Magnavox 32ME303V/F7

[alja]

Hello, here again kindly asking for help to fix this tv

Model: 32ME303V/F7
Brand : Magnavox
Problem: Steady Stand by light. No sound, no picture.

Pictures as follow from the back of the TV.

Thanks in advance for the help. It's been quite a long time since I don't dive into electronics but last TV I was guided on was a Success so I'm fast learning and follow directions accordingly

[CapLeaker]

Re: Magnavox 32ME303V/F7

sounds like the main board isn't turning on the PSU. Check the PSon.

[ReeceyBurger123]

Re: Magnavox 32ME303V/F7

Do you have a DMM and know how to check for S/C aka short circuit ?

[alja]

Re: Magnavox 32ME303V/F7

I do have a digital multi meter but I'm not sure how to look for the S/C

[alja]

Re: Magnavox 32ME303V/F7

I've tried to test the diodes on the power supply board but I'm not sure if they are right. A site that I looked on said that the diodes should give me a reading only one way and the other way should be OL so some of them were giving me readings both ways .... that means those are bad? how could I know the correct reading I should get from the diodes. I don't really know what I am looking for but it's a start.
This power supply is totally different from the ones I've seen before because I cannot find voltages to measure ... so I don't even know if is the main or the power supply that is bad or both.

any help is well appreciated.

[ReeceyBurger123]

Re: Magnavox 32ME303V/F7

What Ohmage do they give ? Sorry for slow response btw.

[CapLeaker]

Re: Magnavox 32ME303V/F7

So 5V comes from the PSU to the main board. If you press the "On" button, the mainboard returns the PSon signal to the PSU to turn on all power rails. The TV comes on. If that mainboard doesn't send PSon to the PSU, it won't come on. Easy check.

[alja]

Re: Magnavox 32ME303V/F7

What Ohmage do they give ? Sorry for slow response btw.

The ones on top of the transformer from left to right are the ones that don't give me OL

0,28 - 2.8

the ones at the bottom right of the transformer give me

OL - 2,4
OL - 2
OL - 2,5
OL - 1,9

[alja]

Re: Magnavox 32ME303V/F7

So 5V comes from the PSU to the main board. If you press the "On" button, the mainboard returns the PSon signal to the PSU to turn on all power rails. The TV comes on. If that mainboard doesn't send PSon to the PSU, it won't come on. Easy check.

Well that is exactly my problem that I cannot find where to measure those 5V

[CapLeaker]

Re: Magnavox 32ME303V/F7

Everything connected, turn the PSU around so you have access to the back side. Put black probe to GND on the secondary and measure all pins on that ribbon cable that go between PSU and main board. Check each pin and press that power button on the TV on and off. Note everything down. Be careful not to short a pin with a different one with the probe. Also it may not be 5V either.

[ron350]

Re: Magnavox 32ME303V/F7

Alja i don’t think you have to unbolt the power supply just read all of the jumper labels.

[alja]

Re: Magnavox 32ME303V/F7

Thank you CapLeaker, I did what you instructed me and here the values

The power button seems to do nothing, the values don't change when I press the button.

from bottom to top there are 11 pairs and measured

00.0 - 00.0
00.6 - 03.3
00.0 - 03.3
00.0 - 03.3
00.0 - 00.0
00.0 - 00.0
00.0 - 00.0
12.9 - 12.9
12.9 - 12.9
00.0 - 21.0
21.0 - 21.0

[alja]

Re: Magnavox 32ME303V/F7

ron350 I tried but I don't really know what to look for, I measure the ones that says 21v and 3.3 but don't know what else to do.

I forgot to mention that the big capacitor of 330 uF reads 297 uF .... I guess this is not ok? but would it be the culprit?

[budm]

Re: Magnavox 32ME303V/F7

What DCV do you on those jumpers, they are labeled with DCV?
P-ON +21V=
ALL 3.3V =
BL-SW =
PROTECT3 =
AMP+13V =
ADIM P =
Pictures provided by shopjimmy.
http://www.shopjimmy.com/emerson-a3a...pply-unit.htm#

[alja]

Re: Magnavox 32ME303V/F7

Thanks Budm. here the values

P-ON +21V= -0
ALL 3.3V = 3.3
BL-SW = 0
PROTECT3 = 0.6
AMP+13V = 13
ADIM P = -0

[budm]

Re: Magnavox 32ME303V/F7

Thanks Budm. here the values

P-ON +21V= -0
ALL 3.3V = 3.3
BL-SW = 0
PROTECT3 = 0.6
AMP+13V = 13
ADIM P = -0

The power supply is an always on power supply with one transformer to supply all the needed Voltages.
The P-ON +21V is generated by Diode D650, D651 (they are connected in parallel).
The AMP +13V is generated by Diode D653, D655 (they are connected in parallel). The +13V is down converted to +3.3V, 13V is also used for the audio amplifiers.
You must have measurement error because you do have 13V, so the +21V has to be there also (not likely that BOTH Diodes have gone bad) because it is coming from the same power transformer for the +13V, so recheck that +21V again. The +21V is used for running the LED Boosted Voltage LED driver.
The main board is not sending the BL-SW (BL-ON) either.

[alja]

Re: Magnavox 32ME303V/F7

I've checked all the labels and the values are accordingly where says 13v there is 12.98 where says 21v is 21v but only the one you pointed out to me to check, the one next to the connector to the logic board that says "P ON +21v" (J180) is not showing me the 21v the rest of the 21v labels read indeed 21v. I also found the 3.3v where it should be.

Also there is a humming comming from the transformer everytime I energize the board.

And before the tv died it was hard to turn it on but eventually it would until no more.

[alja]

Re: Magnavox 32ME303V/F7

The main board is not sending the BL-SW (BL-ON) either.

I don't really know what this means....

[CapLeaker]

Re: Magnavox 32ME303V/F7

I don't really know what this means....

Means that the backlight behind the LCD screen isn't turned on either. So your screen stays black. That alone tells me that you have a main board problem, as this signal is also generated there like the PSon.

PSon = Power Supply On
BLon = Back Light On

[budm]

Re: Magnavox 32ME303V/F7

So the power supplies are OK then since you do have all the Voltages, but missing the BL-ON signal. You should monitor the BL-ON signal to see if it even change state at all when you turn on the TV.