sharp lc32sb24u bulb / inverter problem

[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.

[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.

[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

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

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

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

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

Attached is the page from the manual where they show the bulb connectors are + and - .

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

I will double check when im infront of the TV again, but the wiring diagram clearly shows the transformers (there are 5) have 2 windings a positive and negative winding which each are connected to 1 bulb (there are 10 bulbs) and then on the other end of the bulbs theres a small crude board (which i didnt examine very cloesly, but might connect them to ground. There is deffinetly no way for them to be monitored where they are grounded, if they are grounded at 1 end.

What is your concern? because i tested all the secondary windings quite in detail and they are identical on all 5 transformers. specifically there are 4 pins on each transformer's secondary (2 per winding). And so if i number them as the service manual does with 7 and 8 on 1 windings and 9 and 10 on the other winding, and 8 and 9 are the pins that go to the bulbs, while 7 and 10 are connected by resistors and are what feeds into the monitoring parts.

measuring 9-10 and 7-8 i get 500 ohms, and 7-10 i get 1500 ohms, and 8 - 9 (bulb to bull) i get 2500 ohms (the sum of the other 3). I get that for all 5 transformers.

I could try swapping 2 bulbs and see if the one that doesnt light continue to be in the same place, or moves with the bulb. Also it would be very hard for me to notice a pink issue with the bulb when they only turn on for 2 seconds each time i reset the errors, and with all the other working bulbs around it.

I think ill order a bulb from http://www.ccflwarehouse.com/ as they seem to have cheaper shipping and many more lengths / sizes then lcdparts. Neither lists the start voltages for the bulbs though which doesnt seem a good sign.

[budm]

Re: sharp lc32sb24u bulb / inverter problem

I have never seen the bulb in series connection used in the TV LCD panel, each one is driven by the dedicated winding of the transformer, the the other end of the lamps should return to ground through a sensing network to tell the inverter IC if the lamp is fired up and stays conducting or if it draws too much current so the protection circuits will kick in.
You may want to check the cold side of the lamp assembly.

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

No it didnt really seem to be any worse then the others (they all have a little bit of black near the edges, maybe 3 mm worth or so).

But since they are in series with another bulb and all the other bulbs are working i figured it was pretty likely that it is passing energy, just not starting. So I would assume it has a good connection and is receiving the proper current.

Earlier when i was getting annoyed at the unit i adjusted a rotating switch that had 1 - 0 - 3 marked on it and it was at 0 to begin with, i set it to 0 and could hear a flickering crackle from the center of the light box (approximately where the bab bulb is), then i tried 3 and it was no different then 0)

[budm]

Re: sharp lc32sb24u bulb / inverter problem

You can try lcdparts.net
Does the bulb has any sign of bad indication like blackened ends, pinkish glows?

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

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.

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

On 1 board there is AC comming in it passes through inductors then goes to bridge , dc ouput goes through main dc cap, then dc is given to both the 13v and 5v transformer, and the 13v has a relay in the way.

On the parts board the AC comes in then goes through inducors then a relay, the neutral AC wire is ignored for now, after the relay the hot wire is ran to both AC pins of the bridge rec, the bridge rec then has its outputs run to both sides of the 2 dc caps in series, and their inner pins on the 2 caps in series are run to the AC neutral ... as a side note on this power supply the AC before the relay is seperated off into a manual bridge rec (4 physical diodes in pairs going opposite directions ... ) which leads to the 5v.

What exactly is the advantage of these 2 designs??? The second one seems totaly crazy, to build your own bridge rec out of diodes ...

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

Out of curiosity I did some more testing using the "not working/ untested" board i bought, and it is truely not working , its only outputting 1.2v or so on the 13v rail, the 5v appears to be running correctly at 5v though.

I tested the big caps (2 in series), and get 290v that quickly trickles down to 110v. Also the bridge has only 110v across its dc pins usually. and the AC pins i get almost no reading on, which is odd, but i do get 110v at where the plug attaches to the board.

Im pretty sure the original board i had was a active pfc board (cause of the extra transformer completly in the primary side), but the board i bought for parts and is not working has 2 large dc caps vs 1, and no transformer completely in the primary side. What should i be expecting for voltages on the caps / bridge assuming this model must be a high efficiency model that steps up the AC (there are some transfromers with huge copper wire on the bottom left that i assume are for stepping up the power before it enters the bridge rec. )
What would yall test next on the board with the bad 12v rail?

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

BTW: there are only 6 wires going to that connector i pictured. REG / OSC / BRT are not there (no wires ran to them, although they probably connect to something on the board).

When i measured the err pin it was around 2.7v till the backlight came on then it went to 0v and stays at that even after the set turns off and starts reporting the error code.

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

Well the whole wrench in this damn problem is that the board has to be 100% in place (since the bulbs connect into the sockets on the side of the board.)... So i have no way to test it with the board loose, and the 10 pin IC is on the backside of the board. I guess i could test the err pin on the connector though ... gonna go see what it shows now.

[tom66]

Re: sharp lc32sb24u bulb / inverter problem

Do those error pins, or OFL/OSC show any change in voltage after ~2 secs?

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

Ive attached 3 pictures. The first is a view of the whole back of the board. The largest IC with 3 pins a regulator, the 10 pin is the AC/DC converter IC, and im not sure what the small IC does. The design of this inverter doesnt lend itself to testing very well since all the transformers are in parallel.

There are 2 groups of 2 FETS which provide the 2 AC inputs for the transformers and each group is gated by the AC/DC IC. The FET's appear to convert 13v power to the AC voltage. I have tried testing the AC voltage while the TV is on (for about 5 seconds), but do not get any readings. But the TV does light up, so obviously its an error in how im trying to measure it.

I also included a picture of the connector, because im wondering if theres any way to fool the err pin? (I assume its what reports the error to the main board), Like would cutting the wire work, or does the err pin transmit a steady voltage to the main board to prove everything is working.

[cashkennedy]

Re: sharp lc32sb24u bulb / inverter problem

I received the used / non working similar inverter and it did infact have the same transformers (it appears every sharp for like a year used basically the same mainboard and very similar power supply / inverter layouts.

I realized the bad transformer just had the winding broken off at the pin, so fixed my existing transformer and it tested as 2.68 kohm, which is a tiny bit high but within 4% of the others now. So i didnt really need to buy the other inverter from ebay.

Anyway it didnt work still after fixing that. As a recap after a error reset the screen comes on for 2 seconds and i can see the channel 2 display at top. Then it turns off and flashes a green light once per second (which means inverter problems).

My current question : Im trying to test the DC/AC IC that controls the FET's for the backlight (it might also control the error reporting?). The part number was melted on the one on my existing board (not a good sign), so luckily i had the other board to read the part number off of, and it is BD9883.
http://www.alldatasheet.com/datashee.../BD9883AF.html
Is there any good method to test this IC? I did verify that all the pins went to the parts described and all seem to have good contact and go where they are meant to go.

As a side note, with the other "untested / not working" inverter, it doesnt turn on the backlights and just flashes 2 green lights (some other error)