Panasonic 65" VT20 10 blink code

[infrag]

Re: Panasonic 65" VT20 10 blink code

I have gone around this board IC by IC comparing voltages to the working board I have as reference. I cant for the life of me figure out what chip/voltage is not being produced. Everything I can find is identical or close enough not to be an issue. I've compared voltages on the connectors and they are the same. I've got a whole bunch of IC's that I've compared leg by leg and they are the same. I havent tried the back of the board yet as thats harder to do plugged in...

Anyone got any pointers or experience with this kinda thing?

I'm probably wasting my time on this but I'm waiting for a guy over east to pull apart his TV this weekend and send the parts over so I figure I've got nothing to lose by trying to compare/repair this board.

Even if I find the part thats wrong with it I'd be happier

[infrag]

Re: Panasonic 65" VT20 10 blink code

not right now, maybe tomorrow evening plus it's screwed together. Time for some zzzzzzzzzzzzzzzz s

Any chance you'll have time to do it on the weekend?

[tn245]

Re: Panasonic 65" VT20 10 blink code

I spent quite a bit of time chasing down a 10 blink on a GT20 board recently. 10 blinks is the same SOS on that board.

SOS is: Sub 5V, Sub 3.3V, Sub 9V, Tuner Power, MIHO 3.3V, LED 8V.

Went through the service manual finding each point to test on the schematics and then finding the relevant point on the PCB map further down. Sorry I didn't keep a note of where each point is. Quite a few of the points are on the back of the board. I found I could support it with one hand and test with the other to get at the back of the board. I had all those voltages except for MIHO and LED but looking through the schematics those voltages would not appear unless the panel on signal was generated at the MPU which didn't seem to be happening. I didn't get any further with it sadly but would be interested if you do.

Maybe check out IC5811 - 8 pin ic on the top side, toward the left edge near to connector A20. Pin 4 should tell you if you're getting PANEL_STBY_ON, then the bottom side of L5814 inductor just below it should be your MIHO 3.3V.

[tw2005]

Re: Panasonic 65" VT20 10 blink code

Can you test on the bezel the resistance from the surface of the EMI strip to the frame its stuck to? Does the resistance change if you push harder on the surface of the EMI strip?

I did not notice but about 2 ohms

[infrag]

Re: Panasonic 65" VT20 10 blink code

I spent quite a bit of time chasing down a 10 blink on a GT20 board recently. 10 blinks is the same SOS on that board.

SOS is: Sub 5V, Sub 3.3V, Sub 9V, Tuner Power, MIHO 3.3V, LED 8V.

Went through the service manual finding each point to test on the schematics and then finding the relevant point on the PCB map further down. Sorry I didn't keep a note of where each point is. Quite a few of the points are on the back of the board. I found I could support it with one hand and test with the other to get at the back of the board. I had all those voltages except for MIHO and LED but looking through the schematics those voltages would not appear unless the panel on signal was generated at the MPU which didn't seem to be happening. I didn't get any further with it sadly but would be interested if you do.

Maybe check out IC5811 - 8 pin ic on the top side, toward the left edge near to connector A20. Pin 4 should tell you if you're getting PANEL_STBY_ON, then the bottom side of L5814 inductor just below it should be your MIHO 3.3V.

IC5811 was the IC located higher up the board.
IC5808 is the one near connector A20.
I've checked it out on the bad board and good board and finally I've found some differences in voltage. Thanks!

Bad board pin:
1. 0.8V
2. Starts higher but drops off before I can get a reading so ?
3. ?
4. 3.27
5. 0.6
6. ?
7. 5.2
8. 15.89

Good board pin:
1. 0
2. 8
3. 12.75
4. 3.27
5. 0.8
6. 5.1
7. 5.2
8. 15.89

So yes I seem to get panel on but I have a problem with LED 8V at least.

[infrag]

Re: Panasonic 65" VT20 10 blink code

Out of interest did you fix your board? If so what part(s) were broken?
Do the IC's normally fail or the supporting parts nearby them on these things?

[infrag]

Re: Panasonic 65" VT20 10 blink code

Double post

[infrag]

Re: Panasonic 65" VT20 10 blink code

Checked all the test points. The 6v led point is the only one not coming through. Can't find the faulty part around it so I guess I'll have to assume its the IC? Can I bypass it put a separate 6v power supply on it to test?

[tn245]

Re: Panasonic 65" VT20 10 blink code

To be honest I'm just poking around in the dark same as you. I didn't manage to fix my board yet. On mine I'm suspecting either something up with the gpu or the software. It was a board from a cracked screen TV and arrived wrapped in plastic cling film so maybe static damage?

Your board's got a bit more to go on I think. Was on the wrong service manual previously but got the right one now. You're getting the panel on signal but LED 6V (or 8V? - they seem confused in the manual) is missing potentially causing the 10 blinks sos.

Do you have everything hooked up and measuring the same way when testing both boards? I'm wondering why you've got 0.8V on a gnd pin (pin 1).

Datasheet for the ic is here assuming same as on my board:
https://www.digchip.com/datasheets/p...S-Z-LF-pdf.php

The IC could be bad but also could be other components around it or even further down the line. Shorted ceramic caps are reasonably common. You could compare resistance readings to gnd on the pins of the ic. Maybe others with more knowledge can help interpret what's going on based on the datasheet for the ic.

[tn245]

Re: Panasonic 65" VT20 10 blink code

What's the resistance between pin 2 and gnd on both boards?

[budwich]

Re: Panasonic 65" VT20 10 blink code

IF the datasheet / ic is the same as provided, the pin (5) in question is an "input" to the ic so you need to trace the tracks along the way to find out where its getting that info. Possibly a broken trace or a burnt resistor.

forget this...
As suggested by tn245, check your grounding measurements as the voltage measured there seems out of place. Interesting that you seem to be having "issues" with two sets in and around grounding and the like. :-(

I would check all the capacitors around this ic. Your pin 3 is also suspect ... the "?" means what?

[infrag]

Re: Panasonic 65" VT20 10 blink code

The ? Means the voltage goes up for a split second and drops off before I can get a reading. My assumption is its because there is either a short or over voltage condition somewhere along the line. Or the ic is stuffed or both.

The earth pin I'll remeasure. The probe might not have been on 100% . I measured the pins before I knew what they were all meant to be...

As for the input pin idea I could cut the trace and put 0.8v on it like the other board or not a good idea?

[infrag]

Re: Panasonic 65" VT20 10 blink code

Unfortunately I don't have an ESR meter yet. Its still on the way...
This means I can only check to see if the caps aren't shorted or have a guess at someone of them and hope I don't wreck them taking them off and back on again to check capacitance.

Basic checks there are no shorts there that I can see. Might be the other side of the board but so far I'm at a dead end.

[infrag]

Re: Panasonic 65" VT20 10 blink code

Well I've been a bit of a barbarian and tried my idea of putting some stable voltage on the input pin 5 (or what I assume it is from budwich's comment previously)

I tried with 0.6V but it didnt like that so i tried lower. I put 0.2V on it and tried turning the set on. Made a bit of a squeaky noise but the set did turn on!

So now I guess I should check why that voltage isnt stable on it own in circuit...

[budwich]

Re: Panasonic 65" VT20 10 blink code

hmmm... not sure where you are at with this. was this "pin 5 test" with the good board or the bad board? Further, if it was the bad, did you measure the other voltages? I think by lowering the FB (pin 5)... if I read the sheet, it lowers the frequency of the "chopper" and thus it might now be in your audible. Not that it means much other than, at the higher frequency, the thing doesn't appear to work.

looking further at the "spec" (if it is the right one), if you can find the zener diode on the output of two and check it... maybe its bad / breaking down.

[infrag]

Re: Panasonic 65" VT20 10 blink code

I did my pin 5 test with my bad board. I couldn't at the time check the other voltage while I was doing this.

Thanks for the feedback. I'll check it now.

[infrag]

Re: Panasonic 65" VT20 10 blink code

Excuse my ignorance but is there a way to test the diode in circuit?
I realise I could check voltages on the pins when its on but since its only on for a split second before voltage drops how can I check this?

I've tried removing the diode from the board but its been a pig and I feel if i try anymore I'll wreck it.

I do have some non surface mount diodes lying around but I have no idea what specs they need to have if I had to replace it.

[infrag]

Re: Panasonic 65" VT20 10 blink code

well it doesnt appear to be the diode. I've tested it and it appears OK. Tried a replacement and that does the same thing anyway.

[infrag]

Re: Panasonic 65" VT20 10 blink code

OK I gave the bad board 0.1V on pin 5 again.
The voltages then are stable (for the brief moment I let it stay on as they are obviously wrong)

1. 0V (Ground)
2. 11.47V (too high should be 8V)
3. 15.4V
4. 3.3
5. 0.1V (I didnt check this pin if it ended up higher or not)
6. 0V
7. 5V
8. 15.89

The TV turns on like this but I dont want to leave it on with 11.47 instead of 8V.

I might see if I can make up a separate circuit from pin 5 to pin 2 as described in the IC datasheet.
Maybe something is dragging it down so its not getting the input it needs.

[infrag]

Re: Panasonic 65" VT20 10 blink code

Well I tried a bit more experimenting but everything seems OK.

If I put 8V on pin 2 output everything works. I do have to wait till the IC tries and fails to start itself otherwise it goes ballistic and starts outputting 14.5V which is dangerous I guess.

Anyway I turn the TV on... wait for the IC to try and start and give up. Then give it 8V from external powersupply. Everything is happy and hardly and power draw from the powersupply.

The IC voltages are then:

1. 0
2. 8
3. 12.75
4. 3.27
5. 0.8
6. 5.1
7. 5.2
8. 15.89

So everything seems happy and the TV runs sweet.
I checked the service menu and it reckon the TV power on time is 222 and turned on and off 192 .

Anyway does it make sense then that this IC is just stuffed or maybe its too sensitive in detecting a short?