Emerson LC401EM2F no standby light or power

[Beef_Ramen]

So i found this tv on the side of the road, and have repaired everything i have identified to be nonfunctional. I'm looking for suggestions on what to try next, i have attached a video below which explains everything in more detail. If you have any suggestions or help whatsoever please post it, I have checked this forum and various other sites but still need some assistance.

https://www.youtube.com/watch?v=PyiBtmWuzQk

[budm]

Re: Emerson LC401EM2F no standby light or power

Please upload good clear straight shot pictures of the that power supply board top and bottom side, and the pictures of the whole backside of the TV so we can see all the boards, that will be a start.
BTW, are these the exact match of your boards? It also has repair kit for the power supply board.
http://www.shopjimmy.com/catalogsear...rson+LC401EM2F

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

Please upload good clear straight shot pictures of the that power supply board top and bottom side, and the pictures of the whole backside of the TV so we can see all the boards, that will be a start.
BTW, are these the exact match of your boards? It also has repair kit for the power supply board.
http://www.shopjimmy.com/catalogsear...rson+LC401EM2F

Thanks for the reply. Yes, the link you provided is the same as my board. Also here are some pictures, if you need a closer shot of anything in particular let me know.

http://imgur.com/a/itSgD

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

Please upload good clear straight shot pictures of the that power supply board top and bottom side, and the pictures of the whole backside of the TV so we can see all the boards, that will be a start.
BTW, are these the exact match of your boards? It also has repair kit for the power supply board.
http://www.shopjimmy.com/catalogsear...rson+LC401EM2F

We're those shots clear enough?

[budm]

Re: Emerson LC401EM2F no standby light or power

I did not have a chance to download the pictures and study them yet.

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

Unplug everything from the power supply. Plug it into the outlet and measure the voltage on the main filter capacitor in the primary. Use both of your leads on that capacitor while measuring. Then there are 2 sets of ribbon cables going from the power supply to the main board. With the power supply plugged in measure all the DC voltages on those pins and post them with the pin out name.

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

I did not have a chance to download the pictures and study them yet.

No problem and no rush, if the pictures aren't clear enough when you view them just let me know, thanks again

Unplug everything from the power supply. Plug it into the outlet and measure the voltage on the main filter capacitor in the primary. Use both of your leads on that capacitor while measuring. Then there are 2 sets of ribbon cables going from the power supply to the main board. With the power supply plugged in measure all the DC voltages on those pins and post them with the pin out name.

Thanks for the reply. Bare with me, I'm rather new to most of this with the exception of recapping a few boards.
How exactly do I perform the tasks? I just want to make sure I do this right and understand it before proceeding.

[CapLeaker]

Re: Emerson LC401EM2F no standby light or power

Easy. Each switching PSU has 2 sections (see that line going through the PSU?). A primary and a secondary. The primary has the potential on mains power. So be warned. Each DC V measurement on the primary is with the GND probe of your DMM to the big high voltage main filter capacitor, while probing around with the positive probe. Be careful, if the PFC booster is turned on, you get roughly 400V DC on that main filter cap.
The secondary is isolated from the primary. Your GND reference for your negative probe is either chassis GND or the GND pins on the 2 connectors, or any GND point at the secondary.
Reason for post 6: if you have 170V DC at the main filter cap, that is good. If not, well there is something else shot in the primary. If you have 170V at that main filter cap, proceed probing the pins on both connectors on the PSU. I am looking for the standby voltage.
Here is how it goes. STBY voltage is always there on the PSU. That is going to the main board. When you press the on button on the TV, the main board returns PSon and BLon. In other words, it tells the PSU to turn on all the voltage rails and the back lights. TV turns on.
Right now we don't know if:
A: the primary has power on the filter main filter cap, in order to power the STBY circuit
B: there is something wrong with the standby voltage circuit
C: you got a bad main board.

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

Easy. Each switching PSU has 2 sections (see that line going through the PSU?). A primary and a secondary. The primary has the potential on mains power. So be warned. Each DC V measurement on the primary is with the GND probe of your DMM to the big high voltage main filter capacitor, while probing around with the positive probe. Be careful, if the PFC booster is turned on, you get roughly 400V DC on that main filter cap.
The secondary is isolated from the primary. Your GND reference for your negative probe is either chassis GND or the GND pins on the 2 connectors, or any GND point at the secondary.
Reason for post 6: if you have 170V DC at the main filter cap, that is good. If not, well there is something else shot in the primary. If you have 170V at that main filter cap, proceed probing the pins on both connectors on the PSU. I am looking for the standby voltage.
Here is how it goes. STBY voltage is always there on the PSU. That is going to the main board. When you press the on button on the TV, the main board returns PSon and BLon. In other words, it tells the PSU to turn on all the voltage rails and the back lights. TV turns on.
Right now we don't know if:
A: the primary has power on the filter main filter cap, in order to power the STBY circuit
B: there is something wrong with the standby voltage circuit
C: you got a bad main board.

Ok I'm understanding it more now.
I thought I would mention this before I continue, when checking the dc voltage on the main filter capacitor, it's only reading out 1.90~V with both probes on each lead. That's already a problem right?

[dick_barton]

Re: Emerson LC401EM2F no standby light or power

Can you read the voltage using your meter probes connected to each pin. Red to "+ " and Black to "-" across capacitor C1612.

You also need to check all the diodes using your meter set to diode mode.

Also check the white ceramic fuse, number I cannot read.

If there is an ON/OFF switch on the set then check that too.

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

1. Can you read the voltage using your meter probes connected to each pin. Red to "+ " and Black to "-" across capacitor C1612.

2. You also need to check all the diode using your meter set to diode mode.

3. Also check the white ceramic fuse, number I cannot read.

4. If there is an ON/OFF switch on the set then check that too.

Thanks for the reply

1. It's reading 1.90~ volts
2. I've checked all the diodes and they seem to be ok, I replaced 2 of them mentioned in the video I posted, which seems to make my fuse stop blowing.
3. Fuse has been replaced as mentioned in the video, it's showing 0.015 voltage in ac mode.
4. There is a power button on the TV, but I doubt that's what you're talking about

[vinceroger69]

Re: Emerson LC401EM2F no standby light or power

basically a power button can fail with bad contacts can you test the switch?

Theres a possibility i guess that this tv took a lightening strike so maybe why the psu had blown so bad on the underside, also if the tv had any inputs ie cable etc going to the main board that maybe damaged too but lets test the psu first and go from there. on the psu where the connectors are going too the ribbon cables/connectors can you upload pictures af them as sometimes it also gives voltages printed on the board and pin layout etc.

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

basically a power button can fail with bad contacts can you test the switch?

Theres a possibility i guess that this tv took a lightening strike so maybe why the psu had blown so bad on the underside, also if the tv had any inputs ie cable etc going to the main board that maybe damaged too but lets test the psu first and go from there. on the psu where the connectors are going too the ribbon cables/connectors can you upload pictures af them as sometimes it also gives voltages printed on the board and pin layout etc.

How would I go about testing the switch?
Here are the pictures

[dick_barton]

Re: Emerson LC401EM2F no standby light or power

Can you check the continuity of the two transformers highlighted within the red boxes using your ohm meter and then measure what ac voltage you have across the points indicated by the arrows.

[dick_barton]

Re: Emerson LC401EM2F no standby light or power

Just place your ohmmeter across the ON/OFF switch and it should be 0 ohms when the switch is in the ON position and OL when in the OFF position.

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

Can you check the continuity of the two transformers highlighted within the red boxes using your ohm meter and then measure what ac voltage you have across the points indicated by the arrows.

All points circled have continuity, the 2 points tested for voltage read 119.0~ volts

[dick_barton]

Re: Emerson LC401EM2F no standby light or power

Well that's something positive. Sothe PSU does has mains input voltage. So now to find the capacitor holding the rectified ac. Will look at your photo's to find it.

[dick_barton]

Re: Emerson LC401EM2F no standby light or power

In the yellow box shown, can you lift one end of the diode and test it and then measure the coil resistance of the relay.

[Beef_Ramen]

Re: Emerson LC401EM2F no standby light or power

In the yellow box shown, can you lift one end of the diode and test it and then measure the coil resistance of the relay.

Lift as in De solder one lead from the diode? If so does it matter which lead?

[dick_barton]

Re: Emerson LC401EM2F no standby light or power

Ignore that test for now.
You said you had 119V ac from the earlier measurement. There are 4 diodes that rectify the AC and apply it as DC to the capacitor C1612.
Measure once again across C1612, one probe on either pin with meter set to => 600V DC.