Substituting electrolytic capacitor.

[Dave.H]

I need to replace a 1.2 uF electrolytic capacitor, and the closest I
can find is 1.0 uF. Is it OK if I install this one?

 

[Roger Dewhurst]

I need to replace a 1.2 uF electrolytic capacitor, and the closest I
can find is 1.0 uF. Is it OK if I install this one?

If you are worried stick another one in parallel to make up the total.

R

 

[Dave.H]

This is probably a stupid question, but what value should the second
capacitor be? The power supply is 240 volts, I can only find a 350
volt electrolytic. I've heard the electrolytics don't like too low a
voltage, would this still work?

 

[Tim Wescott]

This is probably a stupid question, but what value should the second
capacitor be? The power supply is 240 volts, I can only find a 350
volt electrolytic. I've heard the electrolytics don't like too low a
voltage, would this still work?

1/10 the rated voltage may be a problem, but 2/3 is about right for long
life.

Capacitors add in parallel, so a 1uF in parallel with a .2uF makes up
1.2uF.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

 

[Dave.H]

Capacitors add in parallel, so a 1uF in parallel with a .2uF makes up
1.2uF.

I was thinking a .2uF capacitor would be about right. Thanks for the
help, appreciate it!

 

[Dave.H]

Another stupid question, but would I be able to use two .01 capacitors
in parallel with the electrolytic? I can't seem to find any .2 caps.

 

[Daniel Mandic]

Another stupid question, but would I be able to use two .01 capacitors
in parallel with the electrolytic? I can't seem to find any .2 caps.

Hello!


20 times a 0.01 , yes.

2 times a 0.1, off course!



Best regards,

Daniel Mandic

 

[Dave.H]

Hello!

20 times a 0.01 , yes.

2 times a 0.1, off course!

Best regards,

Daniel Mandic

Sorry, I don't understand what you are saying. Please excuse my
almost non existent knowledge of elctronic circuits, I'm still
learning .

 

[Dave.H]

I have tested the original capacitor again, this time disconnected
from the circuit completely, and returned a more accurate reading of
1.248 uF. I think being connected to the circuit last time, was the
reason for the mulitmeter giving me a reading of 91 nF. The capacitor
is of the old metal cased type, made in 1966, installed in the base of
an old electric fan. I'm guessing that since it returned an accurate
reading, I should just leave it.

 

[default]

I need to replace a 1.2 uF electrolytic capacitor, and the closest I
can find is 1.0 uF. Is it OK if I install this one?

Sure. Many electrolytic's are specified at +200% to -20% capacity
(common aluminum types in particular)

The designer should have taking the tolerance in account when the
circuit was designed and allowed for the large variance.

 

[redbelly]

Sorry, I don't understand what you are saying. Please excuse my
almost non existent knowledge of elctronic circuits, I'm still
learning .

He was correcting a typo of yours.

You're looking to add 0.2 uF, or the equivalent, in parallel, yes?
Then you just need a bunch of caps that add up to 0.2 uF, all wired in
parallel.

Two 0.1 uF caps will add up to the necessary 0.2 uF.
Twenty 0.01 uF caps, though a rather silly thing to do, would also add
up to 0.2 uF.

Your suggestion (as typed) was to use two **0.01** uF caps, which
would only add up to 0.02 uF. Not what you want. Most people reading
this are probably assume you meant to say 0.1, and just typed 0.01 by
accident.

Mark

 

[John Larkin]

I need to replace a 1.2 uF electrolytic capacitor, and the closest I
can find is 1.0 uF. Is it OK if I install this one?

The context of your problem isn't clear, but since elec caps have at
best +-20% tolerance, and sometimes a lot worse (like -0, +50%, or
even GMV, guaranteed minimum value) it will probably be OK.

John

 

[Eeyore]

Another stupid question, but would I be able to use two .01 capacitors
in parallel with the electrolytic? I can't seem to find any .2 caps.

Use 0.22

0.2 isn't a standard value (except from some ancient US suppliers).

Graham

 

[Eeyore]

Sure. Many electrolytic's are specified at +200% to -20% capacity
(common aluminum types in particular)

Are you sure you mean +200% ? More like +50% max I'd have thought in the case of
electrolytics.

Graham

 

[Fred Abse]

The power supply is 240 volts

That rang a warning bell.

This wouldn't be a motor start/run capacitor would it?

They're special reversible types for AC use and should only be replaced
with a type characterized for that application.

 

[Fred Abse]

The capacitor is of the old
metal cased type, made in 1966, installed in the base of an old electric
fan.

See my earlier post about motor capacitors. "Regular" electrolytic
capacitors will not do, in fact will probably fail spectacularly, leaving
innards over everything.

At that vintage, it may well be a paper dielectric type, not an
electrolytic.

 

[terryS]

I need to replace a 1.2 uF electrolytic capacitor, and the closest I
can find is 1.0 uF. Is it OK if I install this one?

----------------------------------------------------------------------------------------
Since the original posting does not specify the type of use
we may have been assuming (I certainly did intially) this is an
elctrolytic cap. operating on a DC supply of 240 volts?????
Are we sure it IS an 'electrolytic'????
1.2 mfd seems a small value for an electrolytic. At that size it is
not difficult to use a 'non electrolytic' as long as space is not a
series criterion? I have some old DC capacitors for example that are 4
mfd!
Could the capacitor possibly be an AC rated 'motor start' type
capacitor?
If the input IS 240 volts, RMS alternating, the peak voltage will be
in the region of 340 volts. Even if the capacitor is attached to the
out[put of a rectifier? the peak voltage it will encounter will be in
the same range of voltage?
It really would be best to know what is the application is! If an
incorrectly installed electrolytic exploded it could cost someone
their sight or perhaps skin burns!

 

[default]

Are you sure you mean +200% ? More like +50% max I'd have thought in the case of
electrolytics.

Graham

You're right, wikipedia gives it at -20 +50%

 

[John Fields]

The context of your problem isn't clear, but since elec caps have at
best +-20% tolerance,

 

[John Fields]

Use 0.22

0.2 isn't a standard value (except from some ancient US suppliers).