"Meat Plow" wrote in message
news
On Thu, 19 Oct 2006 13:50:51 +0100, Art Deco Has Frothed:

Hi everyone,

I've been upgrading a simple power supply in a satellite receiver using a
kit provided by a company selling spares.

I've noticed that there's quite a bit of difference between the original
capacitor values and the upgraded replacements provided, for instance

Old New

47uF, 35V 100uF, 35V
2200uF, 10V 2200uF, 16V
330uF, 16V 470uF, 35

etc

My querstion is: do the upgraded capacitors only work together as a set
or can any one of them be replaced with the upgraded value?

Either or.

In the latter case, a follow-up quesion would be how much variation in
capacitor value is permissible (presumably as long as it's higher)?

I always opt for a higher max voltage if available. The capacitive value
depends on what the cap does. Electrolytics usually can be subbed by
higher values maybe 20% higher without side effects.



They are a bit better these days, but the capacitance value tolerance on
electrolytics used to be +80% / -20%. An increased voltage rating, within
reason, is of little consequece, provided the part is still of a suitable
physical size to fit where it has got to go. Going up too far on the
voltage, can alter other characteristics of the cap, such as its ESR, which
may or may not be a problem, depending on the cap's function. For caps used
as filters in switch mode or linear power supplies, an increase in value is
often beneficial to the filtering function, but if you go too far, then the
initial charging current from cold, may prove too much for some prior
component, such as a diode or regulator transistor. As Meaty-boy says, going
up 20% on the nominal value will not present a problem, and the values
supplied in the kit should be just fine.

Arfa