Tv fried psu diode

[socrates75]

Ok so let me first show the picture of the damage to see if its even something i can fix and then onto the problems that led to this point. The tv model is DMTECH LQ37XTQ This is a pic of the PSU https/imgur.com/CIltQLw

Ok so this tv has been with me for years, first the built in dvd player stopped working but i was able to pull the guts from it and put the guts from an external dvd drive that matched the guts perfectly, workd like a charm, but then a few years later the tv started to not turn on unless i unplugged it and waited for 60 seconds with the power button pressed in, then plug it back in and it would come on after 8 to 10 seconds, this was about once to twice a month, then it started to make the high pitched scream and not turn on even after doing the 60 second thing but after a few times it would come on, well then it started happening every morning after having used the sleep timer the nght before, wouldnt come on, but then one day i got it back on and it smelled like burning wires but it worked great for weeks, came on everytime, but it always smelled real bad like burnng wires, so i checked it out, all the caps look ok, and no visual damage anywhere that i could see, i even have pics of the area that is burned before it was burned, but tonight it just wouldnt start, so i opend it up and found those burnd diodes, so im wondering if the dioeds are what was causing the problems cause now the tv wont even show power to the light anymore....so is it possible for me to clip these 4 diodes and put in 4 new ones? will it solve the problem or are the diodes just the beginning of the problem? Thanks in advance

 

[Grugbug]

I had a projection tv that lost the convergence ICs along with a few diodes. I replaced the ICs and some diodes and had a tv that worked for several more years until the same components failed again, I upgraded to a new set.

Diodes are cheap so you would only lose some change plus your time if the fix doesn't work.

 

[kanewolf]

I would say that there is too much current (short) somewhere that is causing the burning. This whole area is overheating. If you have a multi-meter, you can easily check the diodes. You should get continuity in one direction and if you flip the leads you won't. Many multi-meters have a diode check function.
I think this is a symptom and not a root cause.

 

[socrates75]

So could it be the caps on the PSU causing the problem? and would you happen to know what kind of diodes i would need to replace these ones?

 

[kanewolf]

I don't know you NEED to replace them. You have to desolder one end of the diode and test each one. There are numbers printed on the diode which will allow you to find a replacement.

 

[socrates75]

Ok i will see if i can get a multi tester in a few days, so lets say the diodes turn out still ok, then how do i find out what is causing it to not power on at all now, theres no light anymore

 

[kanewolf]

You really need a schematic to do any significant trouble shooting, beyond the board replacement level. You don't have the most basic of test equipment. I believe you could hurt yourself more than repair this. You are over your head, IMO.

 

[socrates75]

Ya i feel comfortable replacing diodes and caps but anything over that i agree i might hurt myself 😉 i have looked for replacement boards for the psu but only found 1 and its in the UK well im in canada,you would happen to know of anywhere that i can find a new PSU for this model of tv would you? the model number for the PSU is PS-3700, i have found other ones with the same model number but it says there for different models of the dmtech tv, would the still be ok to use in this model?
also im picking your reply as the best answer and thanks for the help

 

[socrates75]

http/www.ebay.ca/itm/302102811026?ul_noapp=true

What about that one?

 

[socrates75]

Ok i replaced the caps on the PSU and replaced the diode but it still wont come on, now it just makes the high pitched scream noise and sits there changing pitch in the sound, is the psu dead dead and should i replace it or does it sound like theres more damage down the line?

 

[kanewolf]

Did the diode test bad? What about the other 3? You are blindly trying to fix this without a schematic.

 

[socrates75]

I think im just going to replace the power supply, the fact that it burned the board and i replaced all the caps is enough for me, what are the chances though that i replace the PSU and it still doesn't turn on?

 

[kanewolf]

No idea. You don't have a root cause. Could be on the board, could be a short somewhere else.

 

[socrates75]

Ok thanks for all the help im thinking either replace the board or find a used tv online to replace the whole thing