"Eeyore" wrote in message
...


Terry wrote:

"Arfa Daily" wrote in message
"Eeyore" wrote in message
Arfa Daily wrote:

they have tiny 85 deg caps fitted that are rated about 2 volts above
what they

have to work at

There's nothing wrong with that voltage rating. Why do you think they
have a
working voltage rating ?


We've had this conversation before Graham. As a service engineer, which
you, I think, are not, I can only go by experience. The caps which
regularly fail, are (most) always rated just a couple of volts above
what
they are actually running at. Now I know full well that you believe
this
to be a nonsense, but I'm sure that anyone else on here who is
regularly
involved in actually repairing the stuff, will tell you the same. It
might
be some kind of anomaly in your reckoning, or even not possible to your
mind. That doesn't alter the fact that it is true. It might just be a
physical size versus internal heat issue. I just don't know, but it is
so,
whether you believe it or not.

Other than this, I don't want to get into the discussion, as it's not
what
the thread is about, and the last thing we need is another one
degenerating into a ridiculous flame war, as you get madder and madder,
and all the usual suspects jump in to have a pop at you ...


Does the 2v headway allow for noise spikes. Tants often fail this way.

Firstly you don't get much in the way of 'noise spikes' on a bulk
reservoir
cap.

Secondly, tantalums have an entirely different chemistry which can even
catch
fire or explode.

Lastly, the applied voltage on an electrolytic affects only the leakage
current.
You can actually safely exceed the rated voltage of an electrolytic if you
don't
care especailly about this by at least 10% without causing damage. I have
done
this myself after taking careful advice from the manufacturer's agent when
using
a 63V rated cap at around 69V in an amplifier under 'idle' conditions.
FYI the
tech manager was keen to keep costs low. None of these ever exhibited
early
failure problems.

Graham


Be careful exceeding the voltage rating of capacitors. It may be ok on the
batch
you tested but there are batch to batch variations. Experience has taught me
not
to trust manufacturers agents unless they put it in writing which they never
do of
course. Bulk resevoir caps need a 0.1uf in parallel or there will be noise
due to the inductance
of large caps.

I hope I am not teaching my grandmother 'how to suck eggs' :-)


Regards