Samsung LE22B350F2W tripping off

[tom66]

Re: Samsung LE22B350F2W tripping off

Thanks for the tip tom66

Tried it last night, 1nf 5kv cap across the output of the "unused" inverter. The set still shut down.

Should I perhaps try a higher or lower value? If so, what value would I be safe using that wont cause damage to the inverter (I guess as this is a tandem unit causing damage to the unused side may affect the other)

To confirm the top tube is definitley faulty, I gently opened the panel and powered up the TV. Sure enough, the top tube didnt light.

Jim

Well, it's hard to know without calculating the switching frequency. Do you have a scope? If so, hook it up to the primary (24V!!! NOT CCFL output!!!) and measure the switching frequency. The current and voltage the board provides is written there, so you need to calculate the impedance of the capacitor.

Worked example: Say board provides 1300Vrms at 12mArms. (Made up figures.) It oscillates at 55kHz. 1300V at 12mA gives us 108.3kohms impedance. At 55kHz a capacitor of capacitance C would have impedance 1 / (2 * 3.142 * 55000 * C). Either do the algebra or try random values, I came up with 27pF giving 107.1k which is probably close enough. I figure the 1nF is drawing far too much current and shutting the inverter down.

You may be able to use a resistor... but you'll have to find one capable of dissipating 15.6W which can also withstand 2kV. Not cheap or practical.

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

I had put this set to the back of the cupboard for a while to have a think over how I would repair it. I have decided to go the route of trying to locate a tube for it. Stripped the panel tonight and removed the two tubes, rebuilt the unit back up again and decided to power it up to see what was going on. Sure enough one of the tubes is only lighting for a distance of approx 40mm at either end. The other tube works perfect on both inverter outputs.

Now to find a measuring device

[Shurik406]

Re: Samsung LE22B350F2W tripping off

I have a similar issue. The CCFL tubes light up for around 2 seconds and then shut down. I tried a known working PSU but no difference.

Has anyone managed to source a replacement for these tubes?