Problem with LCD Panel board

[jetadm123]

Re: Problem with LCD Panel board

Suggest you re-measure the voltages of the OZ9936 as you did in post #12.

[bammbammfran]

Re: Problem with LCD Panel board

Hum ?
since you have 5 volts in on 6 and ground on 3, I would think that when the 5 comes into 1 that 4 and 5 should turn on or at least try to.
Bad chinese chip ? or something else is stopping it from turning on ?
see what resistance you have on 4 and 5 to ground ?
verify resistance on 1053 at R104

[mokie]

Re: Problem with LCD Panel board

I have checked pins 4 and 5 and they actually "try" to turn on. They go up to 325mV for a short period of time and then they both go to zero.

Resistance between pin 4 and ground: 11.9 Momhs
Resistance between pin 5 and ground: 12.7 Mohms

R104 is 105.5 komhs

[mokie]

Re: Problem with LCD Panel board

Suggest you re-measure the voltages of the OZ9936 as you did in post #12.

Voltages are the same than post #12

[bammbammfran]

Re: Problem with LCD Panel board

well, I am stumped.
I went though my boards to see if I could find an so8 to compare readings, but most of my controllers are 14 or16 pin. I found an OZ9930Dn with 8 drop-in pin but I can not find a datasheet of that.
325mV is like nothing
Only thing I can think of doing is either removing resistors at R107 and R108 one at a time to see if that chip then puts out 5 volts at 4 and or 5 with them removed
or
If you have a fuse and since it doesn't seem like 4 or 5 are shorted, jump 5 volts to 4 and 5 to bypass the OZ (I think that should fire up the 2 aop609)

[mokie]

Re: Problem with LCD Panel board

oh, this is getting even worse. I have removed R107 and when I turn it on the monitor doesn't do anything. I check with ohmeter and there's continuity between pin 4 and ground. I have removed the OZ and the continutiy persists.

Maybe I should try to link an external inverter which I have over here.

[bammbammfran]

Re: Problem with LCD Panel board

R107 is on pin 5 side so that shouldn't have caused pin 4 to short.
Pin 4 goes pretty much right to the 2 AOP607 so one of them must be shorted

[mokie]

Re: Problem with LCD Panel board

Yes, i have desoldered both mosfets and one of them was shorted. I give up.

Now I'm trying to connect an external inverter to power the lamps. I have located the ON/OFF wire coming from the logic board and now I'm looking for the brighness one. Do you know what range of tension have the brightness control?

[bammbammfran]

Re: Problem with LCD Panel board

the brightness is usually the pin next to the on/off where the two boards connect.
Your pictures do not cover that area from the bottoms so I can not point it out
it also travels to pin 7 of the OZ controller
No idea on your tension question ?

[mokie]

Re: Problem with LCD Panel board

ok, thank you for all your help. I have located the brightnes control (next to the ON/OFF wire). When I change the brightness on the screen I can see how change the voltage on this wire.

But, the external inverter doesn't change the brightness at all. This inverter is like this one http://www.ebay.es/itm/390711004363 . It has 4 pins (V+, ground, ADJ, ON/OFF).

I will have to settle with change the contrast only.

[bammbammfran]

Re: Problem with LCD Panel board

did you check the voltage at the inverter to see if it is going up and down with dim ?
what is the highest and lowest it goes ?

other option
http://www.ebay.com/itm/LCD-Power-Su...-/231235076087

[mokie]

Re: Problem with LCD Panel board

What do you mean by "at the inverter"?. I have checked voltage while connecting the inverter at pin ADJ and the tension is varying but not the brightness.

Maybe it would need more voltage, Right now I'm feeding it with 12v but the Vin says 10-30V

[bammbammfran]

Re: Problem with LCD Panel board

I wanted to know if the voltage right at the inverters pins of the power connector (not the bulbs) was going up and down.
and does it go all the way down to zero and up to 3 volts or do you have different amounts of voltages when you adjust it at the main board

Most of the inverters that I worked on like the one you are using used 12volts, so that should be ok

[mokie]

Re: Problem with LCD Panel board

I wanted to know if the voltage right at the inverters pins of the power connector (not the bulbs) was going up and down.
and does it go all the way down to zero and up to 3 volts or do you have different amounts of voltages when you adjust it at the main board

It goes from 1.1v approximately to 3.3v. It doesn't get to zero.

[bammbammfran]

Re: Problem with LCD Panel board

not all inverters go all the way to zero and some go as high as 5

either way, I would think that since your voltage does go up and down in the common range that the inverter should dim some

you can try to reset the main board settings to factory if you have that option
I had one that resetting it fixed the dimming issues once
you may even have warm / cool / etc user settings options that affect brightness

[SM-Piyes90]

Re: Problem with LCD Panel board

Hi everyone , am interested in this topic , and would like to put my two cents .

Ok so we have here a working CCFLs but no display , witch leads to a lot of theorys but anyways , i se that you are measuring the Inverter IC outputs with a simple DMM witch is not a good idea , since the Inverter IC output is a high frequency square wave switching on/off the two MOSFETS .

So since we are still in the inverter board stage we shloud clear it up first but you can make the same tests for the SMPS power board witch consists of a PWM IC and mosfet/s .

IMO , start first with the power mosfets and check for shorts .
And the best way to make sure the IC is working is checking the VCC pin first (~7 vdc) , and then putting oscilloscope probes at the IC outputs/driver to see if we got a square wave with an amplitudegoing from 5v to 12v.

If all the above tests good then its time to check the HV transformer.

[mokie]

Re: Problem with LCD Panel board

Hi everyone , am interested in this topic , and would like to put my two cents .

Ok so we have here a working CCFLs but no display , witch leads to a lot of theorys but anyways , i se that you are measuring the Inverter IC outputs with a simple DMM witch is not a good idea , since the Inverter IC output is a high frequency square wave switching on/off the two MOSFETS .

So since we are still in the inverter board stage we shloud clear it up first but you can make the same tests for the SMPS power board witch consists of a PWM IC and mosfet/s .

IMO , start first with the power mosfets and check for shorts .
And the best way to make sure the IC is working is checking the VCC pin first (~7 vdc) , and then putting oscilloscope probes at the IC outputs/driver to see if we got a square wave with an amplitudegoing from 5v to 12v.

If all the above tests good then its time to check the HV transformer.

Appreciate your help but now I'm trying to adapt an external inveter that I have. As you can read before, I have located both ON/OFF and brightness control but the brightness doesn't seem to work. Later on I would try to reset the logic board.

[stj]

Re: Problem with LCD Panel board

brightness issue may be a compatability issue.
check the datasheets for the old invertor chip and whatever is on the replacement.
there are 3 types of dimming.
I2c serial
PWM
and variable voltage.

[mokie]

Re: Problem with LCD Panel board

Maybe that's the problem. Now I have the monitor working without brightness control. Thank you all guys.

[SM-Piyes90]

Re: Problem with LCD Panel board

Maybe that's the problem. Now I have the monitor working without brightness control. Thank you all guys.

What IC did you have on the older inverter and also the new one