sharp lc32sb24u bulb / inverter problem

[budm]

Re: sharp lc32sb24u bulb / inverter problem

When you have two lamps in series, if one is not lit, its impedance will be so high just like an open circuits which is not going to let the current to flow and lights up another lamp in series with it. CCFL has negative resistance, resistance goes down as when the lamp conducts and emits the lights.
The sensing can be done on the hot side also. Most uses the cold side since they will be all tie together then it can sense the total current draw of the lamps.
That will be new to me to have lamps in series and one is lit but not the other one. Will chalk one up in my library for this strange behaving that does not go with the electronics theories. That is why we are here to learn.
I wonder if that 1700v is the strike voltage or running voltage.

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

There are a few samsungs that use U shaped bulbs (which might be a similar design to having 2 bulbs in series. Plus sharp is pretty bizzare with their design choices...

I get what you mean about it being harder to start either bulb if one is burned out. But maybe for the 2 seconds that the other bulb works the inverter is still providing the strike voltage, which has to be enough to overcome the resistance of off bulbs (since the whole point of strike voltage is to overcome them being cold). I have no clue how long the strike voltage is applied though (milliseconds? seconds?)

One website even had for sale stacking U shaped bulbs that each bulb was a different size ... whatever tv maker used that design should be shot though, it was probably toshiba, masters of pointlessly complex designs).

[budm]

Re: sharp lc32sb24u bulb / inverter problem

Most inverter driver IC uses 1.5 second windows to detect if the lamp conducts or not.
The funny thing on your set is that the other lamps stays on and the dead one did not trip the shutdown circuits. Everyone does things in its own ways.

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

You were correct that they are grounded on the other side (I confirmed this by removing the bad bulb, and the one i thought it was in series with still worked.

I then swaped the bulbs and the bulb i moved continued to be bad in its new position, so it looks like its just a bad bulb

Ordered one (3mm x 705mm) from ccfl warehouse, cant wait to get it.

[budm]

Re: sharp lc32sb24u bulb / inverter problem

That is good to know, now that makes sense. Poor Tibimakai, he got the new lamp but he accidentally cracked the screen while putting it back together, poor guy.

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

I got in the bulb, but i ordered the wrong size (3mm thick vs 4 mm thick...). Its hard to measure them because some of the glass is clear around the exterior of the bulb.

The bulb i got didnt hav ethe same connector on the ends as the ones i had, it just had wire on each end. So i had to remove the connectors from the bad bulb (nightmare) and then attach them to the new bulb (nightmare, the metal clip is heatresistant or something so solder wouldnt stick to it)

Finally i found a way to crimp the connectors to the wires on each sid eof the bulbs. Put it in the set and it was quite the wrong color, but the set works and once you put the diffuser / filters on you cant tell at all that its the wrong color.

I didnt know bulb replacement was this much of a pain in the ass...

The correct bulb size was 4mm x 705mm.

[Onlygains]

Re: sharp lc32sb24u bulb / inverter problem

Cash, thanks for the detailed info. I have the same set and I believe the same issue bad bulb. I found additional instruction here:
http://www.fixya.com/support/r105764...del_lc_32sb23u

The instructions from fixit are not for the same set as ours but I've read that it may contain the same guts. I can't find a lamp part# for our model but i'm wondering if the RLMPLA029WJN1 part will work. A couple pictures can be found here:

https://www.donberg.ie/catalogue/ori...pla029wjn.html

I don't have the skill to modify as you did the lamps you purchased. Do you think the above will work?

Also, if you wouldn't mind can you provide some instruction on reaching and replacing. I have the back cover off and see the various boards but am clueless how to best reach the bulbs and how to make certain I put it back together correctly. I've worked on computers for years but this is my first TV repair.

Much thanks in advance and very much appreciate the pictures you shared.

[mmalloy]

Re: sharp lc32sb24u bulb / inverter problem

I was able to bring my set back to life by removing the C7558 capacitor and replacing it with a small jumper wire. This capacitor is on the backside of the inverter board (green side). It is located about an inch below the BD9883 chip. It is an extremely small, surface mount component. This keeps the inverter controller chip from getting the backlight error signal that shuts down the power board and initiates the annoying flashing green power LED issue. You will have to reset the error count after doing this by holding the power and input buttons down for a few seconds until the flashing green light is replaced by a steady red light. Definitely an "out of warranty" repair, but better than junking the whole TV.

[Onlygains]

Re: sharp lc32sb24u bulb / inverter problem

Thank MMalloy.

Any chance you could share a photo of your fix?

For others this link provides additional info although not the exact same model.

http://www.tv.quuq.org/forum/index.p...e;topic=2801.0

In summary:

Managed to sort this one out. The lamp error counter had reached 5 which means the set needed to be started in service mode (hold down input and vol - on tv set whilst applying mains until the letter K appears on the screen, after which press vol - and prog - on tv set to get the service menu). Had no joy doing this though because the ccfl driver IC (BD9883 smd) was going into protection mode and preventing the backlight from operating. To get round this problem I overode the protection by fitting a shorting link across C7558 (smd capacitor) located near the IC. The set would now start in service mode.
Found that there are some test patterns available in the service mode one of which is a grey screen. Selecting this option showed the problem. The area across the centre of the screen was darker than the rest indicating the centre pair of ccfl tubes weren`t working. This chassis uses 10 tubes driven by 5 inverter transformers mounted in line with them, so before embarking on a tedious stripdown I ruled out the possibility of a duff transformer by swopping the centre one with one of the others. No change of course, so I dismantled the unit and checked the tubes and their holders for any visible problems. None were apparent but replacing the tubes cured the problem. Just needed to clear the lamp error and remove the link.

[electronicsurplus]

Re: sharp lc32sb24u bulb / inverter problem

Try this

1) unplug the television and leave unplugged for a few minutes

2)hold volume - and Input at the same time

3)plug the television in while still holding the vol- and input buttons.

This will put the television in service mode and allow you to better test and diagnose the problem.

If you press power off and then on the television may remain working but, for an undetermined amount of time from 5 minutes to forever

This is the method we use to test panels and other boards

Electronic Surplus

[Onlygains]

Re: sharp lc32sb24u bulb / inverter problem

Electronic Surplus, I have already done that. I know what the problem is. It's a bad CCFL bulb. The problem is I can't find an OEM replacement. I am planning on using MMalloys work-around but was hoping for a picture of the fix as I don't know how to replace the capacitor with the small jumper wire or how to fit a shorting link across the C7558 (smd capacitor).

[killian6pk]

Re: sharp lc32sb24u bulb / inverter problem

Electronic Surplus, I have already done that. I know what the problem is. It's a bad CCFL bulb. The problem is I can't find an OEM replacement. I am planning on using MMalloys work-around but was hoping for a picture of the fix as I don't know how to replace the capacitor with the small jumper wire or how to fit a shorting link across the C7558 (smd capacitor).

Did you look at this link, which was supplied earlier in the discussion @ post #27? Jumping anything with a wire is dangerous especially if you don't know what you are doing.

https://www.donberg.ie/catalogue/ori...pla029wjn.html

[Onlygains]

Re: sharp lc32sb24u bulb / inverter problem

LOL, not only did I see it, I was the one who posted it!

Problem is it's for a different model and I'm not certain it will fit.

[Onlygains]

Re: sharp lc32sb24u bulb / inverter problem

Just to close this out... I can confirm that part # RLMPLA029WJN1 is correct and works. I ordered from partstore.com $22 shipped. The fix was incredibly easy. The instructions from the fixya link I shared in post #27 was spot on. Thanks to all and especially Allen Bennett at fixya for the part # and perfect instructions. TV is now working flawlessly.

A lot of fun and my first TV repair. Now on to the Samsung 46" with bad capacitors.

[walking]

Re: sharp lc32sb24u bulb / inverter problem

To confirm the confirmation-Just did this repair also on a dumpster tv..1 sec blink.....

Lamp size: just for my curiosity, 3.4x705mm (glass only measured per ccfl mfg tutorial) I imagin 4mm might fit. There is some play in the length at the ends in original lamps, around 5mm total so a tiny bit longer would still fit. Ends are like a .250" glass fuse set-up.

Replaced 6 bulbs for $18. From Sharp LC32sb23u(not 24u) found on C/L as non working.

$18 invested and now have nice tv for my spare room.

I have 3 bulbs, good LCD screen, diffusers, and mainboard leftover if someone needs them. SMPS was shot (commercial power transformer strike), Old lady said it was only 15 months old when it was keeled.

Also, you can do a white screen input and see bad lamps before taking it apart.

Pics below of bad and good lamps.

[Lrdsatyr8]

Re: sharp lc32sb24u bulb / inverter problem

Hey all... I just picked up a LC32SB24U set from teh junk yard and found this forum and have been trying several of the suggestions... but here's what's been happening. When i first got the set, I plugged the power cord into the wall and turned it on. I got a descent display for anywhere from 5 to 12 seconds and then the set would shut off by itself and the power light would flash green once a second. I tried the VOL- and INPUT button to reset but no luck... So I figured like so many here have stated I probably have a bad bulb (still waiting for one to arrival by mail). While i'm waiting, I figured i would try to jump the capacitor at C7558 (Nasty little bugger to find... almost in the middle of the board) on the power board and in so doing I may have jumped the connection right next to it (would love a closeup photo of that area to see for sure). I tried the set again and still the same problem. I found that if I changed the imput channel to like INPUT4 with a black screen I could access to tv menu. So I brought it up and found the option to update the firmware. Then I got the bright idea to check for updates from the sharp site. I copied the file from the Sharp site to a flash drive and plugged it in. Turned the set back on and navigated thru the menus and began the update proceedure. Everything seemed to be going fine. The set recycled off and then i tried turning it on again. But this time, nothing. Not even a flicker of life on the screen. It didn't even try to turn the screen on. The power light didn't blink at all. However now i get something new. On the back of the main board in the middle, a small light will begin to flash on and off. So what am I doing wrong... and will the blub replacement fix the issue when it comes? Any help would be appreciated!

[Monkeyflowz]

Re: sharp lc32sb24u bulb / inverter problem

To confirm the confirmation-Just did this repair also on a dumpster tv..1 sec blink.....

Lamp size: just for my curiosity, 3.4x705mm (glass only measured per ccfl mfg tutorial) I imagin 4mm might fit. There is some play in the length at the ends in original lamps, around 5mm total so a tiny bit longer would still fit. Ends are like a .250" glass fuse set-up.

Replaced 6 bulbs for $18. From Sharp LC32sb23u(not 24u) found on C/L as non working.

$18 invested and now have nice tv for my spare room.

I have 3 bulbs, good LCD screen, diffusers, and mainboard leftover if someone needs them. SMPS was shot (commercial power transformer strike), Old lady said it was only 15 months old when it was keeled.

Also, you can do a white screen input and see bad lamps before taking it apart.

Pics below of bad and good lamps.

sorry for bring the thread back,where did you buy these bulbs from? i need at least 3

[TopFuel]

Re: sharp lc32sb24u bulb / inverter problem

Hey Monkeyflows I could use one of those bulbs.

What do u want for one?

topfuel388@gmail.com

[Levardw]

Re: sharp lc32sb24u bulb / inverter problem

I would like to purchase a bulb

[freakytiki4u]

Re: sharp lc32sb24u bulb / inverter problem

Just wondering if you ever found the part# for these bulbs? If you still need it, the part# is RLMPLA029WJN1 (old thread I know, but ya know lol)

Well, i officialy wasted a bunch of time.

Note to self: never forget to return to the normal error checking path >

if you have a 2 second to black
1) check inverter transformers
2) check bulbs


... once i fixed the transformer that i had damaged when testing i spend 2 days testing every component on the board ... when all i needed to do was check the bulbs. Sure enough 1 of them is bad. And since theres 2 bulbs in a row for each transformer, i can be certain its just the bulb and not the transformer.


So where do i order bulbs? the service manual luckily gives a list of all the stats it needs ... 1700v, 150hz or something,

Oh and additionally, i will give sharp credit for this being an awesome frame design for the screen. The lcd is attached to the outer metal frame, so you dont have to worry about the loose floppy screen cracking, its like taking the lid of a jar, it fits perfectly snugly over the light box.