Memorex MLT3221 no power

[CR Designs]

Have a Memorex 32" tv will not power on set is dead.have checked large cab in center of power suppy board 158v. Checked con3 power is fluctuateing 5vSB 0 to 6v, 5V o to 1v, 12v 0 to 6v. The board is a Proview Ipos 150 Rev 3.3.I know there are some posts on this but there all over the place would like to start this fresh. Thank you for any help.

[budm]

Re: Memorex MLT3221 no power

Look real close at all the caps, especially the ones under the heatsink on the right of the board. What you can also do is to unplug the TV, use the hair dryer to heat up the board for 3-4 minutes, then plug the TV in and monitor the 5VSTBY to see if it becomes stable, it sounds like it has bad start-up cap. The bad part is that you have to remove the hest sink to get to them. They are also known for having 2 bad 10uf 450vdc caps for the inverter section.
http://s807.photobucket.com/albums/y...t=DSC04333.jpg

[CR Designs]

Re: Memorex MLT3221 no power

Heated with hair dryer still voltage is pulsing

[budm]

Re: Memorex MLT3221 no power

You will need to inspect the caps real close, as suggested, the startup cap for the stby5V which is under the heatsink. Do you have ESR meter?

[CR Designs]

Re: Memorex MLT3221 no power

My board doesn't have the 2 cabs you refer to 10uf 450 vdc. see picture of my board. also I have no ESR meter

[budm]

Re: Memorex MLT3221 no power

They use the Poly caps instead.

[CR Designs]

Re: Memorex MLT3221 no power

How do you check them? check like a cap?

[tom66]

Re: Memorex MLT3221 no power

On this model there aren't any known failures with those caps and anyway the TV standby voltage would still be good as they only couple the drive to the inverter transformers.

I see the disc on the main big capacitor (marked 25/105/V46) is bulging, try pressing this down, if you can depress it so it is flat the capacitor is OK, but if you can't then it could be failed.

[CR Designs]

Re: Memorex MLT3221 no power

Can not push it in

[budm]

Re: Memorex MLT3221 no power

The large cap on my board also has domed plastic cap, remove the top, it turns out to be the plastic cap is deformed but the metal cap is flat, you can remove the black disc and see.
It is hard to get to the start up caps since they are mounted under the heat sink. You may be able to fish it through the hestsink hole, you can see it in your pictures. The two caps on my board are lytics type your are Poly type and they are for the inverter circuits, you need to fix the 5CSTBY problem first to see if anything else are bad.
You can also check the DC on that large cap to see if it is fluctuating when the TV is OFF, when TV is on the PFC Voltage booster will kick in, then the voltage will go up to around 380-400vdc.

[CR Designs]

Re: Memorex MLT3221 no power

O.K you lost me on the large cap voltage going up to 380-400 volts. large cap has 185 volts and it does not fluctuate when power is off.

[vinceroger69]

Re: Memorex MLT3221 no power

when you try to turn the tv on does the voltage go up from 185 volts to about 380 volts on the large cap

[budm]

Re: Memorex MLT3221 no power

At this point it will probably not work since the processor does not have steady standby voltage to run the main board circuits. Need to get the stby fixed first.

[CR Designs]

Re: Memorex MLT3221 no power

No it stays at 185 v

[vinceroger69]

Re: Memorex MLT3221 no power

https://www.badcaps.net/forum/showthread.php?t=12886
same power board i think maybe worth a read

[CR Designs]

Re: Memorex MLT3221 no power

budm any ideas how to get the heat sink off this power board. do you de- solder it or will the corners pop off those tabs and un screw the components attached to it.

[CR Designs]

Re: Memorex MLT3221 no power

https://www.badcaps.net/forum/showthread.php?t=12886
same power board i think maybe worth a read

How do you check this diode referred to in the link above? There referring to a diode at D10.

[selldoor]

Re: Memorex MLT3221 no power

You have the advantage that you can see what D 10 looks like? Is it like D5 or D7

[CR Designs]

Re: Memorex MLT3221 no power

Here's picture of diode at D10

[CR Designs]

Re: Memorex MLT3221 no power

Try it again here's the picture of Diode at D10