Baron wrote:

Franc Zabkar wrote:

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

Thanks Franc,
I followed your maths perfectly.

I found a lot of references including the circuit diagram for my
particular monitor backlight inverter.

It seems that 18pf is indeed correct and that there are in fact four
back light tubes each with 18pf in series with it. The tubes need
about 1100 volts + to strike and then run at around 700 volts.

In response to another post, because there are two inverters I swapped
ends and the overheating stays at the same end. There is a 0.22uf 100
volt capacitor across each of the transformer primary which in the case
of one of them gets hot and changes value resulting in the current
limiter shutting them both down.

The bad capacitor rapidly looses value when hot air is blown on it. I
hope that replacing this will effect a cure. I intend replacing both
caps to make sure that I don't have to come back and replace the other
later.

Thanks for the support it's appreciated.

--
Best Regards:
Baron.