Thread: LCD Backlights
View Single Post
  #4   Report Post  
Posted to sci.electronics.repair
Franc Zabkar Franc Zabkar is offline
external usenet poster
 
Posts: 1,569
Default LCD Backlights

On Wed, 19 Mar 2008 20:57:29 +0000, Baron
put finger to keyboard and
composed:

Another thing I noticed was
that the output capacitors, there is two in series for each lamp, seem
to be very small values. They are marked 18J 3Kv. I assume that is
18pf 5% 3000 volts working.


An 18pF capacitor would have an impedance at 100kHz of ...

1/(2.pi.f.C)

= 1/(2 x 3 x 10^5 x 18 x 10^-12)

= 1/(108 x 10^-7)

= 100Kohm

If 100Kohm were in series with the lamp, then the lamp would be
drawing a miniscule amount of current.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.