Aquos LC-37H4VU - Blinking Red Light

[pentium]

I put this TV which was missing its AVR into service as a DVI computer monitor and for the last week it was working flawlessly until I tried programming the remote (which I know sounds weird).
While programming the Microsoft media remotes the TV was rapidly being turned on and off by accident. Halfway through the second remote it started to turn back on, then the power light went from green to blinking red. No smoke, no nasty noises, no smells.
Did a google search and apparently the all-around indication of a blinking power light is the PSU has a fault. Opening the unit and turning it on I can hear a faint squealing that changes pitch as the front power LED goes on and off.



It will however respond to the power button and remote still so the standby power seems to be okay.
Board is otherwise very clean (wasn't even dusty and the PCB shows no signs of any concerning overheating). All the caps are either KMG or Rubycon ZL. Same seems to apply on the backlight inverters too. I'm assuming the rapid on/off has blown one of the switching transistors, am I correct?

[tom66]

Re: Aquos LC-37H4VU - Blinking Red Light

If there are any fuses apart from the main fuses blown, then the switching transistors have gone, however my bet would be on the output diodes or the main board (there are usually lots of fuses on those.) Or, maybe the EEPROM is corrupt, or the firmware is (which would be a difficult fix.)

[pentium]

Re: Aquos LC-37H4VU - Blinking Red Light

Well the fuses seem alright so far on the power board and inverters, I have no way to see if the EEPROM is corrupt (why would it do that? Power surge?)
If there are any diodes on the lone main board (you meant the video logic board, right?), I'm assuming they are surface mount.


I have not pressed that little green button by the way. I'm too terrified on what it might do.
Where is the best place to start desoldering and testing components? The transistors on the power board that are attached to the four heatsinks? What about for diodes? I totally wanted to spend my weekend doing this.

[pentium]

Re: Aquos LC-37H4VU - Blinking Red Light

Okay, I'm going to need the service manual.
After several days of poking around and googling I found a random note that someone was able get their TV to work by pressing INPUT and VOL - while pressing the master power button. I tried the same and sure enough, the power light went green, the backlight came on and I got a picture.
So, the tv is technically fine but something went out of spec and outside of service mode the screen will prevent the user from using it. The service manual will better tell me what the service mode screens are telling me, unfortunately like all service manuals it's one of those things where everybody has it and you can too....for a premium.

[pentium]

Re: Aquos LC-37H4VU - Blinking Red Light

To respect XKCD's Wisdom of the Ancients, here is the fix I found:

-Put the TV into service mode
-On the first screen, scroll down to "L On Reset = 5" (the number might be different and that might mean other problems)
-Toggle the 5 to 0
-Turn the TV off

When you power it back on the unit should work fine.
If not, go back in and see if "L On Reset" reverted back. If it isn't 0 anymore, something is in a state where resetting the onboard safety will not fix it.

[pentium]

Re: Aquos LC-37H4VU - Blinking Red Light

This thread is old as shit but over the last three years it proceeded to get worse and worse and worse to the point that it just wouldn't fire at all. We also gained a second problem where the screen would fire but you would have an uneven green crawl across the screen left to right.
I traced the source of the problem to an intermittent connection on the Digital board. Pressing down on one of the XILINX chips would make the backlight fire every time (pictured middle left). Not pressing on it or tapping around the digital board meant that the backlight would fail to turn on.
After shimming that specific chip failed to give a reliable fix I decided to reflow the three Xilinx chips, the firmware ship and a half dozen other small SMD IC's. Learning experience time here. I've never reflowed pins this close together. Almost screwed up twice but after tediously repairing one mistake the set was reassembled and now it will always fire the backlight. Yay!



Now, once and a while it will completely kick out and require a power cycle (no diagnostics mode needed) but that might be because I used a new type of flux that wasn't washing off as easily as I wanted and as the set heats up it becomes conductive (bad). I will have to source a much stronger flux cleaning solution besides rubbing alcohol.