Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes twice

[DPenhead]

Well, as the title goes, this is my issue. I cannot find anything on the error light as to what it means, but have come to the conclusion after 2 weeks of research and talking with others that it may be that one of the small components (can't remember the exact name) that are on the boards on the back left...the ones that are separate components for each CCFL...has fused, or shorted out, causing a power spike in that component when the TV tries to turn on. I currently believe the main board sends a signal for the power supply module to send power to these components during startup, finds an issue, then reports back to the main board that there is a problem with the power supply board. That board looks perfect, although there is a loud 'click' when it attempts to turn on....I feel that is normal, though it is louder than any other TV I have come across. Could be it is sucking power into the board through a short, which is causing it to be louder than it should be, but that's just a hunch. The video I watched last night about isolating each one of these components separately, measuring the power at startup, isolating the one component that is bad, unsoldering it, and then resoldering a jumper across the missing component also seems to match my issue. If it IS the problem, I am not looking forward to the slightly dim bar across the screen, but at least it will be fixed. Is there anyone with something to add? Do I appear to be on track with the issue? And, what the heck are the error code lights flashing, as to their meaning? Can't find that information ANYWHERE...and yes, I have been to the service manual link. Downloaded the files, two at a time, for 3 days straight. Haven't seen it explained... I also would like a circuit voltage schematic, so that I can know what is supposed to have what power where. It is not on the board anywhere, and it leaves me not having a clue what anything is supposed to have what amount of power running to it. I am a novice at this, so please, no Latin electronics lingo. I learn quick....I think...used to build robots and circuitry from scratch decades ago, but have not worked for long on HDTVs, and haven't even touched a multimeter until 3 days ago in the last 20 years. I have however fixed 3 HDTVs in the last 3 months (capacitor issues), am selling parts on ebay from ones I could not fix, and am trying to get into doing this as some form of income when I am unemployed....which has been for the last 3 months... Please, any help you brilliant-minded fellow geeks can offer is GREATLY appreciated!

Thanks,

Dave P

PS - LOVE your emoticon choices...lol.

[budm]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

Are you sure it is not LC42D62U?
You can try looking for the service manual here:
http://elektrotanya.com/?q=showresul...oria=&kat2=all

Please use the attachment funtion to up load good focused pitures so we can see what you have. The board you are talking about is the backlights inverter board.

[DPenhead]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

Eh..yeah...it is. Missed a number in there.

While attempting to start the TV - The Main backlight inverter board (on back, left side) does have 23.66V running through it, and I can trace the voltage through to most of the board. The two connections with power that run to the top ribbon have 23.61V on both. The two connections with power on the bottom running out to the ribbon on the bottom have 22.09V, and 21.40V to them. (Not sure if this is meaningless or not...seemed odd, especially when compared to the next part) The Slave backlight inverter board on the right side back has a little different voltage for some reason...23.65V to the board, 23.60V on both at the top, 21.41V and 21.95V for the two on the bottom. Also not sure how much of an issue this is, but some, not all, of the transistors on both backlight inverters have power running to some part of them. Seems like all of them should have power running to them, but they don't...again, don't know if this is an issue, or not...just looking into every possible symptom.

BTW, been to that website. I keep downloading my 2 a day limits, and tried to join, but keep missing one question on their entrance exam...lol..argh...still haven't seen anything on there that helps me with this though.

Thank you for your time,

Dave

[tom66]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

21.5~22V is too low for most inverters (rated 24V usually); 23.6V is OK. Re-seat all connectors: a loose connector can have high resistance, causing odd voltage drops.

[DPenhead]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

I've started doing the same thing in my unemployment...normally an archeologist, but times are slow.

I have in the last 2 months turned $50 originally invested into a now working 51" Phillips, a now working Visio 47" (both are my wife's computer monitors), a 42" for sale in a store, about six 40+" ones for sale as parts on ebay, two other fixed ones around the house waiting to resell, some books, some tools, and a multimeter. Not bad. I just got a connection to about 65 broke HDTVs today to do as I please too...so I guess this 'snowball' is beginning to roll downhill. Maybe it will lead somewhere decent. Fascinated with fixing these though...it's fun. What hurts about it all most is not having enough money to buy the 55+ inch LCDs I keep having to pass up for $25-100 that only need $6 in capacitors to fix...argh. Need more money...lol.

Thank you for your input. I was thinking those voltages were too low. I'll trace it back from there in the morning towards the power supply. If the power supply isn't producing almost 25V, then it's probably what? Capacitors? Any idea what might cause the drop in voltage across the board to the ribbons? Or, the difference from top to bottom? Seems like the lower end of those inverter boards are quite a bit different from the top. I just can't imagine why it would be like that. Voltage doesn't go through any components to get there...there are transistors tapping into that voltage along the way though. Anyway, let you know what I find tomorrow...tired.

Dave

[DPenhead]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

I ended up checking anyway... the power supply is only producing 23.65V through all leads I checked in the outgoing plug to the backlight inverters. The orange wire on the far left side is producing 0V, while the orange wire in the 5th slot from the left is producing 23.65V. Aren't both of those supposed to be outputting 25V? All wires on the left half of that plug are hot, while all of the wires on the right half of that plug aren't producing any noticeable current. What does this mean? Where do I look from here?

Dave

[budm]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

Even if the voltage is a little low, I would think you should be able to see if the backlights even flash for seconds, for it to have error feedback, it had to try to start first then reports the feedback back to the main board to tell the processor that there is the problem. So look at the holes on the back of the panel in the dark room to see if you can see the flash at all.
Can we also get good clear pictures of both inverter board so we can read the labels on the connector, we need to check for the BL_ON/INV ON/FF pins, and fuses.

[DPenhead]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

I don't know how close I can get photos for you that you can see...hard enough for me to read them with my magnifying headset. Maybe later I can, but for now possibly these will work. The first picture is of the incoming plug from the power module to the slave backlight inverter on the right side, looking at the back. It has from top to bottom, 5 VBLs (which all have current when you first plug it in of the voltages I mentioned earlier, and also when you hit the power button again after the three tries that the TV attempts to do whatever it's initially doing when I plug it in. Let me make sure you understand this, when you first plug the TV in it starts this sequence of sending current out to the inverter boards...NOT after I plug it in, then hit the power button. Only after the sequence runs it's course do I get to hit the power button to try again...), then there is 5 GRDs, which don't have power, then 2 NCs, which don't either. Next picture is of the Master Power inverter on the back left where it comes in from the power module. These read from top to bottom BLON, I_PWM, E_PWM, then 5 GND slots, and finally 5 VBL slots. The only ones that have power are the 5 VBL slots on this side too. I do not see any lights trying to light when I plug it in, or when I hit the power button a few minutes later when I get the chance again...though to be honest, there are no holes in the back to see such a thing, and it really doesn't look like it from the front. The final picture is of the fuses you wanted to see on the power supply module (I am assuming, it's the only one I can see). Wish the photos were better, but it is the best I can do for now. It is one of those fuses with the little ball in the middle, and doesn't appear to be broken at all...

Is this good enough to answer your questions, or do I still need to try to find a better camera?

Thanks,

Dave

[DPenhead]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

No one has any thoughts on this?

[randtek]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

23.6v is within 2% of 24, is fine. That is not your problem. Your photos really are not adequate, as we cannot read any of the important information on the boards. As far as detailed schematics with voltages etc. - we would all like that. Unfortunately, the manufacturers no longer provide that kind of detail, because they do not intend for the boards to be troubleshot to the component level. If you have downloaded the service manual for this model you can check the meaning of the error codes in it. That information is in the service manual. If you don't find it, I can look it up tomorrow, I don't have access to my records from this computer.

[budm]

Re: Sharp Aquos lc42d6u power and OPC flash once together, then power light flashes t

BLON is the signal from the main board to tell the backlights inverter to turn on, it should be >3v at that pin. So monitor that pin when you hit the TV power switch on and off, it should change state if the main board is sending out the signal to this BLON pin. Read my guides below.