Samsung lt22a300

[sordids999]

Totally dead can't even measure voltages fluctuating all over the place

Any ideas

[tom66]

Re: Samsung lt22a300

Check for shorted diodes. I have one of these here, but no LED power cable or LVDS cable... good power board, screen and main board I believe.

[sordids999]

Re: Samsung lt22a300

Found one shorted number SR315A SHS OFI

[tom66]

Re: Samsung lt22a300

I would try replacing that then. If you ever get a smashed one of these let me know if you have the ribbons/cables left over.

[sordids999]

Re: Samsung lt22a300

Looking as we speak

[tom66]

Re: Samsung lt22a300

Actually just dug my power board out... same diode is bad.. hmm!
I guess it's a common failure. Never checked the board properly, got the TV for about £10 off a friend of a friend whose "tech" had looked at it.

[sordids999]

Re: Samsung lt22a300

what diode is it m8 looked on cpc but....

[tom66]

Re: Samsung lt22a300

3A 150V schottky,
https://cdn.badcaps-static.com/pdfs/...ec4595154b.pdf

CPC don't stock it (or a suitable replacement), closest is UF5402 but it will run hotter. Hard part to sub for. Might have to borrow a diode from another board.

[sordids999]

Re: Samsung lt22a300

hmmm got loads of boards but its finding the right one

[tom66]

Re: Samsung lt22a300

Alternative, it's a bit of a bodge, but you could solder two readily found 100V diodes together, e.g.
http://cpc.farnell.com/vishay-genera...20This%20Range

Keep leads long for best heatsinking.

[sordids999]

Re: Samsung lt22a300

ok ill try it cheers

[sordids999]

Re: Samsung lt22a300

all done and working again just need to monitor now

[billy1]

Re: Samsung lt22a300

Hi,
seems I have the same problem with my lt22a300 samsung.
I couldnt find a SR315A and tried you suggestion, but instead I used a IN5408 diode. Although the TV switched ON again, the diode didn't last long. I think the trick is the switch timing of the schottky, that is much faster than teh normal diode. I have to find a SR315 schottky to repeat the test. I'm pretty sure the SR315 is the problem.

[sordids999]

Re: Samsung lt22a300

unless im wrong here but the IN5408 is 3A 1000V but you need a 3A 100V diode

this may work

http://www.ebay.co.uk/sch/i.html?_fr...%2F54&_sacat=0

[billy1]

Re: Samsung lt22a300

Thank for the adequate response.
Today I gave it a really Q&D try... . I happened to have a STPS30150CW dual schottky (TO-247). (I know 15Amps per diode is really overdone). For the test I only used one diode and had to do some changes on the PCB, but this solved the problem! IMHO it really needs to be a schottky in this SMPS, as is has to have a high switching capability. Still need to order the SR315.

[billy1]

Re: Samsung lt22a300

My solution still works. I think I leave it that way.

[zwarder]

Re: Samsung lt22a300

CM855 1200uF 10V can cause no picture flashing standby led

[spiritfive]

Re: Samsung lt22a300

CM855 1200uF 10V can cause no picture flashing standby led

I confirm, I've just replaced it with a 1500uF 16V capacitor (JB JRG) and tv went back to normal (used to have no power to the screen at all + standby led working normally)