Need Some Help

[multimeter]

Re: Need Some Help

the lines marked in red that ive done,is the standby voltage to the "on" signal,you can connect a 3 ohm resistor accross these 2 pins and see if your 12v/24v comes up,i dont think this is a main board issue though,beacause you swapped psu's,but the signal to power the psu up will come from the main board.

there are a bank of caps around the connectors,those are your output caps,heat those up as you did the others,and see what happens,if nothing will have to dig deeper.

this whole problem is screaming cap issue !

[burner6999]

Re: Need Some Help

Yeah when I switched the power supplys all is good and if I put this PSU in the other working tv it does the same thing. So it has to be the PSU. After doing some more trouble shouting of my own I decided to pull those 4 small caps and this is what I found(PIC). They are 50V 22uf caps. Now I have a question I dont have any of that size but I have some 50V 10uf of the same size. Could I use them? Just as a trial thing of course. For testing to see if I need anything else before I order the new ones.

[multimeter]

Re: Need Some Help

a little higher in capacitance would be ok,but not lower,normally if i get confused on a board,il recap it as a good bench mark to rule them out,if you do this replace the lot with panasonic fm/fc ,apart from the large filter cap ,you can leave that one.

[burner6999]

Re: Need Some Help

So you are saying I should just do them all?

[multimeter]

Re: Need Some Help

So you are saying I should just do them all?

if you dont have the equipment to test the output caps,or any of them,then yes i would say replace them all apart from the filter cap,they hardly fail,only on occasions,to pick and choose which caps to change you need a esr meter.

then you will know the new caps will not be the problem,most psu's have crap caps in anyway,so you will be doing yourself a favour ,and will have the tv a lot longer!

back to basics:

check psu main fuse

do you have a multimeter?,what range?,a picture of it?

check the bridge rectifier,pins 1-4. 1-2 should have reading one way when reversing the probes,pins 2-3 should have no reading either way,pins 3-4 should have reading one way when reversing the probes.

what voltage is on the main filter cap with power on?
resistance check each pin of the connectors voltage outputs with respect to ground point,readings should be very high resistance,if you get a few ohm,this means there is a short on that rail.(somthing around 30ohm) could indicate a fault condition.

check for cold joints on solder side,reflow where suspicious.

you said you had a spare psu,compare readings against the working one.

put the working psu in the tv,measure the actual voltages you get from the connectors

all this is a good base for us to be able to fix your tv,and is also a good learning curve

[burner6999]

Re: Need Some Help

I ordered all the capacitors and they should be here Monday. I will post back after I install them. Thanks for all the help guys.

[burner6999]

Re: Need Some Help

Ok so I ordered all the caps got them installed and there is no change. I checked some of the voltages with the working supply and the pins in red top right have nothing on the bad one but 430v on the good one. A resistor also burned out. It is marked in red. bottom left.

[selldoor]

Re: Need Some Help

Ok so I ordered all the caps got them installed and there is no change. I checked some of the voltages with the working supply and the pins in red top right have nothing on the bad one but 430v on the good one. A resistor also burned out. It is marked in red. bottom left.

Are you saying the resistor burnt out on the non working board when you tested it after fitting new caps?
First thing - get both boards togther and check again that you have put the caps in the correct way round.

Next - just above the top red box there is a component with 3 legs - the soldering on that looks a weird and also going left there are another two
sets of three. Can you list the part numbers of those 3 components.

[burner6999]

Re: Need Some Help

Checked all the caps. They are all good. Here is a pic of the mosfet. I couldnt find anything on digikey for it. Here is a link to the datasheet I found. The first 2 from right to left are the same. And both have the same voltage on the working supply and nothing on the other. Also now the filter cap is only reading 180vDC instead of 390.

[selldoor]

Re: Need Some Help

Hi - here is the datasheet for it - were all three the same.
It is a Dual High-Voltage Schottky Rectifier
What was the soldering like does it need re-done

[burner6999]

Re: Need Some Help

Soldering looks good. Only 2 are the same.

[selldoor]

Re: Need Some Help

Also now the filter cap is only reading 180vDC instead of 390.

Battery in meter ok and on VDC? - are you testing directly across the legs of the big cap?

Did you replace the burnt resistor?

[burner6999]

Re: Need Some Help

Not yet I need to order it. But I want to see what else I need first.

[burner6999]

Re: Need Some Help

Ok so I pulled the whole heat sink and checked them all with my multimeter on diode and the picture has the results. NC means no change. Also the way they are labeled is the only way I get anything. Also I am not sure which resistor to order. I know it says 220 on it so it is 22 ohm but I am not sure what size or watt to get.

[burner6999]

Re: Need Some Help

Anyone have any input?

[burner6999]

Re: Need Some Help

Bump

[burner6999]

Re: Need Some Help

Ok well I started doing some stuff on my own. I took the other heat sink off and did some testing and found a bad fet. Also after I took it off the heat sink there was a burn mark under it and on the other side of the board where the bur mark was I found this. and it was right in line with the resistor that burnt out. I ordered the resistor and a new filter cap just in case.

[burner6999]

Re: Need Some Help

Does anyone have any ideas? A friend of mine said he thinks it may be a power IC there is a long one on the board. Do you think that could be it?

[selldoor]

Re: Need Some Help

Ok so I pulled the whole heat sink and checked them all with my multimeter on diode and the picture has the results. NC means no change. Also the way they are labeled is the only way I get anything. Also I am not sure which resistor to order. I know it says 220 on it so it is 22 ohm but I am not sure what size or watt to get.

I dont know what your results mean can you put them in a table - should be 3 results for each

Mosfets

If you have a manual range multimeter, set it to 200 ohms (two hundred). This is for 3 pin ICs only. You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any reading is less than 30 ohms you might have shorted mosfet. Remove from circuit and repeat the tests to verify.


Also you keep asking what to test next but at some point you are just going to have to order what you know or think is dead and replace it. At that point you can test again. We normally suggest buying more than one of what you need just in case it blows again.

Just for future advise the heading you chose is terrible - everyone on here need help so you need to say what you need help with then anyone who knows anything about those key words will respond - some experienced members dont even bother reading "need some help" type threads

[vinceroger69]

Re: Need Some Help

as per your post 37 that looks like a regulator of some kind if it has a burn mark on the board it is probably shorted i would test/replace it.