Ilo lct32ha36 dead

[Beowulf]

Hi,

This tv looks dead, meaning there's no LED on.

Looking inside none of the output voltages are present.

Both fuses are OK on the PSU.

I get 179v on both filter caps.

On 0565r IC this is what I get:

Pin
1-179V
2-GND
3-VARIES CONTINUOUSLY FROM 9 TO 14V
4-VARIES CONTINUOUSLY FROM 0 TO 3V
5-NC
6-VARIES CONTINUOUSLY FROM 0 TO 1.7V

Attached is the datasheet for the 0565r IC.

I'd appreciate any pointer on what to check next.

Regards,

[LDSisHere]

Re: Ilo lct32ha36 dead

I would advise you to pull the silver cover off of the main board(s) and have a look at the electrolytics there. I had one of these and the main board was covered in bad caps. One had even lost the outer sleeve.

[cashkennedy]

Re: Ilo lct32ha36 dead

I assume from your original post that you have used a resistor to start the power supply / and checked the voltages at the connectors on the edge of the PSU?

If that's correct then your on the right track checking the power supply as the power supply should be able to start on its own if you force it to regardless of the main board.

[budm]

Re: Ilo lct32ha36 dead

It sounds like that standby power supply is trying to start, try heating up those small caps by the IC with hair dryer for 2-3 minutes to see if you can get out put voltage at the filter caps on the secondary side of the transformer.

[Beowulf]

Re: Ilo lct32ha36 dead

I would advise you to pull the silver cover off of the main board(s) and have a look at the electrolytics there. I had one of these and the main board was covered in bad caps. One had even lost the outer sleeve.

Hey thanks for the pointers, I'll check it out just in case.

I assume from your original post that you have used a resistor to start the power supply / and checked the voltages at the connectors on the edge of the PSU?

If that's correct then your on the right track checking the power supply as the power supply should be able to start on its own if you force it to regardless of the main board.

Uh! I think this one is an always-on, also I still should be able to get standby voltages. Thanks for the input.

It sounds like that standby power supply is trying to start, try heating up those small caps by the IC with hair dryer for 2-3 minutes to see if you can get out put voltage at the filter caps on the secondary side of the transformer.

Alright I put some little heat on those caps and something weird happened, one smd resistor on the bottom side of the board blew up big time And no, none of the fuses got blown.

Hell I bought a board for $54 from shop jimmy. I'm not giving up on the repair though. I'll use the good board to help me fix this one and have two. Use one and post the other one for sell on ebay. Give me a few days to get back with an update.

Thx

[budm]

Re: Ilo lct32ha36 dead

Hmm, that SMD resistor that blew up seems to be connected in parallel with the other 2 large grey through hole resistors. Those resistors seems to be connected in parallel with the two large filter caps (450Vdc caps). Can you verify that?

[Beowulf]

Re: Ilo lct32ha36 dead

Hmm, that SMD resistor that blew up seems to be connected in parallel with the other 2 large grey through hole resistors. Those resistors seems to be connected in parallel with the two large filter caps (450Vdc caps). Can you verify that?

The three resistors are in parallel among them yeah. One side of the resistors connect to the negative of the filter caps and the other goes to a pin of the bridge rectifier labeled as (-) negative.

[budm]

Re: Ilo lct32ha36 dead

That does not make sense at all since the negative of the bridge should be directly connected to the negative legs of those two filter caps. I am trying to trace out the connections but having hard time doing it.

[Beowulf]

Re: Ilo lct32ha36 dead

Call me crazy but I've checked it like ten times visually and using continuity with the meter. I also found it rather strange. It wouldn't be the first time I get a tv with manufacturing defects. I'm anxious to see how the one I ordered is wired up.

Attached is a picture explaining it more.

[budm]

Re: Ilo lct32ha36 dead

How low is the resistance of those resistors, less than 1 Ohm? It may be using that as fusible resistors.

[Beowulf]

Re: Ilo lct32ha36 dead

They're 0.39 Ohms. And they're cracked, probably from that little incident earlier lol.

[budm]

Re: Ilo lct32ha36 dead

For now, it is OK to leave it as is, I do not really know why it has small 1/8W resistor in parallel with the other two large Wattage resistors, since the circuit is not open, the two caps will be charged up OK. I would like to find out if heating those small caps in the standby power supply make it start running again.

[Beowulf]

Re: Ilo lct32ha36 dead

Alright I'll try that tomorrow.

[Beowulf]

Re: Ilo lct32ha36 dead

Alright I tried it like this and put some heat on those little caps and it did not do anything.

[retiredcaps]

Re: Ilo lct32ha36 dead

I'd appreciate any pointer on what to check next.

From PlainBill, I learned there are 3 likely suspects.

1) the startup cap is bad - easy and cheap to replace with a Panasonic FC. I like to keep a stash of 47uF 50V and/or 22uF 50V caps just for these occasions.
2) the SMPS IC is bad
3) something shorted on the output side dragging down the power supply. something like a shorted diode. It would probably only take you 5 minutes to test all the diodes in circuit. If one reads shorted in circuit, desolder to verify readings.

[budm]

Re: Ilo lct32ha36 dead

I would replace those start up caps, they should be replaced anyway so you do not to replace them in the future, it should be part of the cap replacement kit.

[Beowulf]

Re: Ilo lct32ha36 dead

Thanks guys. I'll let you know how it goes when I get down to working on this board again, after I receive the new one.

I'll order some of those caps to keep in stock too.

Regards,