Replacing bad caps in MLT386X PSU

[atr730]

hi, I found this cool forum while searching the web for information. Many thanks to everyone ahead of time for any help.

Problem: I recently received a half-broken tunerless HDTV (works when it wants) with the MLT386X power supply. The first thing I did was open-up the psu from advice at avsforum.com and noticed alot of caps have leaked and few with bumps. The HDTV shows major distortions and "snow flakes" when it works. But when it doesn't, I can turn it on but see nothing except white snow flake screen.

About Me: I, myself have computing experience but not much electrical. This is my very first attempt to fix the psu. I have very litter soldering experience.

So far what I did, purchased

2x CapXon C634 - 1000uF, 10v > 2x NTE VHT1000M16 - 1000uF 16v
2x CapXon C632 - 470uF, 16v > 2x NTE VHT470M16 - 470uF 16v
1x CapXon C618 - 470uF, 25v > 1x NTE VHT470M25 - 470uF 25v
2x Decon 470uF 35v (unsure if these are electrolytic caps and frys has no stock)

I hope that I can fixed it and used it as a monitor for my desktop. (Flight Simulator)

My hdtv model is: Viore LCT37V66HM (uses LG/Philips Display)

1) Picture of the MLT386X (heat-sink removed and exposing caps)

2) Description of each leaking caps.

3) Found some replacement parts at local fry's electronics. (I have a acct at digikey.com but fry's electronics was a 20 minutes drive.)

[selldoor]

Re: Replacing bad caps in MLT386X PSU

hi - welcome to the forum
Can you post well focused pics looking straight down on your board - both sides.
Please do not post in line - use manage attachments which is in Go Advanced which is below quick reply jpg files no bigger than 2mb 2000x2000.
They should look like this https://www.badcaps.net/forum/attachm...1&d=1290283049 so we can see board numbers and look for faults.

If you see this soon you can edit your inline pics out and replace.

You do not actually say what is wrong - a blow by blow account from switching on would help - lights sounds etc.

service manual :http://www.servicetron.com/uploads/2...sa01-10-07.zip

[selldoor]

Re: Replacing bad caps in MLT386X PSU

Not sure about NTE caps - shouldnt think they will be much good- data sheet doesnt even mention ESR - should be ok to get working but may not last long.
The Decon ones are electrolytic caps members here would normally recommend Panasonic FC FM series or similar Rubycon or Nichicon.

[atr730]

Re: Replacing bad caps in MLT386X PSU

I have re-upload the old images, removed direct links.

I will be going to a electronics store to buy proper and reliable caps (pana, nichicon...)


Ummmmm....
NTE capacitors are designed for both the most demanding applications and those not requiring tough characteristics. And most are available in axial or radial lead versions.
http://www.nteinc.com/capacitors.php?a=2

[tom66]

Re: Replacing bad caps in MLT386X PSU

I wouldn't trust the manufacturer.

-Most- CapXon are rated for demanding applications yet they still don't last.

You need low-ESR caps which cost a couple of pennies more. Digi-Key stocks them. Low-ESR caps are sometimes a requirement, not just a long life option.

[selldoor]

Re: Replacing bad caps in MLT386X PSU

Pictures are better but you need to give the board a brush down to get the dust off.
I would give consideration to replacing all the caps on this board except the BIG one (assuming that doesnt look bulged or leaky) with low ESR ones. Picture of the board underside.
Sorry you did say what was wrong I missed the snow bit unless you edited it in.
Did you try it with other inputs - pc scart

[atr730]

Re: Replacing bad caps in MLT386X PSU for HDTV

Can anyone answer these two noob questions.

1) What is the rule of thumb or recommendation when using higher voltage caps with the ones on this PSU?

2) I am researching everything at digikey.com before heading to local electronics store. They don't list much info regarding low esr capacitors.

cheers

All inputs are the same. Works when it does and when "it does" after awhile screen distorts. The funny thing is I noticed the ground wire was completely off of the grounding. I dont know if I pulled it hard or it wasnt on (I re-crimp it) I also see on one wire of the inlet unit is a burn just very slightly.

[tom66]

Re: Replacing bad caps in MLT386X PSU for HDTV

Can anyone answer these two noob questions.

1) What is the rule of thumb or recommendation when using higher voltage caps with the ones on this PSU?

Higher voltage is okay (it's only a maximum rating), but they will be physically larger, so might be difficult to fit on the board.

2) I am researching everything at digikey.com before heading to local electronics store. They don't list much info regarding low esr capacitors.

Very few electronics stores sell good quality capacitors. Shipping from digikey is something like $3. Use Panasonic FC, FM or FR, or Rubycon ZLJ/H, or Nichicon HN/HM, or United Chemicon KY/KZE.

[atr730]

Re: Replacing bad caps in MLT386X PSU

thanks, mate I will post back with my finds.

[tibimakai]

Re: Replacing bad caps in MLT386X PSU

http://www.findonefindall.com/toyota..._LG_LCD_tv.htm

[atr730]

Re: Replacing bad caps in MLT386X PSU

I managed to re-solder the caps. I think is the same... I tried HDMI and VGA only the vga is working (I am using for Flight Simulator) on my desktop. It also still show some distortion like interference. I don't know if is due to the cheap surge protector I have or what... But thanks everyone for tips and support.

[ddk]

Re: Replacing bad caps in MLT386X PSU

Hi all, I'm happy find this forum, and I Hope my LCD will coming back,
please help to find out my missing caps size & volt components
mark with yellow arrow. I forget where I put these caps when I want to buy this replacement caps. many thanks and sorry for bad my english

[softtech]

Re: Replacing bad caps in MLT386X PSU

please help me with the positions of the capacitors in the image below I removed them from my Mlt386x power supply but misplaced the mapping note

[softtech]

Re: Replacing bad caps in MLT386X PSU

Please can anyone assist me in determining the location of the following capacitors which i removed from my MLT396x power supply but carelessly misplaced the mapping note I took while i was searching for replacement.

[Hamie]

Re: Replacing bad caps in MLT386X PSU

Cant seem to locate a schematic for this psb so unless someone owns the supply you're outa luck.

Why not message someone on ebay who owns the supply and ask them?