phillips lcd keeps blowing fuse

[TimT]

Re: phillips lcd keeps blowing fuse

ok, I got it all setup and tested 2.9v but was having a hard time making a connection with the pins. burned the wire a little " wire is ok " but noticed voltage drop...so I was thinking BL-SW has 3v so I wired that to PWM-SEL. when I first make contact using BL-SW with PWM-SEL nothing. but as soon as I release the wire I get the flash of light. in other words as soon as I remove 3v from PWN-SEL I get the flash from lamps. don't know if this means anything?

[budm]

Re: phillips lcd keeps blowing fuse

The PWM_SEL is used in this TV, it is a Pulse Width Moduation type signal instead of using analog DC voltage 0-5vdc for controlling the lamp brightness on BL_ADJT pin. Since it is pulse type signal, depend on the kind of meter you have, it may not show anything.
What we can verify is to have MisterD make the brightness adjustment on the TV between minimum and maximum to see if his meter will change from XXX to XXX V.
Brightness control signals either analog or PWM should not turn the lamps off completely. MisterD can also disconnect this the PWM_SEL to see if the lamps will turn off.
We can also look up the LCD panel spec to see what the voltage should be for the inverter board.

[budm]

Re: phillips lcd keeps blowing fuse

It is looking for pulse not steady DC on that PWM pin, so you are pulsing it when attach and remove the voltage.
OK, what you can do is to cut the wire for the PWM_SEL LINE and feed the 3V to the BL_ADJ instead and see if the lamp will stay on.
Most PWM signal will have min 10% pulse width to max of 90% pulse width.

[TimT]

Re: phillips lcd keeps blowing fuse

I removed PWM_SEL and it works is it safe to use the Tv like this? did not feed 3v to BL_ADJ.. just removed PWM_SEL from connector

[budm]

Re: phillips lcd keeps blowing fuse

It just mean that you lamps will be fully on.
Can you get the sticker on the LCD panel so I can look up the spec to find out how this inverter board is setup? It seems to be using active LOW logic. Most TV use analog for controlling lamp brightness.
I also still want to know how MisterD TV reacts at the PWM pin when he makes the backlights adjustment.

[TimT]

Re: phillips lcd keeps blowing fuse

panel is LTA400HM01. So Budm this means the screen will be " full bright " with no way to ajust the brightness

[budm]

Re: phillips lcd keeps blowing fuse

Let me look up the spec of this panel first. I look at the diagram of this TV (supposedly to be the same as Emerson_LC401EM2F per MisterD that I was helping him on), that PWM_SEL is labeled as NU (not used) but it is used on your TV.
Can you tell me if the CN1801 on the power supply board is connected to the other board at CN2106?

[budm]

Re: phillips lcd keeps blowing fuse

OK, I could not download the spec of the panel without sign up at the Chinese web site, but I was able to print out the info on the inverter. The PWM pin 14 is the external dimming control with the typical AC frequency of 150Hz, and no shutdown or flicker at 10% @150Hz. I does not indicate if there is no signal (0V) what will happen.
So at this point, it seems that the main board is not sending to controlling pulses for dimming control of the inverter. We need to look for the correct diagram to troubleshoot the PWM DIMMING circuit on the main board. The panel does not use pin 13 for the Analog lamps brightness adjust.

[Mark369]

Re: phillips lcd keeps blowing fuse

My board keep blowing fuses becasue D1208 was shoted. It's a 200V 1w Zener near
IC1201

[budm]

Re: phillips lcd keeps blowing fuse

OK, I found the micro controller that generate the Dimming signal, it is IC3301 on the main board. I wonder if you can do some kind of factory reset to make this pin working again or not. Found it after looking at page 47 and trace out the signals to page 53.
philips_40pfl3505df7_chassis_pl10_5.pdf

[MisterD]

Re: phillips lcd keeps blowing fuse

It just mean that you lamps will be fully on.
Can you get the sticker on the LCD panel so I can look up the spec to find out how this inverter board is setup? It seems to be using active LOW logic. Most TV use analog for controlling lamp brightness.
I also still want to know how MisterD TV reacts at the PWM pin when he makes the backlights adjustment.

Bud, My 40" Emerson has a cracked screen, you can only make out the picture at about 10 percent of the screen, so I don't think I can adjust backlights because I can't see the functions on the screen.

[MisterD]

Re: phillips lcd keeps blowing fuse

OK, I found the micro controller that generate the Dimming signal, it is IC3301 on the main board. I wonder if you can do some kind of factory reset to make this pin working again or not. Found it after looking at page 47 and trace out the signals to page 53.
philips_40pfl3505df7_chassis_pl10_5.pdf

I wonder if you can do a firmware upgrade to fix that? Here's the Link, if you decide to do it read it carefully as if I remember right you have to download the file to your computer and then extract (unzip) it and then save that to a usb flash drive.

http://www.p4c.philips.com/cgi-bin/d...&slg=en&scy=US

[budm]

Re: phillips lcd keeps blowing fuse

I think the IC may be damaged due to the lighting strike, he needs to find out if the pictures and all the inputs and everything still function, at least he can now see something on the screen. May have to live with it with lamps at full brightness, better than nothing.

[MisterD]

Re: phillips lcd keeps blowing fuse

My board keep blowing fuses becasue D1208 was shoted. It's a 200V 1w Zener near
IC1201

His isn't blowing fuses anymore, he fixed that a while back. now we are working on backlight problems.

[budm]

Re: phillips lcd keeps blowing fuse

I remember helping Mark on that one:
https://www.badcaps.net/forum/showth...t=24444&page=4
But I never know if he was able to get the Zener I recommend for him to use or not, no feedback on that thread if he got it fixed or not. I would like to know the outcome, the thread just stops.

[MisterD]

Re: phillips lcd keeps blowing fuse

I'm not sure if this is the correct mainboard for his Serial number but shopjimmy has 4 of them at only $20 with free shipping.

http://www.shopjimmy.com/pandf-a01pg...-mjc-board.htm

[budm]

Re: phillips lcd keeps blowing fuse

That is just the Jacks board.
So far he replaced the power supply board and the Inverter board, not sure how much money he will want to put into this TV. It is tough when TV got hit by the surge from lightning.
http://www.shopjimmy.com/philips-a01...l-main-cba.htm
http://www.shopjimmy.com/philips-a01...l-main-cba.htm

[tom66]

Re: phillips lcd keeps blowing fuse

PWM-SEL might select between ADIM and PWMDIM or similar.

[TimT]

Re: phillips lcd keeps blowing fuse

Thanks for the help guys!! when I get home I will put Tv back together and see what picture looks like.

[budm]

Re: phillips lcd keeps blowing fuse

Per panel spec, it does not have the ADIM (aNALOG DIMMING), it shows pin 14 as backlights control. I am not sure where the PWM-SEL comes from, it does not have that on the spec.