Proscan 42LA45H PSU Problem

[Nr1Ctr]

Hello all!

I've got a Proscan 42LA45H LCD flatscreen that has PSU issues that I'm trying to fix. I looked at the other posts related to this TV and particular board but the problem I'm having seem different. The unit has standby power but will not turn on. This first thing I checked, thanks to you all and others on google, was the caps. I found one that was obviously bad and changed it out. The others looks fine, but I have no way to test them as all I have is a cheap DVM.

There is also a humming noise coming from the PSU board after I plug it in, and I'm not really sure if it was there before I changed the cap. I checked all the voltages coming off the board and they are as follows:

gnd - 0
gnd - 0
sw - 4.24v
sw5 - 4.96v
sw5 - 4.96v
12/5 - 0.12v
12/5 - 0.12v
gnd - 0
br? - 0
on - 0
gnd - 0
gnd - 0
m5v - 0.01v
m5v - 0.01v

I have attached pictures of the board with the new cap and a pic of what I took to be the bad (old) cap. If anything else is needed please let me know. I'm really just looking for ideas of where to go from here. I got this set for free, courtesy of someone who dropped it off at the dumpster by my place. Figured if I could change a couple caps, or something cheap anyways, it would make a nice Christmas present for the kids. If not, ill just haul it back out there. Thanks all, and I look forward to talking to you.

edit: Also, I assume that light at VD824 (bottom) is supposed to light up, but it doesn't.

[budm]

Re: Proscan 42LA45H PSU Problem

Can we see the pictures of the whole board, top and bottom side of the board, and also the pictures of the whole back side of the TV so we can see all the boards and how they are connected together?
Also need the pictures of the connectors so I can see all the pin labels.

http://www.shopjimmy.com/proscan-114...wer-supply.htm

[CapLeaker]

Re: Proscan 42LA45H PSU Problem

sounds like your mainboard isn't returning PSon to the power supply. So the power supply doesn't turn on.

[budm]

Re: Proscan 42LA45H PSU Problem

gnd - 0
gnd - 0
sw - 4.24v = PS-ON
sw5 - 4.96v = 5VSTBY
sw5 - 4.96v[/B] = 5VSTBY
12/5 - 0.12v = SWITCHED 12V
12/5 - 0.12v = SWITCHED 12V
gnd - 0
br? - 0 = DIM CTRL
on - 0 = BL-ON
gnd - 0
gnd - 0
m5v - 0.01v = SWITCHED 5V
m5v - 0.01v = SWITCHED 5V

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

More pictures as requested. It'll be a couple hours before I'm back on here. Taking an Assembly Language class (one among many) and I've got a test today. I'll try and check on my phone. Thanks again

Took me 30 minutes to upload the pics, lol. Hope you don't need many more.

[budm]

Re: Proscan 42LA45H PSU Problem

Thanks for the pictures, I may need more pictures of the bottom side if I cannot trace out the circuits, I'll let you know.

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

Alright then. Back in a bit. Test time..

[CapLeaker]

Re: Proscan 42LA45H PSU Problem

I guess I better go back to bed.

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

Back now. I like assembly. Only problem is that for every line you write in C++ you have to write 10 (or 100) in assembly. Will be here for a few hours now if anyone has some idea of where I should go from here.

[budm]

Re: Proscan 42LA45H PSU Problem

OK, I need 4 pictures (1 pictures of large red box, and then 3 sections of the bottom half of the board) total that are clear and without the glare because I cannot easily see the traces. Please do as close focused as you can.

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

Ok. Will get em first thing in the morning. I can email you the pic from my phone if you want. It's much higher quality and a lot easier to see the traces.

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

Here's the better pics. I took 4 instead of 3 going across from left to right. And a zoom in of the box you outlined. Hope you can get better visualization. My camera was having a hard time focusing but with more light it gave the glare again.

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

Are these good or do I need to get clearer ones?

[budm]

Re: Proscan 42LA45H PSU Problem

I am downloading them right now.

[CapLeaker]

Re: Proscan 42LA45H PSU Problem

gnd - 0
gnd - 0
sw - 4.24v = PS-ON
sw5 - 4.96v = 5VSTBY
sw5 - 4.96v[/B] = 5VSTBY
12/5 - 0.12v = SWITCHED 12V
12/5 - 0.12v = SWITCHED 12V
gnd - 0
br? - 0 = DIM CTRL
on - 0 = BL-ON
gnd - 0
gnd - 0
m5v - 0.01v = SWITCHED 5V
m5v - 0.01v = SWITCHED 5V

Was sick yesterday

[budm]

Re: Proscan 42LA45H PSU Problem

OK, please see the attached picture, we will need to get P/N of the M5V switch and the 12/5V SMPS IC, and Voltage at VCC2.
Check the DCV on all 3 pins of the M5V switcher.
PS-ON is present but it is not turning on the M5V switch and the 12/5 SMPS.

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

Ok. I will have to figure out how I can hook it up to power and still get access to the back of the board. Will let you know what I find. Thanks again!

[budm]

Re: Proscan 42LA45H PSU Problem

At least give us the P/N of those two devices so we can look up the spec sheet for them.

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

Here are pics of the two in question. Will get back to you about the voltage soon as I figure out how to get it without zapping myself.

[Nr1Ctr]

Re: Proscan 42LA45H PSU Problem

Does it just need the AC power hooked up or do I have to make sure all the ribbon cables are connected?