Sanyo DP32647 Backlight flickering

[coreyand]

So I ended up with a RCA 32" Tv that the p.s. board was shot, and a Sanyo 32" that the screen was broken in the panel. After taking both tvs apart I notice a the inverter board takes the same plug and T-con's are nearly a direct match. So I decided what the heck Ill swap the panels out should work in theory. Anyway after swapping them out I discovered the panel back light turns on for about half a second and then just starts flickering off and on. You can hear noise coming from the inverter board that coensides with the flickering.

Thinking it was a bad swap out I remembered the broken panel did the same thing before I replaced it, to be sure I hooked up the old panel and the same thing is happening.

Im kind of at a loss on what to check, I know it has to be something related to power supply probably but Im not sure what, or where to start.

I did take some voltage readings from the pins going to the mainboard and the inverter board, I get 24v to the inverter where it says I should and 24v, 5v, and 12v going the main board where it says I should. What is there to check next?

Attached is a photo of the of the back of the tv, any insight is helpful. I am eager to learn.

[Ltank]

Re: Sanyo DP32647 Backlight flickering

1st measures the voltage from the P.S. to the inverter (tall board on left of set. The voltage should be stable as labeled. Normally 24vdc. Then check for commands that tell the Backlight to turn on. It too should be a steady voltage. If all is good, remove cover and inspect inverter for burnt parts etc

[truep]

Re: Sanyo DP32647 Backlight flickering

I sold a similar model to a guy after fixing it. He had that problem too. It turned out to be a problem with his line voltage! I bougt it back ang sold it to someone closer to me. Whenever his AC turned on it would start flickering as his voltage had droped to 94 VAC

[tom66]

Re: Sanyo DP32647 Backlight flickering

If the TV has a problem with low line voltage the primary capacitor(s) could be going bad

[coreyand]

Re: Sanyo DP32647 Backlight flickering

Ill take some readings now and post back

Ltank, Would it be possible that both panels have bad inverter boards?

The cracked panel does the same flickering as the replacement which leads me to believe it has something to do with the power supply. Let me get a reading on the voltages again and I will give the exact numbers.

Keep in mind the first time I took readings the voltages were jumping around from the back light flickering off and on. Ill try to get better readings. Ill post back in just a few.

[coreyand]

Re: Sanyo DP32647 Backlight flickering

On the top pin of the ribbon cable, the white one going to the inverter board I get a solid 24.46vdc before the screen turnes on and begins to flash. When its flashing it goes down to 22.30-22.44VDC. I also get around 22.40 VDC from a few of the lines below the first one.

Where would the commands be to turn on the the back light? There is a separate set of wires that comes from the inverter board but instead of going to the power supply they run to the mainboard. Its 3 wires 2 black 1 white.

I tested those separate 3 wires going to the main board.

Here is what they read before I turn the set on

Top(White):.032
Middle (Black): .172
Bottom(Black): .163

And then when I turn it on

Top(white): .028 vdc
Middle(black):4.99 vdc
Bottom(Black):3.35 vdc

On the cable coming from the power supply to the inverter board with the inverter board unplugged I get from top to bottom as shown in the picture starting with the white one:

1. 24.38Vdc
2. 24.38Vdc
3. 24.39Vdc
4. 24.39Vdc
5. 24.38Vdc

On the cable coming from the power supply the main board I get the voltage as shown on the board

Next to 24V : 24.27Vdc
Next to 12V : 11.94Vdc
Next to 5V : 5.05Vdc

Next to PSON( Im guessing this is standby?) 4.85Vdc.

Im thinking that maybe the problem is within the 32 cables coming from the inverter to the mainboard. I think those are my turn on wire perhaps?

I have a panel here very similar, actually the panel that came out of the TV originally that does the exact same thing. However It has an inverter board on it also. Before changing out the inverter board is there any other things to test?

[budm]

Re: Sanyo DP32647 Backlight flickering

Can we see the closed up pictures of the inverter board, especially around the connector that goes back to the power supply board. We need to locate the BL_ON and Dimming control lines.
What is the LCD panel numbers? We can get the spec sheet that will show the pinout of the inverter board.
I am still wondering if the pinout of the two inverter boards are exactly the same.

[coreyand]

Re: Sanyo DP32647 Backlight flickering

Alright I got pictures closer to the inverter board where the p.s. cables come in. Had to take the shield off. Also Is a picture of the panel info. It would be weird if the pinouts for the two inverter boards were different but still present the same problem on both of them. Let me get a picture of the original inverter board.

[coreyand]

Re: Sanyo DP32647 Backlight flickering

Here is a picture of the original inverter board from the original panel.

[budm]

Re: Sanyo DP32647 Backlight flickering

https://www.badcaps.net/forum/attach...2&d=1417842664

ON/OFF is the BL_ON should show steady DC > 2.50V.
E_PWM = External PWM dimming signal.
I_PWM = Internal PWM?

[budm]

Re: Sanyo DP32647 Backlight flickering

Inverter boards pin out

Board #1 pin 11 = ERROR, board #2 pin 11 = DET
Board #1 pin 12 = ON/OFF, board #2 pin 12 = BL_ON
Board #1 pin 13 = I_PWM, board #2 pin 13 = PWM
Board #1 pin 14 = E_PWM, board #2 pin 14 = MODE SEL

So the two boards are not exactly the same, need to find the spec of both panel to understand what those pin 11, 13, and 14 are exactly for.

[coreyand]

Re: Sanyo DP32647 Backlight flickering

Let me check the On/Off, I believe the first three wires being the ON/OFF and the E-PWM and I-PWM are the wires coming not from the power supply but the mainboard that I tested earlier. Ill check them on the inverter board this time.

ON/OFF:.650 VDC
E-PWM:3.35 VDC
I-PWM:4.99 VDC

Granted this is with the set on and flickering so the voltage readings jumped around a little bit.

Should I just try putting the old inverter board from the cracked panel on this one?

[coreyand]

Re: Sanyo DP32647 Backlight flickering

Without turning on power the ON/OFF reads out 2.20VDC and climbs up slowly. I think ill try swapping the inverter boards and just see what happens. Unless you think thats a bad idea, do you think it would cause damage to the panel or bulbs?

Actually that wont work. Theres 8 leads off the inverter that goes to this panel and only 7 leads from the inverter board from the other panel. Let me see if I can dig up some specs on these boards.

[budm]

Re: Sanyo DP32647 Backlight flickering

Spec of the V315B1-L01 V2

"ON/OFF:.650 VDC
E-PWM:3.35 VDC
I-PWM:4.99 VDC"

Are you sure you are measuring at the correct pins, especially the ON/OFF pin? min DC Voltage on this pin for backlights on is 2V (5V MAX).
Another important one is the supply voltage for the T-CON board, this one uses 5V, most of the 32" uses 12V, so the pinout of the T-CON will have to be verified also or bad damage will result in T-CON and on the main board.
It always best to verify the pinout, the voltage, current requirement, etc.
Boards that are using the same connectors do not mean they are the same.

[coreyand]

Re: Sanyo DP32647 Backlight flickering

When tv is plugged in and turned of I get 2.40 VDC to the ON/OFF lead on the inverter board. The TCON on this panel is off the old panel. The ribbon cables matched up to it.

[coreyand]

Re: Sanyo DP32647 Backlight flickering

Without turning on power the ON/OFF reads out 2.20VDC and climbs up slowly. I think ill try swapping the inverter boards and just see what happens. Unless you think thats a bad idea, do you think it would cause damage to the panel or bulbs?

Actually that wont work. Theres 8 leads off the inverter that goes to this panel and only 7 leads from the inverter board from the other panel. Let me see if I can dig up some specs on these boards.

Yeah about 2.20V to 2.40V on the ON/OFF

[budm]

Re: Sanyo DP32647 Backlight flickering

Yeah about 2.20V to 2.40V on the ON/OFF

OK, I thought you were getting only 0.65V

[budm]

Re: Sanyo DP32647 Backlight flickering

BTW, according to page 15 of the spec sheet:
#PIN 13:Analog Dimming Control (Use Pin 13) : 0V~3.3V and Pin 14 must open.
#PIN 14:PWM Dimming Control (Use Pin 14) : Pin 13 must open.
#Pin 13(I_PWM) and Pin 14(E_PWM) can not open in same period.

I have no idea what is the setup being used in the original chassis and the one you are trying to use the in.
Is the other panel is also CHI MEI?

[coreyand]

Re: Sanyo DP32647 Backlight flickering

budm, Could this be a problem elsewhere maybe? The original panel when hooked up does the same thing with the blacklight flashing off and on over and over. Here is the original panel picture attached.

[coreyand]

Re: Sanyo DP32647 Backlight flickering

OK, I thought you were getting only 0.65V

Thats when the set is powered on, the 2.4v reading is when it is turned off.