# reading capacitor value from code printed on it?

Discussion in 'Electronic Basics' started by Bill Christens-Barry, Aug 19, 2004.

1. ### Bill Christens-BarryGuest

I have a circuit board with a capacitor that needs replacing (it got
burned when an adjacent triac went out). The capacitor is a small "bead"
shape, and has the code:

1C4
ME5

printed on it.

anyone help me figure out what its value and max voltage is?

The circuit has another one of these capacitors, and I thought about
pulling it and trying to test its value. My idea is to charge it up to a
known voltage, and time how long it takes to discharge through a known
resistor. My problem is that I don't know what the impedance of the DVM
voltmeter is, and this will influence the discharge rate due to its
parallel resistance. Any ideas on how to approach this? I guess I could
do this experiment twice, using two different known resistor, and back
out the meter resistance. Any better ideas? I don't have easy access to
any good electronics bench equipment, so am looking for simple approach.

BTW, I could post a digital closeup photo of the capacitor if that would
help.

Thanks.

Bill Christens-Barry

2. ### Peter BennettGuest

Any chance that it is actually 104 rather than 1C4 - if so, it may be
an 0.1 uF capacitor - very common value for power supply bypass
capacitors.

--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
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3. ### Geir KlemetsenGuest

Best sugestion:

Second best suggestion:
Build an oscillator that make use of _one_ capacitor. It's important that
you are able to calculate the oscillation frequens for that particular
oscillator. You have an formula f = (r, c). Turn this into
c = (f, r).
Example: http://www.national.com/an/AN/AN-31.pdf page 8. The formula should
be like this:
T = 2 * R1 * C1 * ln( 1 + ( 2*R2/R3 ) ) ( T = 1/f )
Turning the formula to calculate C:
C1 = T / ( 2 * R1 * ln( 1 + ( 2*R2/R3 ) ) )

Hope this helps : )

Geir

4. ### Bill Christens-BarryGuest

Yes, that turned out to be the answer! Careful inspection
showed that some of the paint had chipped off.

Thanks.

5. ### Geir KlemetsenGuest

Best sugestion:

Second best suggestion:
Build an oscillator that make use of _one_ capacitor. It's important that
you are able to calculate the oscillation frequens for that particular
oscillator. You have an formula f = (r, c). Turn this into
c = (f, r).
Example: http://www.national.com/an/AN/AN-31.pdf page 8. The formula should
be like this:
T = 2 * R1 * C1 * ln( 1 + ( 2*R2/R3 ) ) ( T = 1/f )
Turning the formula to calculate C:
C1 = T / ( 2 * R1 * ln( 1 + ( 2*R2/R3 ) ) )

Hope this helps : )

Geir

Btw: This is second time i post this message. It doesn't show up in the
news-group after the first time I posted it.  