Chi Mei LCD panel inside TV

[Externet]

Hi.
Feels painful to dump it; found a couple of smoked parts -Coil and transistor in a DC-DC upconverter circuit.- Of course they blew up to protect its surface mount fuse nearby on the display panel board (Not the receiver main board)
I know the DC-DC chip takes 5.1V input and upconverts to something higher for the LCD panel marked 'VAA' but cannot find schematics.

After replacing the burned parts, I get 4.3 V at test point VAA but should be much higher... I think

The panel is Chi Mei part # M220Z1-P01 inside a generic Element brand, 22" TV

What is that Vaa voltage supposed to be?

The panel is very similar to this one, the blown surface mount black coil was the one below the third T of "...Touch" at top right.

---> http://x704.net/static-image/Displays/Chi Mei N133i.jpg

 

[(*steve*)]

Can you show us an image of the smoked board?

Are there any capacitors on the high voltage side that might give an indication of the voltage?

Are the smoked parts too damaged to read any of the part numbers?

Is the board simple enough at that point that the circuit could be traced?

 

[davenn]

the section of board you show there on the LCD panel isnt part of the high voltage,
that board has all the digital multiplexing cctry for the pixel driving

the high voltage board is in a different place, where the 1kV odd is generated to supply the fluro tubes

cheers
Dave

 

[Externet]

Hi. Thanks for replying.

Sorry, have no camera, or I would have done it. The circuit is an upconverter to supply LCD circuits, nothing to do with high voltage nor backlighting. Probably around 12-24 Volt out. Packed in about 15mm x 15mm of board area.

No electrolytics, only the typical brown surface mounts with no markings; The coil had a stamped "100", replaced with same, a blown transistor replaced with a generic one.
I traced the circuit and is very similar to the application data of its controller chip FP5138:

http://www.micro-bridge.com/data/Feeling-tech/FP5138 5V TO 15V 3A.pdf ---> L1; Q2 (*)

http://www.feeling-tech.com.tw/km-master/front/bin/ptdetail.phtml?Part=P1-03

Cannot find schematics for the panel, used in several brand TV/monitors, and did not discern from the data sheets what component values determine the output. I would have measured them to find out. My last resource is to make a separate circuit and replace the one on board. But who knows if what caused the failure will then work.

* What I believe is Q2 shorted by either
-being tired or
-the oscillator stopped
and Q1 + Q2 got stuck in conduction, and then fried L1 and itself. Would you agree or see another cause ?

 

[(*steve*)]

Yeah, if L1, Q2 in that circuit have expired then it is almost certainly caused by Q2 being turned on for too long.

The cause could also be a short across Q1 or Q5 going open circuit, or perhaps some unusual behaviour at low voltage (on the 5V rail)

 

[niffcreature]

the section of board you show there on the LCD panel isnt part of the high voltage,
that board has all the digital multiplexing cctry for the pixel driving

the high voltage board is in a different place, where the 1kV odd is generated to supply the fluro tubes

cheers
Dave

interestingly put "digital multiplexing". I have always heard it more in terms of "serialization"

Hi. Thanks for replying.

Sorry, have no camera, or I would have done it. The circuit is an upconverter to supply LCD circuits, nothing to do with high voltage nor backlighting. Probably around 12-24 Volt out. Packed in about 15mm x 15mm of board area.

I dont think youll be able to repair it easily sorry.

The board we are talking about here is not 12-24 volts, at least im pretty sure because the interface here is called LVDS for Low Voltage Differential Signaling.

I was actually pretty surprised to see that picture! what size is this panel? it looks like you could drop that into a laptop pretty easily, whereas usually they're pretty different. Its only a 20 pin interface which is also surprising. not HD is it huh


Anyway, you dont need to build a new board. Thats would be QUITE difficult unless i am mistaken. Also this LVDS is a standardized interface. Here are some good people who can help you out:

http://njytouch.com/lcdcontroller.htm

I think that will get you started. Your panel isnt officially supported, but they sell programmers for their boards, and you can also send it to them if you cant figure out how to decode the signal yourself.
Good luck