Emerson LC401EM2F no standby light or power

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

Check what voltage you get on pin 4 (VCC) of that IC.

I know this sounds bad but where do I put the negative probe when checking pin 4?

So just to be sure, you do not have the DCV at ALL+4.3V jumper for sure?

Correct I do not have voltage when testing the ALL +4.3V black ribbon connector piece.

[budm]

Re: Emerson LC401EM2F no standby light or power

"I know this sounds bad but where do I put the negative probe when checking pin 4?"
The black probe goes to the negative leg of the main filter cap. When you working in the dc primary side of the circuit, the negative leg of the main filter cap is the GND REF. for the meter, in the cold side of the circuit, the chassis is the GND REF. for the meter.

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

I know this sounds bad but where do I put the negative probe when checking pin 4?

What bud m said above or my post #8.

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

"I know this sounds bad but where do I put the negative probe when checking pin 4?"
The black probe goes to the negative leg of the main filter cap. When you working in the dc primary side of the circuit, the negative leg of the main filter cap is the GND REF. for the meter, in the cold side of the circuit, the chassis is the GND REF. for the meter.

Thanks for that, still learning even basic things like this.
Anyway with the negative black probe on the negative lead of the main capacitor, and positive probe on pin 4 of that IC, it's reading out -55DCV

[budm]

Re: Emerson LC401EM2F no standby light or power

Are you sure you have the meter set correctly and using the right cap, the cap that you measured 160VDC (the filter cap for the standby power supply)?

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

Are you sure you have the meter set correctly and using the right cap, the cap that you measured 160VDC (the filter cap for the standby power supply)?

You were right, sorry about that, ok so black probe on C1201 negative lead and red probe on pin 4, I'm getting 63DCV~

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

What bud m said above or my post #8.

Are you sure you have the meter set correctly and using the right cap, the cap that you measured 160VDC (the filter cap for the standby power supply)?

Anything else I should try?

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

post DC V measurements from all the pins from that IC. You may have to replace C1204. What is written on C1204? Check D1206 and D1207 and replace that IC. Kinda high voltage having 63V on a IC that should have max 45V.

[bman4]

Re: Emerson LC401EM2F no standby light or power

I have this psu from a emmerson im working on. It has a blown main fuse and seeing some dead shorts on sot-220s an diodes. Removed the doubble diode sot220 near the inverter d1721 tested good. Im getting 0.0 ohm then starts charging a cap on d1721. I have yet to power on the psu and test.volts because fuse . the mip ic1201 is not shorted.testing sot220 q1062 & q1601 right now but lcr enter self.test mode. Just tested q1602 to be bad but q1601 good!
Q1601 is a fairchild k8a50d 500v 8a n channel feild effect transistor.

Back to testing ,
Bman4

[bman4]

Re: Emerson LC401EM2F no standby light or power

Im measuring Schottky Barrier Rectifier diode 662 by cold section yelllow trans former With vf of 0.200 and others under . d656 reads 0.387. I think Schottky Barrier Rectifier diode are not supposed to be below 0.3v

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

a schottky diode should have a low voltage drop. So 0.2V drop is normal on these. If you in doubt, lift a leg, measure the voltage drop and compare it to the spec sheet. You do not want to see a total short on a diode, that's bad. Since there is a FET blown, I am pretty sure that there is more wrong with this PSU. Usually there are some shorted diodes, bad resistors that are either open or gone high in value, blown zener diodes etc.
You can have a look here in what you might be in of: https://www.badcaps.net/forum/showth...hlight=emerson

[bman4]

Re: Emerson LC401EM2F no standby light or power

they all tested 0.2+ but one small d670 reads 170.i was told there was a.voltage spike and the mains voltages are 125 .im hopeing it just took the one out and not the ic . i have one rjk6026 that is 600v but feel like its wrong to use 2 difrent parts . would it be a good idea to use orginals or the. Rjk6026 . i have 2pg011 but reads one less diode on my lcr. I fixed a 50u50 with just one part on ss and hope its that easy again.

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

no, you don't need to put in the original part. You can sub it, if you want, as long as the specs are close. THe 2pg011 is a IGBT, so forget about that. The RJK6026 has a better voltage rating, but the current rating is only half of the original and RDSon is way too high. Look for something like a 10N50 or a 12N60 TO-220-3 full pack and jam that in there. Tons of manufacturers make that FET. I think the origninal was a TK10A50D.

[bman4]

Re: Emerson LC401EM2F no standby light or power

you saved me alot of time looking for a better sub. I will report back when i test the improvisions with the fairchild 12n60. Finally just getting to know diffrent packages.i quickly thought 2pg011 because its 600v.just starting to think more clearly after being sick.

Thank you,
Bman4

[bman4]

Re: Emerson LC401EM2F no standby light or power

I installed the parts and i get a stand by light that flashed till relay shut down gotta test voltage but its getting stby tested 168.at tye filter caps . l tested ony 5v at pin 4 on bottom if thats the direction it counts. on ic1201 top 3rd pin reads 133.9 second pin reads - 315. First reads -125. When i was testing for groud chassis to filter cap gound i was getting a pulsating 0v. Fuseable resistors test fine. Maybee that ic. I get voltages allover to bcklight inverter. Hard to test main volages because they are covered by by the cable and no easily acessable test points. Gonna a get back to it tommrow.

[budm]

Re: Emerson LC401EM2F no standby light or power

When you make Voltage measurement in the hot side circuit, you need to use the negative leg of the hot side main filter cap as the GND ref. for your meter, not chassis GND. that is why your readings are invalid right now.

[bman4]

Re: Emerson LC401EM2F no standby light or power

Apologize about the bad grammar in the last post. It was long night and posted that b4 i went to sleep!
I did , wanted to see if Main filter cap was to chassis ground because it was hard to keep position.
I gor a flickering 0000 from main cap ground to chassis when i forgot to switch to continuity.
Ill have to look up data sheet and find out if pic ic 1201 pins are counted to the right on the bottom 4 pins

Filter cap: 168v

Ic1201
Top pin 1 : minus 125
Top pin 2 : minus 315
Top pin 3 : 133.9v

Bottom pin 4 : 5v

Baclight inverter shoots up to 125 going up and down.



Top 1:Tuner 35 volt top pin rises.
Pin 2 : The 12v for main is stable .
Pin 6:P on is 3.3 when it list 3.5.
Pin 8: 6.5 for tv is at 7.20 rising .
Pin10:p-on 3.5 for reg is stable at 3.7
Pin 12: P-on 5.0v is stable at 5.2
Pin14:24v amp rises

I know optocouplers stabilize voltage and must be damaged.there is 5 on this board. To test hot side they need to be powered on .
I think infound 2 bad optos .

Top one in righ conner facing rear of tv by backlight. the one in the bottom left below mini yellow transformer engaged protection relay when testing.

[bman4]

Re: Emerson LC401EM2F no standby light or power

Ic1201 i belive is functions but there is 2 bad optos . i got some stashed somewhere and gotta got find them.
Bottom pin 1:minus 45.1
Bp 2:56.3v
Bp 3:minus 56.4
Bottom pin 4 : 5v

[bman4]

Re: Emerson LC401EM2F no standby light or power

Replaced the optocouplers and get reading . the bottom right one under mini transformer engages protectipn shut down relay on hot side. This bottom right corelates with ic 1201.

[bman4]

Re: Emerson LC401EM2F no standby light or power

Might of been hard to under stand what i was explaining becausel i left out detail.
The optos i replaced where not getting a beep on continunity like the others when power was engaged.
The bottom right opto coupler engages protection relay when testing continuity on hot side unlike the others .. i belive it.corelates with ic 1201.i got 5.02 mega ohom reading on hot side of bottom right opto