How I diagnosed and fixed my Emerson LF391EM4F LED TV for $40.

The Story

How I diagnosed and fixed my Emerson LF391EM4F LED TV for $40. It died in October 2015 about 13 months after I'd purchased this refurbished (3-month warranty) unit. This seemingly occurred after a power outage (or two). Yes, it's plugged into a surge protector as was everything else attached to the TV - except for the coax cable from my cable company.

Symptomatic Description

The unit powers on with a steady red standby light. However, I could not turn the unit on using either the remote or mechanical buttons. The red light never flashes, remaining steady.

For a couple of days after the power surges, if I unplugged the unit for a minute or so - to reset it - and then plug it back in, it would work; both the remote and the mechanical buttons would turn the TV on and off - until the next day. This worked for 2 maybe 3 days, but then the unit stopped responding to either input. Based on forum posts, I even left it unplugged overnight, tried the 60sec mechanical on button hold (while plugging in - and continue holding after). No changes in symptoms.

So I hit the web and started reading how to fix LED TVs. It probably wasn't worth paying someone else to fix this bargain brand unit. With my background, I felt I should be able to fix it. This included several hours of research, reading forums, blogs and watching YouTube videos. None truly specific to my unit and particular situation.

Diagnosis

I still get a solid red standby light - even with the LED power and T-Con cables disconnected.

A visual inspection of the power board shows no capacitor bloating problems and everything else looks clean and solid everywhere. I do get power off the board but have not checked all diodes and such. However, the standby light supposedly suggests the power board is working fine.

I finally found a service manual listing the unit as made by Funai as both Emerson LF391EM4 and Magnavox 39ME313V/F7. That helped some on the searching as well as truly being able to service the unit - even if mine was a little later model LF391EM4F.

I first thought (hoped?) it was the IR/Buttons board based on reading posts on the web. Some other posts suggested it was that or the Main Board. But I found no definitive info on this particular model, nor for my specific situation. So I posted to DIYforums my Emerson LF391EM4F - Steady Red Light diagnostics and diagnosis - and was then told it was most likely the Main Board (thanks to my10cents).

I was disappointed to hear that because it was much more expensive, but I confirmed that diagnosis using the diagnostics flowchart (Video Signal Section, Flow Chart No. 1) in the service manual - the voltage does decrease on Pin(6) on the CN4052 connector on the Main Board when the Power button is depressed on the IR/Function CBA Unit which suggests it's the Main Board and NOT the Function CBA Unit (aka IR sensor board).

After searching for 2 days, I found one - for what I considered affordable - from ElectroParts, found via eBay ($40). It arrived fairly quickly, and I installed it. Voila! It was indeed the correct part that made things work again. I'll note ElectroParts offers 50% off your first order, and 5% off every other order (the codes are posted on their website).

Part Numbers and Other Information

Emerson LF391EM4F (refurbished)
S/N ME1******** (A3ATKUT) (label placed over the original 2EMH00264)
Similar Models: Emerson LF391EM4, Magnavox 39ME313V/F7
Manufacturer: Funai

Two Types (according to Service Manaual): A or B (but none of the listed models in the service manual match A3ATKUT) and there is (at least) a third type with S/N starting ME1. Finding the part numbers for this third type has been difficult at best.
A: S/N DS2
B: S/N DS1, DS3
X: S/N ME1

Motherboard: P/N: ME1: A3ATHMMA-004 (Board BA3ATHG0 201 3, A3ATK013)
Pics: A3ATHMMA-004 | A3ATHMMA-002 (supposedly either will work)
Locations: ElectroParts (found on eBay, best deal), PartsRunners (free ship, 6mo wrty, 21d return), TVPartsBay (6 mo wrty, 15-day return), I found other sites more expensive. ShopJimmy didn't have my needed part.

Function CBA Unit: P/N: ME1: A3ATHMSW-001 (Type A: A3ATCMSW-001 | B: A3AT0MSW-001)