Rca 46la45rq won't turn on

[Blndreaper]

I recently came across a 46" Rca 46la45rq. The unit would not turn on, no red light, no blue light and no power on the power supply. In checking the voltages coming from power supply I figured that had to be the problem, so I ordered a replacement and installed it. Now I get 5v and 3v in several different locations on the power supply, but nothing at all on the 12v or the 24v outputs. After I replaced the power supply the status light began working (turns from red to blue when pressed) but still no image and no 12 or 24v. I'm beyond outta my league here and don't know much about any of this, but I've been reading a lot and just can't seem to pin the problem. Could it be that I got a second bad power supply?..

[CapLeaker]

Re: Rca 46la45rq won't turn on

I guess there needs to be more testing done. Maybe load up some high resolution, straight shot pictures from the PSU and the Main Board. Then we can start some troubleshooting on that thing, before you just throw money at it.

[Blndreaper]

Re: Rca 46la45rq won't turn on

Ok, I'm at work atm, but I'll get some good pictures when I get home in just a couple hours. I feel like I made some progress by at least getting the status light on and functional, but I could still be way off. Any and all help is appreciated! As of right now I'm only $17 into this tv, but I still don't want to turn it into a money pit..

[CapLeaker]

Re: Rca 46la45rq won't turn on

Make sure the pics are good, so we can see everything. Also make sure we can see the pin outs on the PSU, we are going to need them.

[Blndreaper]

Re: Rca 46la45rq won't turn on

The power supply on the pink bubble wrap is the old one.

[CapLeaker]

Re: Rca 46la45rq won't turn on

How the TV works. STBY voltage is always there. That goes to the main board. When you press that 'On' button, the main board sends PSon and BLon back to the PSU. The PSU should turn fully on, the back lights turn on and the TV boots up and runs.

Unfortunately I can't read the full pin out on the connector I needed.

What you need to figure out is:
Is the main board sending PSon and BLon?
If it does send PSon and BLon, what is the DC Voltage on the high voltage main filter capacitor on the PSU in the primary section?

You can test the PSU by:
Unhook the main board from the PSU, just leaving the back lights connected. Find two 1k Ohm resistors and jump STBY voltage to PSon pin. Take the second 1K resistor and jump STBY voltage to the BLon pin.
Once you plug the PSU in, it should turn on all voltage rails and the back lights should be on.
Be careful at the primary side of the PSU. You are connected to mains voltage, heat sinks could be live, the main filter cap could have close to 400V DC on it, etc.

On the old PSU: If it doesn't have 5V STBY, it can't turn on. So you would have to troubleshoot the STBY section on that.

[Blndreaper]

Re: Rca 46la45rq won't turn on

I'm sorry, I tried to do good on the pictures, but I obviously missed the important stuff I'll take more if I need to. But I'm assuming that your looking for what pins the ps and bl on are? I just downloaded a service manual to find these pins and I found the PSon but no BLon. Even the ps on isn't marked as such on the board, so how do I go about locating the bl on pin? I tried answering that question for my self but I really don't know how to go about it now that my searches came up empty handed.
If I can find any local I'll grab some resistors on my way home tonight and try what you said!


Here's the link for the manual I downloaded: service manual

[dskall]

Re: Rca 46la45rq won't turn on

Will need pictures of power supply connectors to identify pins. When you turn tv on you should get voltage on pson. If there is a fault it will go back to stand by. When you first turn it on before it goes to standby you should briefly get proper voltages on on your outputs 12v 24v etc. If you get all proper voltages chances are power supply is not the problem.

[CapLeaker]

Re: Rca 46la45rq won't turn on

Actually we need a picture of the main board and a picture of the back side of the TV with all boards connected so we can see how it is hooked up.
There are a few PSUs under that model TV. Maybe the 24V are on as soon as PSon is applied. You may lso have a look at the inverter for the BLon. It all depends on how that thing is designed.

[Blndreaper]

Re: Rca 46la45rq won't turn on

Ok, I'll get those better pics this afternoon and try that with the resistors! One thing that just crossed my mind is that the port that the inverter board connects to is flipped around backwards on the new power supply. Would that be an issue? It's the exact model number as the old power supply and in every other way is identical you just have to spin that one cable 180° compared to the old board.. I found a video on YouTube when I got this TV about diagnosing issues similar to this and he stated that the 12v and 24v are always hot even if the tv is off. I don't know how accurate that is, but just trying to be thorough in telling what I know about the problem.. I really appreciate the help!! I'll post back before the nights over with some pics.

[CapLeaker]

Re: Rca 46la45rq won't turn on

Depends on which way you spin that cable. The polarity on that connector must be correct, other than that the PSU will see a short and shut down.

[Blndreaper]

Re: Rca 46la45rq won't turn on

Went to my local radio shack and they are closing the store in 5 days so they had no resistors anywhere near what I was looking for. I'll have to go to the next closest radio shack.. I'll update when I'm able to get them

[Blndreaper]

Re: Rca 46la45rq won't turn on

Double post

[Blndreaper]

Re: Rca 46la45rq won't turn on

Jumped bl-on and ps-on* with 1k resistor to 5vsb (double checked for 5v with multimeter)with only back light plugged in like you said and unit showed no signs of power. Not even a red or blue status light.

Connected everything back like normal and have
-4.03v when turned on at pson on psu
-1.74v at blon when turned on on inverter board (same voltage coming from main board)
Jumped 5vsb with 1k resistor directly to blon with every other wire connected.(pulled bl-on wire from connector) still not even a backlight

Tried to cover all bases.. still no luck and I don't know what any of this means..

[Blndreaper]

Re: Rca 46la45rq won't turn on

OK scratch that. The jumping pson to 5vsb turns on all voltage. 12 and 24v. Jumping the blon seems to have no effect on turning on backlight.. everything else I said is still true

[budm]

Re: Rca 46la45rq won't turn on

So are you saying that if all the connectors are back in place you do have 4VDC (post #14) at PS-ON (STB) pin when the TV is turned on but still no 12vdc/24VDC, but you can forc on the 12v/24vdc using resistor? Please clarify, something is not adding up.
BTW, STB pin is the same as PS-ON.
MEGMEET MLT198TX.

Megmeet MLT198TX (RE46MK2651) Power Supply Unit
http://www.shopjimmy.com/megmeet-mlt...er-supply.htm#
Pictures provided by shopjimmy.

[CapLeaker]

Re: Rca 46la45rq won't turn on

So you had success to fully turn on the PSU, but the back lights wont turn on. You have main board sending BLon.
When you have the PSU forced on with PSon and BLon, the 12V and 24V are up and running?
As budm already mentioned, right now something isn't adding up.

[Blndreaper]

Re: Rca 46la45rq won't turn on

Correct. The only way I see 12 or 24 v is to jump with resistor from ps-on(stb) to 5vsb. And with all cables connected I do get 4.03v at the ps-on, but no 12 or 24v

[Blndreaper]

Re: Rca 46la45rq won't turn on

And yes with everything connected the main board send bl-on but only 1.74v.

[budm]

Re: Rca 46la45rq won't turn on

Correct. The only way I see 12 or 24 v is to jump with resistor from ps-on(stb) to 5vsb. And with all cables connected I do get 4.03v at the ps-on, but no 12 or 24v

That is not making any sense to me right now, you can force on STB pin high using resistor and you get 12V/24v, but if the same pin is getting 4.03V from the main board when the power supply is connected back to the main board but you do not get 12V/24V.
Try it again with everything connected except the cable from power supply to the inverter board and see if 12V/24 will be present or not.

BTW, is this your LCD panel model? T460HW03 V.F