Emerson LC401EM2F no standby light or power

[bman4]

Re: Emerson LC401EM2F no standby light or power

Backnlught circut only.gets 12v instead of 24v
Main votages are good and stable. No shorts on blacklight.

[bman4]

Re: Emerson LC401EM2F no standby light or power

Replace the optos with random ones without looking at data sheets . the 817c opto is from a 12v power supply and maybe this is why it only gets 12v now .
The 817c failed in place of the tlp781. Im just gonna have to order some proper ones.

[bman4]

Re: Emerson LC401EM2F no standby light or power

I got the new optos in today. The 3 others are getting a beep on cold side now . the top one of the two top left ones is not getting a beep.When i first replaced them with random ones the tv stby came one solid red. since the new optos its flashing as soon as i turn on the tv still .i let it sit in srby and now the protect relay is staying on. the back light is getting 14 v out of 24. On the two 12n60 the one that did not fail is shorted on 2 back pins on the board Witch leads to the ic .possibly the ic is bad. The output to the one that failed is not shorted but is to the second. Gonna order some ic's now. I isolated everything back to the ic so its the culprit now. I dont know if i.did something to cause this or it was already like this .

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

If there is a short to the gate of a Mosfet, then you have to check that gate drive circuit too. And don't change things with "random" parts from the junk bin. At least pull the datasheet and see if it is similar to the old stuff you took out.
Fix what you know isn't right with the correct parts. Then make yourself a "series light bulb trick" seen here: https://www.badcaps.net/forum/showthread.php?t=32748, plug the PSU into that and then fire it up. Other wise you may need a lot of more parts. Good Luck!

[bman4]

Re: Emerson LC401EM2F no standby light or power

the new12n60c mosfet 2 is not shorted but the ic on the back of board. It's odd that this pin failed on the ic when the one that is for the orginal shorted mosfet 1 didnt. Maybee the opto corelates with the mosfet 2 and that is why im getting half volts . the high voltage cap was getting proper vloltage.Here of some pics of the power supply with the parts circled. thought i checked all directions on the mosfets for shorts,I guess ill chalk it up to a rookie move.

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

so how much voltage did you get on the main filter capacitor?
These Emerson PSU's aren't that easy to fix. They blow not one component, but more like a dozen. There could be still blown zeners, open or gone high in value resistors too.

[bman4]

Re: Emerson LC401EM2F no standby light or power

168v and its a 400v cap so im guessing only half of it was working like i thought.I was only getting 168v while pressing power. Someone mentioned 168v is good so i dont know . i tested all diodes to be good . tested the through hole resistors that have mutiples to compare for the circut of the ic . The smd resistors that correlate with the ic where not open or shorted. the smd resistors are hard for my eyes to read them but realized i could get a clear picture. 223 = 22.16. 69c =50.2, 000=0.2, 124=120.1, 562= 5.55, 473=46.2, 222= 2.15, 510=32.45, 438=2.744, some seem like they match numbers within 10% but learned that the number don't allways match. R1605 and lifted one match and read 5.0. R1436=17.22 r1424=100.3. Im shure if i repalce this ic it will work. I think This psu looks minimal in parts to compared to plasmas. My first voltage post was wrong, had my meter on wrong. Thank you for your feed back have a great day!

[nomoresonys]

Re: Emerson LC401EM2F no standby light or power

168 is good in standby, should go up to around 400 when hit power on, be careful 400 volts is a shit-ton of volts.

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

so the pfc isn't working. No PFC = No 24V.

[bman4]

Re: Emerson LC401EM2F no standby light or power

Got the ics in and it and q1602 failed no short on ic or 1601. Tried it a second time with new ic and new q1601, q1602 .Q1602 shorted and the ic didnt again. I tested the pins on pcb before i installed them and there was no shorts both matched ohm reading. There was stby light.

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

read my post #64 again.

[bman4]

Re: Emerson LC401EM2F no standby light or power

do i put the lamp in series on the mains input on hot or neutral. i forgot to resolder a throght hole resistor r1606. I resoldered this resistor replace q1602 & ic and now it dose not blow the fuse or arc . Wow to think one through hole.ristor could.cause.that much chaos! stby light is blinking with the back light and i get a pic now. it cuts out after stby blink and repeats when power button is pressed. Tested all optos and they are all getting signal.zener diode d1605 is shorted but i think i lifted it before andnit tested good.

[bman4]

Re: Emerson LC401EM2F no standby light or power

That zener diode is shorted but what value do i replace it with. I see some zeners read like a schottky diode. I see a 2 horizontal then a vertical 2/ symbol in pic? it almost impossible to read.

[bman4]

Re: Emerson LC401EM2F no standby light or power

12n60 gate voltage is 2.7v. The Size of zener is small. Im guesiing 2.7v 1/2 w zener diode.

[bman4]

Re: Emerson LC401EM2F no standby light or power

The zener on the other transistor reads 0.620

[bman4]

Re: Emerson LC401EM2F no standby light or power

I threw in a zener diode that read 0.600 from a 12v power supply lwith what i just discoverd has a 2n60c.
Its up and running. Gonna to test for 24h

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

sweet