RCA L32WD22 no picture

[rossland]

Hi, my TV quit while I was plugging in a HDMI cable (just coincidence?) The LED turns green, but no picture, sound, etc...can't bring up menu..nothing. When I turn it off the LED flashes amber 23 times. The voltages on the power supply check out .. 5v, 15v, but the 12v reads high at 14v. All caps are visually OK, nothing burnt. Same with main board. Any suggestions?

[selldoor]

Re: RCA L32WD22 no picture

Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back (in the same orientation) and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed

https://www.badcaps.net/forum/attach...7&d=1280167246

https://www.badcaps.net/forum/attach...6&d=1280167246

https://www.badcaps.net/forum/attach...4&d=1280167246

It will be useful if you can say a bit about yourself - skills tools etc.

[rossland]

Re: RCA L32WD22 no picture

Thanks for your help. Hope these pictures are helpful. I am no expert by any means, and this is my first TV repair. I am pretty good at soldering, and have repaired other electronics. I have a few DMMs, and a scope. I forgot to mention in my last post that my 24v was also high at 27v.
C

[rossland]

Re: RCA L32WD22 no picture

I had another go with the power supply board. Everything looks good with the exception of the 12 and 24 volt legs running too high. Is this acceptable? I'll check out the main board tonight.

[budm]

Re: RCA L32WD22 no picture

Can you take the pictures of the Inverter board/s? We need to see the BL_ON (ON/OFF) PIN which turn the backligts inverter circuit on/off.

[ben7]

Re: RCA L32WD22 no picture

The 14v on 12v, and the 27v on the 24v does not seem right. Those caps in there look to be made by 'Elite', which of course is crap. Have you tested the voltages on the voltage regulators on the mainboard? They look like big transistors (they have 3 pins, and one tab. Usually one pin is cut off, however that does not affect operation, since the tab is used instead of that pin).

Also, is this an LCD or an LED TV???

[retiredcaps]

Re: RCA L32WD22 no picture

The 14v on 12v, and the 27v on the 24v does not seem right.

On most lcd and TV SMPS, the voltage rails are typically unregulated. They will run high until there is a load (i.e. the TV is working with a picture and backlight).

[tom66]

Re: RCA L32WD22 no picture

And, on most DMMs, with a flat battery, readings will appear higher than they actually are.
Most inverters will actually shut down with 27V on the 24V. Typically rated from 23V to 26V DC.

[retiredcaps]

Re: RCA L32WD22 no picture

And, on most DMMs, with a flat battery, readings will appear higher than they actually are.

Yes, about once a month, we see cheap multimeters give incorrect readings with weak batteries, but with no indication of a low battery indicator on the lcd display.

[retiredcaps]

Re: RCA L32WD22 no picture

I also dislike it when people don't post the exact reading.

For example, is the reading 27V? If yes, that would imply it is 27.00V exactly. Or is 26.88V, but rounded up to 27V?

Unless you are using an analog multimeter, please report all digits on the multimeter.

[rossland]

Re: RCA L32WD22 no picture

Thank you for the advice. I will replace my battery and re measure the voltages. I uploaded a couple more pics showing the connections. I have voltage going to the Darfon board, but it doesn't turn on. What kind of signal does it need on the on/off pin... grounded, or a voltage ? Wish I could find a more useful service manual.

[rossland]

Re: RCA L32WD22 no picture

After changing the battery, I got some readings that make sense...

5volt = 5.26 standby, 5.19 switched on
15volt = 15.01v
24volt = 24.01v
Now the 12 volt ... 13.54v on standby (should this have voltage on standby?) 13.47 switched on.
I think its safe to say that the 12 volt is too high. Could this be the cause of my problems? I checked the main board too. All the voltages at the regulators are within spec, as printed on the board.
Also, the 5 volt is a bit high, is this a problem?

[ben7]

Re: RCA L32WD22 no picture

After changing the battery, I got some readings that make sense...

5volt = 5.26 standby, 5.19 switched on
15volt = 15.01v
24volt = 24.01v
Now the 12 volt ... 13.54v on standby (should this have voltage on standby?) 13.47 switched on.
I think its safe to say that the 12 volt is too high. Could this be the cause of my problems? I checked the main board too. All the voltages at the regulators are within spec, as printed on the board.
Also, the 5 volt is a bit high, is this a problem?

If there is barely any load on it, then the output will be high. Just like in linear unregulated power supplies. No, I do not think this is your problem.

[retiredcaps]

Re: RCA L32WD22 no picture

Can you take the pictures of the Inverter board/s?

Budm asked for pictures of the inverter boards. I don't see them.

[budm]

Re: RCA L32WD22 no picture

"All the voltages at the regulators are within spec, as printed on the board" I do not see any Voltage rating printed on the board by the Low Drop Out Voltage regulator ICs. The less info we get from you the less help you will get.

[rossland]

Re: RCA L32WD22 no picture

Sorry guys, I'm new to this. More pics to come. The inverter board? Is that the one for the backlight?

[retiredcaps]

Re: RCA L32WD22 no picture

The inverter board? Is that the one for the backlight?

Yes.

[rossland]

Re: RCA L32WD22 no picture

More pics. I've included the values printed on the PCb for the regulators.

[budm]

Re: RCA L32WD22 no picture

OK, I see three small LDO Regulators but do not see any Voltage printing next to them that I can easily see in the pictures.
I also see fuses on the inverter board that need to be checked.
I also need good focus picture around the area of the inverter board connector, I cannot see anything printing on the board that shows the function of each pin of the connector. We need to find the BL_ON/INV_ON/ONOFF PIN.

[rossland]

Re: RCA L32WD22 no picture

Thanks budm. The LDO regulators you circled are all marked as "7E7L 17-33L" They measured as follows...
LDO #1 Pin1 5.4mv Pin2 3.28v pin3 5.02v
LDO #2 Pin1 4.3mv Pin2 3.33v pin3 5.02v
LDO #3 Pin1 5.5mv Pin2 3.30v pin3 5.02v

On the inverter board, 2 of the fuses read 0 ohms, but fuse 1 read 1.8 ohms.
I've included a pic of the back of the inverter board that has the pin functions.
The voltages at the cable (not plugged into the inverter board) are..
Pins 1-5 (VDD) 24.07v
pins 6-10 (GND) -40.01mv
pin 11 -not used-
pin 12 (BL ON) 0.85v
pin 13 (VDIM) 9.9mv
pin14 -not used-