4 CCFLs to 2 connectors

[vanbursta]

Can someone help me with some advice please. I have an old PC monitor that was going to be thrown out because there is some screen damage, the panel is a Samsung LTM230HT03, anyway I have a spare panel which is a Samsung LTM230HT01, the only difference is that the 03 version has 2 CCFL connectors and the 01 has 4 CCFL connectors. I thought I would get away with putting 2 of the CCFL lamps in parallel so that I could use all 4 lamps on the 2 connectors on the inverter (2 to each connector), it doesn't work though, I get the 2 seconds to black, I also tried in series, and get the same result. If I connect 2 of the CCFLs everything works fine, and any 2 will work together, however as soon as I connect a third then I'm back to the 2 seconds to black again. Checked all caps and everything is fine, is there any way to modify the circuit so I can use all 4 CCFLs?

A picture of both sides of the power supply / inverter board is below.

https://www.badcaps.net/forum/attach...1&d=1482407958

https://www.badcaps.net/forum/attach...1&d=1482407958

[stj]

Re: 4 CCFLs to 2 connectors

maybe one of the panels only has 2 ccfl's
if it's damaged why not remove the lamps as spares.

[mariushm]

Re: 4 CCFLs to 2 connectors

The boards have circuit which measure the current consumption - if the current is too much , the circuit shuts down.
As cffl tubes age, their current consumption goes up. However, those transformers on the circuit board can only output up to a certain amount of current (the value its designed for plus some margin like 20-40%, to account for aging and different kinds of cffl tubes).
To prevent damage to those high voltage transformers, the board measures the current going to the cffl tubes and kills the circuit if the current is way higher than what the circuit is designed for.

ps. also keep in mind that the monitor may have 4 cffl tubes but as two pairs of cffl tubes, with two cffl tubes in series instead of being independent. This means same current but much higher startup voltages (1500v+ dc to start them)

[vanbursta]

Re: 4 CCFLs to 2 connectors

maybe one of the panels only has 2 ccfl's
if it's damaged why not remove the lamps as spares.

Yes the original panel had 2 CCFLs, but they were both broken, the panel suffered impact damage and that's why it was being disposed of. The new panel has 4 tubes, but they are only half the size or the originals, I thought the inverter might have enough to power them but maybe not.

The panel is working and is backlit, I guess it's half as bright as it should be though (although it seems fine to me).

[vanbursta]

Re: 4 CCFLs to 2 connectors

The boards have circuit which measure the current consumption - if the current is too much , the circuit shuts down.
As cffl tubes age, their current consumption goes up. However, those transformers on the circuit board can only output up to a certain amount of current (the value its designed for plus some margin like 20-40%, to account for aging and different kinds of cffl tubes).
To prevent damage to those high voltage transformers, the board measures the current going to the cffl tubes and kills the circuit if the current is way higher than what the circuit is designed for.

ps. also keep in mind that the monitor may have 4 cffl tubes but as two pairs of cffl tubes, with two cffl tubes in series instead of being independent. This means same current but much higher startup voltages (1500v+ dc to start them)

Yes that makes sense and explains why any 2 will work but 3 or more won't.

Is there any way to put another inverter in circuit and run the Tubes as 2 sets of 2, ie buying another inverter and getting a supply from the existing PSU?

[stj]

Re: 4 CCFLs to 2 connectors

you can get a universal 4tube invertor from china for a few $