10v , where it is always seeing 8v , where a higher voltage should have been fitted from the start , , else the problem is very likely to happen again regardless of the higher quality caps used

in general , the rule of thumb for higher uF electrolytic would be to use cap voltage rating 2x voltage that cap sees, especially when in the power supply circuit