In article , GB
writes
alexander.keys1 wrote:
On Mar 4, 11:09 am, "GB" wrote:
The Natural Philosopher wrote:
Dave Plowman (News) wrote:

Just solder a new 80v cap of almost any flavour over 1000uf across
whats there.

Why would these need to be 80v out of interest? What sort of DC
voltages do these amps typically operate on? I know there's a margin
for peaks, but 80v across a nominal 8 ohm resistance would provide
800w. This is an amp, not a room heater, surely?

80 volts is the *peak* voltage, at the top of the waveform. The
wattage delivered to the speakers depends on the 'RMS' (root-mean-
square, a sort of average), which is 0.707, (for design purposes; it
varies with the waveform) of the peak.

That's still 400w average power.

There are life issues too, derate working voltage to 60 or 70% of spec
and they last 10x longer. Similar issues with temp, 105degC caps last
forever when derated.

Spec'd life at max temp and voltage on an electrolytic is rarely
impressive.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

"fred"

There are life issues too, derate working voltage to 60 or 70% of spec and
they last 10x longer.

** That is complete nonsense.

Electro life is not related to DC operating voltage, unless the rated limit
is exceeded then it is VERY short.


Similar issues with temp, 105degC caps last forever when derated.


** Also complete nonsense - there is little increase in expected life
using 105C types unless the local ambient is over 75C.

Electro lifespan is all about the quality of the airtight seal in the end of
the cap - cos the end of life occurs when most of the electrolyte has
escaped as vapour through an imperfect seal. The rate of loss of electrolyte
is a function of the local ambient temperature and ripple current ( if any)
heating the electro.

105C types can operate at higher temps, that is their only advantage.

Long life electros come in both 85C and 105 C types - all that is different
is the quality of that seal.



...... Phil