Blown Capacitors (?) in a TV Digital Video Recorder

[Red'n'Black]

One thing surprised me about capacitors when reviewing adverts-
- they are listed as having what looks to me like a quite short life expectancy, ranging between 1000 to 5000 hours depending on make etc...
Our tv recorder is on virtually 24/7, rarely on standby - so even at 5000 hours, that's less than 12 months use before they could fail.
The unit is 15+ years old so I'm not complaining, just seems odd.
Maybe the capacitors power-down more than I'm aware of, independent to the standby function...?

The lifetime rating is at their max temperature - usually 85⁰ or 105⁰. They last a lot longer the cooler they're run. They will all dry out and fail eventually but I have some gear 30+ years old and still working with the original caps. There was a particular problem with stuff made around 2000 - 05 where the electrolyte was made to the wrong recipe and ended up in loads of products.

 

[Ross365]

Electrolytic capacitors have improved hugely over the years in terms of life expectancy and reliability (and performance...and size and cost). Many of the ones found in early transistor radios and hifi equipment fail progessively by just drying out and their capacitance just falls. I changed all the caps in a piece of 1970's electronic test equipment and the 1uF caps just weren't caps at all any more, the 10's weren't much better and most of the larger values had fallen by big percentages. There are lots of ham radio rigs for which you can buy a complete set of new caps as a kit from dealers, which is handy if you want 30 or 40 components.

The issue of these components made during the capacitor plague is all together worse, with the caps bursting.

 

[RonMig]

Hmm...

I recall having, about 15 years ago, a PC monitor (CRT type) which was already about 5 or 6 years old (so bought around yr 2000) which didn't just stop working, it started smoking at the dinner table (how rude ! ).

At the time I was just grateful it hadn't also burst into flames....

I just binned it and switched to a nice new slimline LCD screen, but now I'm thinking...
- it might have been a capacitor or 6 letting go big-style ! ?

I wish I'd opened it up, now...

 

[Ross365]

In really old equipment (from the 1930's-1960's) there are capacitors which have waxed paper as insulation and those too have a finite lifetime. A friend of mine was working on some very old radio set which I think ran off the mains and used valves, but didn't use an isolation transformer. I was in his workshop when he plugged it and something was wrong because one of these paper caps exploded with real force, my ears were really ringing and fragments of paper drifted through the air like snow flakes. He was lucky he didn't have his face close to it when it went. At least the modern electrolytics are constructed so they fail at low pressure .

 

[RonMig]

De-soldering and extracting the original cap pins wasn't fun, and even with that completed, solder reset into the holes (!) so I had to improvise a 1mm "drill" to get holes back in the pcb. Any proper drills I get under 3mm don't seem to last very long
Soldering clearly takes a bit more skill than I have acquired yet, but - I'm ok with the end result (so far, anyway).

So - the new capacitors fitted & soldered in OK (good enough, by my standards )

Reassembled the unit, plugged into TV etc and - it Works!

£5 for components (incl some spares) saved £120+ on a new unit.
Happy Chappie right here !

and yes- I put the cables back exactly where I found them, leaning on that bigger-bent-over-cap, lol

 

[MoreWellie]

Glad it worked but you were a bit lucky

so I had to improvise a 1mm "drill" to get holes back in the pcb.

a lot of modern boards have multiple layers with through hole plating which makes connections to internal layers and drilling one of those could break connections that would stop things working

a solder sucker and iron is the cheapest way to remove solder from holes and sometimes you have to add more solder to get it melting properly for the sucker to work

that said, Result!