Tabby wrote:
On Mar 3, 11:33 pm, sm_jamieson wrote:

My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?

Also saw this but the lead spacing and layout is wrong:http://parts.digikey.co.uk/1/1/91787...ect-tha-series...

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !

Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.

OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.

Simon.


Electronic equipment is complex in terms of the number of possible
faults. Guessing is a poor repair strategy, especially when it costs
£50 a guess. Lytics normally last many decades, though there have been
some duds on the market causing problems.

The simplest way to test the caps is to measure the ripple on them
with the power on. If you dont have the proper equipment, you can use
a mmultimeter on ac volts setting, connecting it to the big cap via a
small 1uF non-polarised cap (ie polyester, not electrolytic). Once the
meter reading settles down from 80v or so, you should get a steady
reading of the ripple.

Its more likely to be something else than the caps.


It isn't.

Either a bad solder joint to the cap or the cap itself has gone high
resistance..but the classic 'it slowly gets worse' is almost 100% sure
to be the cap.

Easily tested by temporarily connecting something of adequate volatge
rating across it.

Caps are just about the only components that fail gradually and non
catastrophically.

Those and valves/CRT tubes.

Everything else tends to be either so low stress it lasts almost
indefinitely, or so high stress that it goes bang and the set goes dead.