On Sat, 14 Apr 2018 18:26:59 +0100, (Roger Hayter)
wrote:

Archibald Tarquin Blenkinsopp wrote:

On Sat, 14 Apr 2018 16:00:49 +0100, "Dave Plowman (News)"
wrote:

Need some replacement reservoir caps for a power amp. Nothing special -
just 10,000uF at 63v. RS have them from about 4 quid to about 50.

Old amp so not PCB mounted - just wires to them and plenty space so not
restricted to an identical part - which isn't made now anyway.

Best make to go for? Is a 50 quid one really worth it?

No.

Go for the cheapest.

In the days before deoxygenated silver topped constant impedance pilot
lights, the only parameters to electrolytics that were of concern were
the inductance and ripple current.

A small additional cap was often added across the biggy to take care
of the first problem and the second parameter was usually stamped on
the case of a reputable cap.

The existing electrolytics probably lost performance for years before
the motor boating set in, I would be willing to bet that until crunch
time, there was little warning.

Personally I would go to Ebay and buy the cheapest, if you have
goldfish, then they could worry about the ripple :-)

If you are into gold bonded speaker cables, green CD restoring pens
and satin lined willy warmers, you may want to read up on reforming
capacitors before soldering your investments in.

AB

ESR may also be important, but not so much in a reservoir capacitor at
50Hz. This may account for some of the range in prices. Also working
temperature.
As I pointed out, it is normally catered for using smaller caps across
the big one.

None inductive electrolytics were available, I think the foil/
insulator was doubled and rolled from the center, these cannot have
been commonly used though, I certainly never, ever ordered one.

The reactance at the frequency of use, wasn't the problem, it was
harmonics and the other garbage that hit VCC and ground that made the
need to decouple using smaller caps necessary.


AB