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Testing CCFLs

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OldLes:
The saga continues, but more confusion.
As stated earlier, this inverter board will fire up the two CCFLs which are series connected as in my sketch.
The off load voltage is 8,200 V pp (3,900V rms), falling to 3,100V pp (1,095V rms). The tubes from the Toshiba 23" LCD measure 20" each, so I expect it to light up the 28" tube from a 32" LCD, and the 35" tube from the 42" LCD.
Not so!  Once again, just some excitation at the ends, but no proper illumination. I really can't explain this; I even tried linking two sections in the hope of increasing the output level, as I did with the Samsung inverter earlier, but no luck this time.
Oh well! At least I have two testers for shorter length CCFLs.
The search continues.
Les.

Keith:
Hi Les,

What have you done to overcome the protection circuits?

Keith

OldLes:
Kieth, for the Samsung inverter, see my earlier post. I supplied +12V to the supply pins (10,11 and 12), and  the -12V to pins 1,3,5,6,8 and 9. I then connected the +12v through a 10K resistor to the pin4, which fired up the inverter for about 2 seconds, plenty of time if the CCFL is OK.

For the 23" Toshiba's inverter (LG-Phillips manufacture), I connected it exactly as shown in the sketch I made (LC-230W01-opn_1.pdf  --See earlier) Pressing the push button switch, holding and then releasing  runs the inverter for about 900mS, again enough time for a good CCFL. You will see from the sketch that pin 8 needs to be held at ground, with pin 7 somewhere between 1V and 5V, hence choice of 3V3 zener. The fact that it will fire two 23" CCFLs in series, but NOT a 32" or 42" confuses me.
As somebody else once said, "I will be back"!
Help gratefully accepted.
Les.

Keith:
The reason they dont stay on is because the protection is activating. Download the data sheet for the control chip to find the  protection pins.

Keith

OldLes:
Kieth, sorry, I misunderstood your question.
Problem is I don't have a circuit for the LG-Phillips board. It has six pairs of HV transformers, powering through six connectors, the 12 CCFLs (made from twos in series).
They are divided up into three sections (thus four CCFLs per section) each with a BIT3106, presumably "in control". Any suggestions?
When I first got it working, I had a 3k3 resistor where I now have the 3v3 zener. It then needed the push button pressing, then releasing. The CCFLs would light, and generally STAY on, until I BRIEFLY pressed the push switch again. Maybe playing around with values would help. Possibly using a resistor (4K7??) in parallel with the zener? However, if the CCFL is good, I think the ON time is OK.
Les.

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