Seeking help reverse engineering laptop screen inverter sans datasheet

Thread Starter

seanspotatobusiness

Joined Sep 17, 2016
190
I have a few inverters from broken laptop screens (Dell Latitude LS model) and there are no datasheets that I can find for the controller IC (3972 OAW). There are only four input pins for the inverter board and I think that it might be possible to figure enough out to connect it to power without breaking it and then experiment to turn it on.

I've found what I believe is the ground pin because it's connected to that big metal area of the board that the screw goes through into the laptop chassis.

I don't know, but I suspect the pink pin is VCC. It's connected to the coils and to a giant SMD-capacitor looking thing which can't be a capacitor because it's two terminals are shorted and that's probably not a fault because it's the same on the other boards. But the pink seems to go backwards through a diode (D2) so maybe it can't be VCC? Also it goes directly to a leg on the IC and I bet that won't run off ~12 V so maybe blue is a better candidate?

The other two pins must be the ON/OFF or STDBY and the DIM pins but I think it will be possible to just apply 3 V to either and see what works?

I think I can apply, like, 12 V to the power pins and different combinations of 3 V and 0 V to the other two, right?

(Of course I will take measures not to shock myself)

 
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ian field

Joined Oct 27, 2012
6,539
Does this image make it any clearer what candidates may be VCC and GND?

The Spanish company HR, which was famous for very reliable flyback EHT transformers, also made CCFL inverters. The vast majority were pattern spares for well known makes - if they ever released data sheets, that would solve your problem.

Its a long time since I last dealt with them, and LED backlights have probably made pattern CCFL inverters unprofitable by now.
 

Thread Starter

seanspotatobusiness

Joined Sep 17, 2016
190
Okay, as I suspected black is GND and pink is VCC (I used 12 V).

Blue is ENABLE and seems to be tied to VCC somewhere so leaving it disconnected will turn the board on by default and yellow is DIM (0 V is max brightness and increasing towards 2 V causes the CCFL to dim and eventually flicker erratically; I'll be tying it to ground).
 
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