Panasonic TX-49DX600B Dead! TNPA6232 Power Board

[baddesley]

Hi everyone, I have just acquired this Panasonic TX-49DX600B 4K HDTV, which is to all intents and purposes totally dead. There is no power LED, no picture or screen brightness, no sound, nor any response to the remote control.

However, there is power on the TNPA6232 power board, mains in, high voltage on the main caps (450V, rising to 600 odd volts - and the caps are only rated at 450V!) and 80V rising to 100V and 18V rising to 24V on the top centre caps. Inititally, the voltages are at the lower figures, then after a minute or so, the higher voltages can be measured, but the TV still fails to show any signs, or respond to the remote control. I daren't leave it on very long, as the main caps will likely blow!

Does anyone have any experience of these, any known/common failures, known voltages to check, or a circuit diagram? Any help much appreciated, thanks.

[Quaddro]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

High voltage in bulk/main capacitor can be cause of something wrong in apfc section.
Usually pfc controller ic.

what is under the (white) heatsink?

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

Hi Quaddro, I'm not sure which heatsink you mean, they are all metal and only look silver, or a bit white, depending on how the light is reflecting off of them. I have now numbered the heatsinks in this new photo though.
However, all of the devices under the heatsinks are three-legged devices, so possibly the control device is on the main board? I would expect a contol IC to have at least four pins!

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

It looks like the power control IC could be the small-ish one on the reverse side, near the middle. There's no sign of any blow-out damage, though it could of course just be malfunctioning, but without any voltages to check, this is just a guess. Anybody got any knowledge of these sets and boards before I just order a new power board and cross my fingers?

[R_J]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

What are you using for ground when measuring the primary caps voltage?

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

Straight across the caps themselves.

[R_J]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

It could be your meter, some meters don't like the high frequency of the pfc circuit, have you checked if you have any of the standby voltages like SRV-5V
Also what is the voltage on SUB_ON
It could also be your meter battery is low causing the wrong voltage readings

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

Thanks RJ. I don't think it's my meter, as I've not had problems like that with it before, but it could be that. As I'm measuring across the main caps themselves and because the voltages increase shortly after powering up, I think the voltages are correct, but I'll bear it in mind, as they are ridiculously high, even at first power up, if they are correct!

I've not measured any other voltages yet, due to the worry of leaving it powered up for too long with such high voltages (maybe) across the primary caps.

On closer inspection, I see that there are a few voltages marked, both on the power board and on the main/signals board, so I'll check them out in a while and will post what I find.

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

OK, well I've measured the marked voltages, though I'm not sure how helpful it will be. Maybe my meter isn't measuring accurately, but for the record, the marked voltages measure as follows (with respect to a point marked 'ground') on the 'cold' side.

64V (marked) measures 90V
16V (marked) measures 20V
5V (marked) measures 8.5V
SUN On measures 4V

Maybe there's nothing wrong with the power board after all and it's just my meter and maybe the main board isn't functioning - the IR receiver and power LED come off of this board, so could be stopping it from switching on(?).

But all of these voltages are varying. Whether that's because of the fault, or my meter, I just don't know. What I really could do with is a circuit diagram.

[R_J]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

The SUB_ON would be the power supply on signal from the main board, It turns on the power supply, If the tv was in the OFF state this voltage should be near 0 volts.
All your voltage readings seem to be out the same 25~30%
Type this into your search engine "tnpa6232 service manual"

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

Great, thanks RJ. Yes, I agree, all of my voltages are measing the same amount out, so maybe it is my meter, though I would have thought the SUB On would have been above 5V by the same amount as well, but maybe I'm wrong there - I've got the circuit diagram for the power board now, thank you very much, so I'll be able to check.

I did search for one, but it all depends on the exact words used doesn't it! Anyway I'll have a good look at that and see where that takes me and will post back tomorrow on how I get on.

Many thanks for now!

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

OK, well I think I'm getting somewhere now. Having had a look at the power board circuit diagram, it was clear that my meter WAS reading highly inaccurately (thanks RJ), as the primary caps are directly across a mains bridge rectifier, so my meter was clearly wrong! I've only ever fixed a couple of these types of sets before, so I hadn't assumed this to be the case, but I'm guessing it probably is.

Anyway, I replaced the battery in my meter and re-tested all of the PS voltages and guess what - they were all a LOT lower and stable! My primary voltage is now 387V, as it should be and the 64V, 16V and 5V supply rails are also correct.

Power_ON going out from the PS to the main board changes when I press the power button on the PS board, but SUB_ON coming back from the main board is 2.4V and doesn't change.

I've got a bit more checking to do, but it's looking like my power board is probably fine (bit strange that all the supply volts are up and OK though) and the problem is likely to be on my main/signals board, but I'm going to do a few more checks before I shell out for a new one, as they are not exacly cheap and I don't like changing boards unless I have to.

I'll update this once I have done some more checks, or got a new board (may be several days) but thanks again, any other suggestions are more than welcome in the meantime.

Either way, I'll let you know what the problem is, if I manage to fix it (don't you just hate it when people just say, 'it's fixed now, thanks' and don't tell you what it was!)

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

Well, I'm pretty convinced it's the main/signals board, it looks like the main processor chip IC8000 has failed - no 12V or SUB_ON outputs, whereas everything coming in looks OK. Only a new board now will prove if I'm right or not.

I did find a write-up (originally in Polish/translated: https://www.elektroda.pl/rtvforum/topic3623194.html) about one of these sets with a failed backlight causing no picture or sound, but that had a pulsing fault code on the TV Power LED (as it should do). Mine has nothing at all on the LED, totally black, despite the LED circuit having power, so I don't think that is very likely and I don't really want to pull the whole set apart to check it.

The problem is, the main boards are coded to work with specific screens, so I need a TNPH1160 with the TNX/A1LVVB code (marked with a sticker in the CA slot) and these seem to be impossible to find. There are some suppliers with them listed, but all the ones I've found are out of stock, so I've signed up for availability notifications, but until I can find one - at a reasonable price - I'm stuck. Anyone know where to get one from (there are none currently on ebay either)?

[diif]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

No 12v ? What is IC800 ? Why not replace it ?

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

The 12V I'm talking about is generated internally from the main 16V line by IC8000, a large BGA mounted processor type IC. To replace it would need specialist surface-mount soldering and de-soldering equipment, which I don't have.

I have tried re-soldering/replacing these in the past using a standard heat gun and some home-made shielding, but with no luck. Doing this often results in other bits coming of the board and soldering a new one on the board is definitely a skilled job needing the correct tools (I know, I used to work in digital TV and we had specialist guys and equiment for this). It just isn't worth trying. I did try heating it up, just to see if I could fix any poor joints, but it made no diference.

This description gives an idea of how the circuit works (https://www.manualslib.com/manual/14...-Lcd-2016.html), but I've still not been able to find a circuit diagram for the main board, so my only option really is to find a new board.

[diif]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

Yes, I asked what IC8000 was to check the availability, I have a rework station.

As R_J has pointed out, you have SUB_ON. It seems it's just the 12v missing, IC8000 won't be dropping 16v to 12v, I'd investigate the device that does.

Have you done the troubleshooting on page 39 ?

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

Hi Diff, thanks for your interest and help. IC8000 is a Mediatek MT5810PEHJ (see photo). This is available for around £25 or so (not in this country though, as far as I can see), but as you say, this is not necessarily the actual cause of the problem anyway.

You're right, this chip doesn't drop the 16V line to 12V itself, it switches it via another chip. According to the description, this is IC5500 (or IC5300 according to one of the drawings!). Having looked at the board very closely, many times though, there is no IC5500 or 5300, they just don't exist.

The likely candidate is actually IC5704, an LD1117AG, which is a low-drop voltage regulator which is locate on the back of the board. I don’t know that this is the right chip, but there’s a chance that it is. I’ve not measured the voltages on this as yet (what with it being on the back of the board), but as all of the connections are on the left side, I should be able to find a way to prop the whole board out somehow to get to the back of it and do this. I'll give that a go tomorrow, if I have time.

No, I haven't gone through the full voltage level checks as per page 39, but have done some checks around that area. I don't have a 'scope or logic analyser, only a multimeter, so I’m not sure if I would be able to see all of these changes, certainly not the timings anyway. I might give it a go at some point, but I’m not sure it will be of much help. I did go through the flowchart diagnostics on the other pages, but that just tells me to 'change board A' (main board).

Anyway, thanks again, I’ll try to take another look at this and try to measure the voltages on the regulator (if it's the right one) tomorrow and will update this then.

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

Right, having finally got round to measuring voltages around IC5704, it is clearly not the 12V regulator. However, I have found that this TV uses the LA64 chassis and have found a couple of circuit diagrams for other models that uses the same chassis ( and https://www.electronica-pt.com/esque...sis-la64-66216).

Not exactly the right manuals, but good enough and I can see that IC 5260 is the 12V regulator on the main board. This has power coming in, but no control voltage from IC8000. As the SUB_ON also comes from IC8000 and is not changing and the Red LED output also comes from IC 8000 and is not coming on, I am even more convinced that this is the cause of the problem, especially as all other start-up voltages seem to be OK.

Unfortunately, the correct main board for this model and screen is simply not available at the moment (not that I can find anyway), so it looks like I'm just going to have to wait until I can find one and hope that does indeed fix it.

Thanks again to everyone for their input. I hope the circuits etc., are helpful to someone else. I will post back if and when I get a new board, or find anything else.

[baddesley]

Re: Panasonic TX-49DX600B Dead! TNPA6232 Power Board

I finally managed to get a new main board for this TV and it has fixed it! I now have a brilliant, fully working TV. As far as I can tell, the fault was with IC8000, but I can't confirm that of course. The indications that it was faulty were the missing 12V line, no change of SUB_ON when pressing the on/off button and no indication whatsoever on the front Red LED. Hope this helps someone else and thanks for everyone's input.