Sharp LC-52D64U hard to start

[elitegroups]

Greetings all! I have aquired a sharp lc-52d64u from the street and wanted to see if i can bring it back and use in my basement. The set that fails to start up. The tv attempts to power up and you can see the backlight flicker and see a brief picture then it shuts down. It looks like every other ccfl is lit up during the start up. After multiple failed start up attempts, the error code is triggered and you get locked out with power led flashing at 1 second intervals. A hard reset of vol up and chan down and power plug removal clears the error. The thing is that on every successive start up attempt the picture gets brighter and stays on a fraction of a second longer than before then finally the set stays on and the picture is bright and all looks good. The set can then stay on and run for hours. Also, if you turn it off and on again, the back light immediately turns on and doesn't exibit any problems so the problem seems to be related to the ccfl bulbs being hard to start when cold. When you try it the next day same problem. The error code indicates a bad bulb or inverter. The bulbs seem to be integrated into the panel and is non serviceable. Googling seems the concensus is the panel is bad and not worth repairing. Any ideas of what to test? I was reading about bypassing the protection in the ccfl controller?

[budm]

Re: Sharp LC-52D64U hard to start

Please upload good clear pictures so we can see what we are dealing with.

[nomoresonys]

Re: Sharp LC-52D64U hard to start

Take the back off and look it over, it may be an obvious problem such as blown capacitor etc.

[elitegroups]

Re: Sharp LC-52D64U hard to start

Here are some pics of the internals. I didn’t see any bulged caps or any burnt components.

[nomoresonys]

Re: Sharp LC-52D64U hard to start

Shine a flashlight at it look close see if you can see anything on the screen maybe hit menu button, see if there is any text or anything on the screen.

[nomoresonys]

Re: Sharp LC-52D64U hard to start

You will want to be very careful, DEADLY VOLTAGE, on the hot side of power board and the side inverter board, can be over 1000 volts on the inverter board.

[elitegroups]

Re: Sharp LC-52D64U hard to start

The tv works normally with a nice bright picture but when it sits over night and you turn it on the next day it takes at least 7 attempts before the picture comes on and stays on. It behaves like an old car hard to start but runs good after its warmed up. It is easy to restart once it has been on for a while.

[nomoresonys]

Re: Sharp LC-52D64U hard to start

Ok, try heating small section at a time with a hairdryer on power board, see if tv starts up faster, make sure you hit all the capacitors, some of them don't look like obvious capacitors but they have a C in the number beside them.

[elitegroups]

Re: Sharp LC-52D64U hard to start

Good idea, I will try that and report back. I might have to wait till tomorrow.

[Unspun01]

Re: Sharp LC-52D64U hard to start

Hi. I also have this same TV LC-52D64U with very similar problem. TV will not start unless startup backlight protection is bypassed (I can't remember if I pressed VOL+ & CH-, or INPUT & VOL-, or whatever)

Once protection is bypassed, TV will start and run perfectly until it is shut off. Then it may not start again until protection is bypassed once again.

I have ruled out the TCONN and Mainboard and Power Board.

My attention was focused on the lamps or the inverter boards:

INVERTER BOARD 1 RUNTKA327WJZZ (left side top)
INVERTER BOARD 2 RUNTKA328WJZZ (left side bottom) (slave)
INVERTER BOARD 3 RUNTKA329WJZZ (right side top)
INVERTER BOARD 4 RUNTKA330WJZZ (right side bottom) (slave)

Specifically the master inverter boards 1 and 3 with the MOSFET transistors. There are two MOSFET types: 2SK3706 (N-Channel, 12A, 100V) and 2SJ655 (P-Channel, 12A, 100V).

At some point in my troubleshooting I damaged the 327 board by shorting multimeter leads during testing so I just ordered some MOSFETS and replaced a few burned ones but there was also a few shorted zeners and maybe other small smt components so I lost patience and bought a good used 327 board on eBay.

Even after replacing the 327 board, the TV still seemed to have trouble firing up without protection bypass.

*****I think the problem is one or more of the lamps.*****

I have a small home-made high voltage AC probe made from the inverter of an old 17" LCD monitor. I use it to test if a lamp will strike or glow by passing the high voltage lead near the ccfl tube. It doesn't have enough power to light the entire ccfl (it is only for a 17" ccfl) but is pretty useful for testing if a ccfl is good or bad.

The test is this: Bring the HV wire near the ccfl - if it stays dark, the lamp is probably bad, but if it shows a faint pink glow, then the lamp is likely ok.

The problem with this TV is that each lamp glows dimly when the HV lead is brought near the ccfl and dragged along the length of the ccfl which means the CCFLs are ok, and also explains why the TV continues to work for hours so long as the startup backlight protection is bypassed.

I think it is just an over-sensitive protection circuit, but I have no idea how to disable it, or modify it to be less sensitive.

Any ideas?

[elitegroups]

Re: Sharp LC-52D64U hard to start

I was thinking along the same lines, are the bulbs nearing end of life and drawing too much power to start or do they need some extra time to fire? Looking at the datasheet of the ccfl controller oz9928, it says the controller will shut down if it detects excessive voltage, excessive current, or if the ccfl hasn't ignited in the user-defined time, or if a ccfl is broken, or missing.

@ nomoresonys, i put a hair dryer to the power supply hit the power button and the picture flickered on then shut off with power light blinking. I then heated the master inverter board, and the picture came on immediately with no flickering. I will try again from a cold start but what could be the culprit? Dried up capacitors?

[nomoresonys]

Re: Sharp LC-52D64U hard to start

I was thinking along the same lines, are the bulbs nearing end of life and drawing too much power to start or do they need some extra time to fire? Looking at the datasheet of the ccfl controller oz9928, it says the controller will shut down if it detects excessive voltage, excessive current, or if the ccfl hasn't ignited in the user-defined time, or if a ccfl is broken, or missing.

@ nomoresonys, i put a hair dryer to the power supply hit the power button and the picture flickered on then shut off with power light blinking. I then heated the master inverter board, and the picture came on immediately with no flickering. I will try again from a cold start but what could be the culprit? Dried up capacitors?

Could be, could take them off and test them or just replace them and see if that does it.

[Dannyx]

Re: Sharp LC-52D64U hard to start

The OZ CCFL IC is a SOB to bypass the protection on...at least I personally couldn't do it, so I too would be interested how this all works out in the end - always a learning experience here on BC

If the TV works normally from a cold start AFTER hitting the inverter with a hairdrier, could be a bad cap on it...just an educated guess.

[elitegroups]

Re: Sharp LC-52D64U hard to start

The hairdryer trick is working! I heated the master inverter board for about 30 seconds and again the set fired up straight away with no flicker. I'll replace the electrolytics on the board and see. The other thing which i hope isn't happening is heat getting to the bulbs directly behind the inverter board and warming them up, making the board appear to be the problem when it could be the bulb. But probably not as the heat would have to permeate the sheet metal also and it would only be heating a smallm section.

[Dannyx]

Re: Sharp LC-52D64U hard to start

The other thing which i hope isn't happening is heat getting to the bulbs directly behind the inverter board and warming them up, making the board appear to be the problem when it could be the bulb.

Unfortunately, just what I was thinking as well....only one way to find out.

[budm]

Re: Sharp LC-52D64U hard to start

I would replace those low ESR caps on the inverter board first.
BTW, if I remember correctly, those black plastic on the inverter board are the lamp sockets so if you try to pull the boards off the chassis you may ending up breaking the lamps, it's been years since I worked on those inveter board, you can replace the caps without removing the board from the chassis. Those lamp sockets also go bad too.

[Unspun01]

Re: Sharp LC-52D64U hard to start

Thanks BudM.

I didn't try to replace the capacitors and was more focused on the transistors and protection circuits. I'll test with an ESR meter to see if any look bad.

In the mean time, on the OZ9928 IC circuit, what could a person do to de-sensitize the protection feedback?

I had an overly sensitive 47" LCD TV a few years ago that triggered protection for no reason and installing a different size polymer capacitor in the backlight controller circuit solved the problem (but it was suggested to me, and I didn't come up with the fix myself)

Any suggestions?

[elitegroups]

Re: Sharp LC-52D64U hard to start

Back to the drawing board...just replaced all 8 (100v 82uF) electrolytic caps on the master and slave inverter boards with some Rubycons but itdidn't fix it...same flickering. I will try to heat up the large ceramic caps on the master inverter board to eliminate those as the hairdryer trick on the master gets the tv going immediately.

[nomoresonys]

Re: Sharp LC-52D64U hard to start

Maybe test your transformers on inverter, video here checking transformers, it's not a sharp but shows how to test them, in this video it was a bad ccfl tube I believe, he does a nifty little jumper bypass and tv is working again. https://www.youtube.com/watch?v=vNIWtrEHYsc

[elitegroups]

Re: Sharp LC-52D64U hard to start

Thanks, a lot of good info in that video. I touched up all the solder joints of the transformers but didn't help. I was trying to zone in on the individual component that needed to heat up in order for the tv to fire up but I noticed if if heated up the bare sheet metal section next to the master inverter the set was firing up immediately as well. So it seems the hair dryer is heating up the tubes just behind which is the absolute worst case scenario. The set seems like a good candidate for an LED conversion! I saw a video on youtube where a guy converted 42" version but I have to figure out how get to the tubes without destroying the lcd.

https://www.youtube.com/watch?v=jdk-GxU7TU4