Samsung LE22B350F2W tripping off

[bbjunkie]

Bought a 22" Samsung off eBay a few days ago, was itching to get another tv to work on and my patience got the better of me.

Symptoms are.... switching on from STBY causes the set to power up with the samsung tone, then the LCD comes on and it shows a good snowy picture with graphics stating it's on channel 1. With that, it switches off.


The instant I screwed the first screw out I had a bad feeling. It was loose.

Should have known better!

Sure enough, removed the PSU board (labelled ip-55145t) I could see the board was populated with some new caps, and whoever fitted them must have been using an arc-welder, the soldering was terrible.

I thought ok I'll start at the beginning as I don't know the state of these caps, so I removed all and tested ESR was 0.0 Ohms - 0.2 Ohms on the large ones, 2.9 Ohms on the little 4.7uf

All measured fine for capacitance, cant recall now the figures but they were within 5% or less

Quickly for the sake of it while I was there I took a quick run over the diodes to check for shorts, none found.

Voltage checks taken during the power up procedure (See connector in photo below)

Pin1 4.4mv in standby, goes to 12.7mv then up to 10.53V then quickly down to 4.68V
Pin2 41mv in standby, goes to .799V on switch on
Pin3 gnd
Pin4 gnd
Pin5 gnd
Pin6 -4mV
Pin7 -4mV
Pin8 NC
Pin9 2.195v jumps then to 2.987v before switching off

Measurements with the main board disconnected are wildly different, I guess because there is no load things are all over the place, none of the voltages are stable.

1 -5v
2 85mv
3 gnd
4 gnd
5 -5v (yes, this is labelled as GND on the PCB legend)
6 -5v
7 -5v
8 9v
9 -5v

I can't unplug the inverter as it is part of the main PCB I have however tried disconnecting the CCFLs and it is exactly the same.

I have a feeling this may be a tricky one, as it looks like someone has been here before me and it has beaten them.

I've been all over the place with this, not really taking a structured approach but at the moment i'm grasping at straws.

Any feedback welcome.

Am off to have a look at the service manual and training manual to see if I can get any tips.

Apologies for pics, new camera coming tomorrow hopefully.

Jim

[tom66]

Re: Samsung LE22B350F2W tripping off

Rubycons are good caps but they could be fakes.

Samyoung are "essentially" Nippon Chemicon but they are made in Korea, so no idea if they are as good as Chemicon. I have found one or two failed ones, but I've found failed Chemicon caps too.

Back to the original problem: It's likely bad CCFLs, transformer or caps. You can test the CCFLs this way:

- unplug all CCFLs except top one
- turn on does screen light (even a bit?)
- repeat for each CCFL

This will also find a bad transformer or bad cabling if you move one CCFL between transformer outputs.

If the test finds all to be inconclusive it could be a bad startup cap but these usually don't give more than 0.1 seconds of operation when they go bad. Suspect inverter as it lasts for 1 second.

Also check for cold joints on the soldering... if it sounds as bad as it is then you could have a cracked joint. Rework it and use leaded solder, if possible.

I generally don't buy anything anyone has had their paws on before. I've been lucky: not one of the 18 things I've fixed has had a repair made except one plasma but it was professionally done and well soldered (Just a resistor on the primary side. I knew it had been replaced because the manufacturer was different.)

By the way, how much did you pay for it? A new 24" LCD from a noname brand sells for about £130; a name brand 24" LCD would be closer to £170. I generally only pay 20% of the expected final sale price as there's a lot of risk that I won't be able to fix it and it might take me a lot of time.

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

Thanks for the quick response tom66,

Can't connect one CCFL up easily, the connectors are hardwired to the PSU. I will need to make a couple of cables up with spade connectors (will pick those up tomorrow)

There was no mention in the listing that this had been meddled with, or I would have stayed clear.

Will update tomorrow when I have some spade terminals.

[retiredcaps]

Re: Samsung LE22B350F2W tripping off

Measurements with the main board disconnected are wildly different, I guess because there is no load things are all over the place, none of the voltages are stable.

1 -5v
2 85mv
3 gnd
4 gnd
5 -5v (yes, this is labelled as GND on the PCB legend)
6 -5v
7 -5v
8 9v
9 -5v

Do you have your probes reversed to get the negative readings? Or is that your way of saying 5V, but you are just using a hyphen to separate from the pin number?

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

No, I had to check twice, I was confused too. -5v like minus five volts DC WRT Ground

Black lead on chassis.

[retiredcaps]

Re: Samsung LE22B350F2W tripping off

Black lead on chassis.

Can you humor me and redo the DC voltage measurements with the black probe on the ground screw circled in red?

It could be nothing, but I'm always suspicious when I see negative readings.

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

Am off to have a look at the service manual and training manual to see if I can get any tips.

No luck on a service manual, found a training manual for a B350 but there are differences, the PSU is totally different

[Scenic]

Re: Samsung LE22B350F2W tripping off

found the service manual for the US version. LA(merica)22B350F2 instead of LE(urope)22B350F2



The constant restarting sounds much like the Samsung LCD TV EEPROM problem (24C256B on mainboard). If you can't find anything wrong with the PSU/Inverter board, I'd try that..

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

found the service manual for the US version. LA(merica)22B350F2 instead of LE(urope)22B350F2



The constant restarting sounds much like the Samsung LCD TV EEPROM problem (24C256B on mainboard). If you can't find anything wrong with the PSU/Inverter board, I'd try that..

Thanks for all the useful info, will the TV reprogram the eeprom if it is cleared, or do I need to find an eeprom file and reprogram it? (think I have a programmer that would do it if I can get my hands on the file)

[tom66]

Re: Samsung LE22B350F2W tripping off

Most Samsungs will boot from an erased EEPROM but only in service mode, do you have the remote control?

Once erased, turn TV off then press mute-menu-power, you should get the service screen, navigate to factory reset, then power cycle the TV.

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

Yes I have the remote. Next question, im sure you are expecting this....

Can I erase the eeprom without desoldering it? (I can desolder it and erase in my programmer, but i'd prefer not to have the hassle of doing so if I can get around it)

I've read shorting pin 5 and 6 on other models will reset them, but im not sure if they use the same eeprom (AT24c256)

On the 24c256A this would be shorting SCL and SDA together. Does this sound right?

[tom66]

Re: Samsung LE22B350F2W tripping off

Yes I have the remote. Next question, im sure you are expecting this....

Can I erase the eeprom without desoldering it? (I can desolder it and erase in my programmer, but i'd prefer not to have the hassle of doing so if I can get around it)

I've read shorting pin 5 and 6 on other models will reset them, but im not sure if they use the same eeprom (AT24c256)

On the 24c256A this would be shorting SCL and SDA together. Does this sound right?

Depends, with most shorting EEPROM is enough. But problem is almost certainly not EEPROM.

Try plugging in a source with sound, and seeing if sound continues with no picture. It could be 2 secs to black.

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

I had discounted 2 secs to black due to the PSU voltage measurements. I will try plugging a source in tomorrow though and see what happens.

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

Try plugging in a source with sound, and seeing if sound continues with no picture. It could be 2 secs to black.

You couldn't be more right - It certainly is 2 secs to black! Don't know why I didnt think of this before now.

No source to hand this evening when I came out to the workshop so I decided to try another way.

When the TV came on it stayed on long enough to see the channel number. It was on ch1. I pressed ch up button twice and cycled the power again. Sure enough next time it came on it was on ch3. (I'm going to get a source connected before going any further though)

So, jury rigged the bottom CCFL to the psu with the psu on the bench and the same problem was there.
Changed the wires from the bottom CCFL to the top one, powered up.. nothing.

Changed the wires onto the other output on the PSU and performed the same test, again the top CCFL failed to light the screen.

So, with the bottom CCFL wired up and the psu output for the top one wired to another tv (to load the psu) I managed to get it to power up for approx. 10 seconds before going black (previously it was only 1 at most)

I assume because I can see the picture on the whole screen with the bottom only ccfl lit that the same would occur with the top only lit? Therefore proving the top one is faulty?

I guess this is going to be a big job changing it.

[tom66]

Re: Samsung LE22B350F2W tripping off

You couldn't be more right - It certainly is 2 secs to black! Don't know why I didnt think of this before now.

No source to hand this evening when I came out to the workshop so I decided to try another way.

When the TV came on it stayed on long enough to see the channel number. It was on ch1. I pressed ch up button twice and cycled the power again. Sure enough next time it came on it was on ch3. (I'm going to get a source connected before going any further though)

So, jury rigged the bottom CCFL to the psu with the psu on the bench and the same problem was there.
Changed the wires from the bottom CCFL to the top one, powered up.. nothing.

Changed the wires onto the other output on the PSU and performed the same test, again the top CCFL failed to light the screen.

So, with the bottom CCFL wired up and the psu output for the top one wired to another tv (to load the psu) I managed to get it to power up for approx. 10 seconds before going black (previously it was only 1 at most)

I assume because I can see the picture on the whole screen with the bottom only ccfl lit that the same would occur with the top only lit? Therefore proving the top one is faulty?

I guess this is going to be a big job changing it.

The CCFL might be failed, but it's not clear from your post: Did you try running the top CCFL on the bottom transformer? (Or was that when you ran it with the other TV's CCFL, for load?)

There is another possibility and that is the wiring to the CCFLs; is there any at all? If so, check for breaks, damage etc. Listen VERY carefully for a sound of crackling possibly from arcing.

Also, I thought a 22" monitor would use more than two CCFLs? A 32" I had (broken screen) came with a grand total of 14 CCFLs. A 26" I had came with 8 CCFLs. So it would be surprising to me if that monitor uses just two. I'd expect at least 4, if not 6 or 8.

If the a CCFL is failed, it's not too difficult to replace it, although you have to disassemble the panel.

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

Ok, forgive my wooly explanation in my last post! Yes, I tried both tubes on both outputs (it's a single transformer on the board and the output is split before the connectors. Now is a good time to test my new (to me) camera. Photos coming right up..

I opened the panel to have a look in (not fully, dont want to get dust or dirt in) and there is two tubes, they are a U shape only they run horizontal. So in effect there is 4 horizontal tubes.

I have a feeling they are directly connected to the terminals that the pcb connects to. There is no wire visible between the pcb and the tubes.

Next thing would be to get a price to see if this is even worth doing. I know the guys stateside use ccflwarehouse - is there anywhere this side of the pond? What am I looking for?

The panel p/no is T216ha01-db however a google search isnt throwing up much. Perhaps I'm not using the correct terms, I have tried:

t216ha01-db backlight
t216ha01-db ccfl
t216ha01-db replacement backlight

etc etc

[tom66]

Re: Samsung LE22B350F2W tripping off

The closest I could find is this: http://www.ebay.co.uk/itm/Samsung-24...item2a12380f0b

But it's very expensive (qty 6) and it's for a 24", so probably won't fit.

You could try an LED conversion .

I'm being serious, it would probably cost much less than new CCFLs and make for a far nicer monitor.

Trouble is, after doing that, you won't want to get rid of it. I've still got my pride and joy 15" LCD with LED backlight that I made. https://www.badcaps.net/forum/showth...highlight=dell

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

Nice mod! If i could get the inverter to keep running on one tube it would be fine as the picture is perfect like that.

Failing that I can see a weekend project on the horizon!

[tom66]

Re: Samsung LE22B350F2W tripping off

Nice mod! If i could get the inverter to keep running on one tube it would be fine as the picture is perfect like that.

Failing that I can see a weekend project on the horizon!

Some people here report a capacitor can be a substitute CCFL, around 1nF/5kV.

[bbjunkie]

Re: Samsung LE22B350F2W tripping off

Thanks for the tip tom66

Tried it last night, 1nf 5kv cap across the output of the "unused" inverter. The set still shut down.

Should I perhaps try a higher or lower value? If so, what value would I be safe using that wont cause damage to the inverter (I guess as this is a tandem unit causing damage to the unused side may affect the other)

To confirm the top tube is definitley faulty, I gently opened the panel and powered up the TV. Sure enough, the top tube didnt light.

Jim