Panasonic TX-48CX400B - No Video

[nomoresonys]

Re: Panasonic TX-48CX400B - No Video

Ok, so I got another t-con board, but I have the same issues as before, sound but no picture.

Testing the voltages on the new t-con board, I'm seeing more or less (+/- 0.03V) the same voltages as noted a few posts above.

I went back to the power board, at the connection (CN4) that goes to the mainboard, and apparently I'm not getting what I think should be the +5V_STBY, this is what I'm getting on the pins (hope I've assigned the voltage to the correct pin)...

1 24.8V
2 0.01V
3. 0V
4. 0V
5. 3.2V
6. 0V
7. 1.6V
8. 0V
9. 0V
10. 11.8V
11. 11.8V
12. 11.8V

I've attached the 071114 R9 schematic, but it doesn't show the CN4 pinout, I got the CN4 pinout from the R6 schematic, so assuming it would be the same.

But the mainboard would be using 5V standby for generating video, would it, surely it would be using the 12V?

Do the pins have a name beside them?

[tmcw]

Re: Panasonic TX-48CX400B - No Video

Do the pins have a name beside them?

No, they don't, I deduced which was pin 1 etc., based on the R6 schematic showing pins 10, 11 and 12 being 12V, and then working from there to fill in the rest. I also saw another poster saying the same thing here, post #10...

https://www.badcaps.net/forum/showth...hlight=17IPS20

I've attached close-ups of both sides of the connector, but you can see that there is no markings to tell which is pin 1.

From the R6 schematic document, the pins are labelled as follows...

1. PIN_1
2. -| (Earth?)
3. ST_BY
4. -| (Earth?)
5. BL_ON-OFF
6. -| (Earth?)
7. PWM_DIM
8. -| (Earth?)
9. +5V_STBY
10. +12VCC_S
11. +12VCC_S
12. +12VCC_S

And I'm getting...

1 24.8V
2 0.01V
3. 0V
4. 0V
5. 3.2V
6. 0V
7. 1.6V
8. 0V
9. 0V
10. 11.8V
11. 11.8V
12. 11.8V

[diif]

Re: Panasonic TX-48CX400B - No Video

Looking at the schematic, Q212 is the 5V standby regulation.

[nomoresonys]

Re: Panasonic TX-48CX400B - No Video

Don't know if you already tried or not but did you see if you have the 5 volt stndby with the cable from powerboard to mainboard unhooked?

[tmcw]

Re: Panasonic TX-48CX400B - No Video

Don't know if you already tried or not but did you see if you have the 5 volt stndby with the cable from powerboard to mainboard unhooked?

Just tried that now...

With the powerboard to mainboard cable disconnected, I still see zero volts on the 5V standby.

But I notice that the 11.8V and 24.8V on the other pins are still there.

I'm far from an expert, but I thought that these power supplies were designed to keep the higher voltage circuits disabled until the set was turned on, and that the 5V was needed to allow the set come out of standby, and which point the other voltages would be activated.

[nomoresonys]

Re: Panasonic TX-48CX400B - No Video

Check the trace and see where your stndby pin/s are going.

[nomoresonys]

Re: Panasonic TX-48CX400B - No Video

It seems strange that it looks like you have 2 labeled standby with no voltage on either.

[budm]

Re: Panasonic TX-48CX400B - No Video

1) If you look at the schematic, the ST_BY (PS-ON) pin is ACTIVE LOW (Q206 is the controller), you should see this line toggle high when TV is turned off.
2) Looking at your PCBA, it does not look like the 5VSTBY section is stuffed with parts.
3) The fact that the new T-CON board you have
VIN_12V ... 11.78 ... 11.82
but still no HVIN_12V ... 0.06 ... 0.06

[budm]

Re: Panasonic TX-48CX400B - No Video

T-CON training.
See how HVIN_12V is generated.

[nomoresonys]

Re: Panasonic TX-48CX400B - No Video

Thanks Bud, this will help many many of us.

[DanSpangles]

Re: Panasonic TX-48CX400B - No Video

Hello

Did you manage to solve this issue? I have exactly same issue on same model. Replaced all boards and still no voltage on HVIN on tcon. Any solution?

Many thanks

[DanSpangles]

Re: Panasonic TX-48CX400B - No Video

I will add that when I'm testing voltages I place my black lead on the casing and it shows 3v. Is this normal as it hasn't happened on any other TV I have looked at? When I placed the red lead on a ground point it goes to 0v. Just wondered if there was a short causing the issue.

Thanks

[tmcw]

Re: Panasonic TX-48CX400B - No Video

I've just seen your post here...

No, I never got any further with it, gave up, and put the TV into storage. May come back to it.

[dick_barton]

Re: Panasonic TX-48CX400B - No Video

If Q212 is not in circuit then there will be no +5V_STBY