panasonic tx-p50x50b

[sordids999]

hello

got this tv today im hoping its the TCZAA6755U Chip U203 have been told it keeps turning on intermittently but dead at the moment so ill proberly order one but any checks to try also ?

thanks

[drussell]

Re: panasonic tx-p50x50b

got this tv today im hoping its the TCZAA6755U Chip U203 have been told it keeps turning on intermittently but dead at the moment so ill proberly order one but any checks to try also ?

If it has no 5v standby power, I would highly suspect the 6755 on sets with one controlling the standby power.

You should be able to power it up by using an external, isolated, 5v power supply to supply the 5v standby power. Even a moderate sized, charged-to-5v capacitor touched to the standby power pin and ground on the PSU output connector may well bring it out of it's slumber as the problem seems to usually be with the priming and startup on the 6755. The 6755 is connected directly to the rectified DC from the mains and starts itself with a small capacitor charging current. At first I suspected one of the caps on the 5v standby was too leaky for it to charge enough but, nope, it was the chip itself.

Once it actually gets up to standby power, the set should work fine.

[tom66]

Re: panasonic tx-p50x50b

Check JP67 for 5V standby

[sordids999]

Re: panasonic tx-p50x50b

ok same thing tom black on chassis red on JP67 ?

Also is that the correct part i need ?

http://www.ebay.co.uk/itm/2616982750...%3AMEBIDX%3AIT

[tom66]

Re: panasonic tx-p50x50b

Yes to (1)... and maybe... not sure, best to check on your board.

[sordids999]

Re: panasonic tx-p50x50b

no 5v standby and from what i can tell the part has PC3AK 6755U wrote on it so the one on ebay should be fine ?

[tom66]

Re: panasonic tx-p50x50b

Should be ok then

[piccy]

Re: panasonic tx-p50x50b

Have same set , my problem is 7 blinking lights , could it still be the TCZAA6755U chip,
i have 5v on jp67 but there appears to be no readings on jp79 or jp82

does this point to the vsus board or still psu
how do i ensure vsus board is discharged before looking at it ,

i have looked round the fets and there seems to be a few heat affected solder joints on the pins of one or two of them q601 and q401

does the white ribbon cable and screen ribbon cables just require gently pulling out or are there clips

thanks

[tw2005]

Re: panasonic tx-p50x50b

Have same set , my problem is 7 blinking lights , could it still be the TCZAA6755U chip,
i have 5v on jp67 but there appears to be no readings on jp79 or jp82

does this point to the vsus board or still psu
how do i ensure vsus board is discharged before looking at it ,

i have looked round the fets and there seems to be a few heat affected solder joints on the pins of one or two of them q601 and q401

does the white ribbon cable and screen ribbon cables just require gently pulling out or are there clips

thanks

for the ribbons you need to lift the latch, then gently pull out, for the SN20, lift latch and if you lift the ribbon it should just come out. there's a couple of tabs on the sides of that one.

7 blink normally would be SN board I'd expect. The 6755U IC is more to do with a dead set, no standby voltage, no life at all. You don't have that problem if 5v is present and you have error blinks.

Not sure what goes on these, if you have a meter check the heatsinked transistors for shorts.

[Nicholas]

Re: panasonic tx-p50x50b

If it has no 5v standby power, I would highly suspect the 6755 on sets with one controlling the standby power.

You should be able to power it up by using an external, isolated, 5v power supply to supply the 5v standby power. Even a moderate sized, charged-to-5v capacitor touched to the standby power pin and ground on the PSU output connector may well bring it out of it's slumber as the problem seems to usually be with the priming and startup on the 6755. The 6755 is connected directly to the rectified DC from the mains and starts itself with a small capacitor charging current. At first I suspected one of the caps on the 5v standby was too leaky for it to charge enough but, nope, it was the chip itself.

Once it actually gets up to standby power, the set should work fine.

drussel, when you say to ground the external source on the PSU output
connector, which do you mean? I just attached the external GND to the
GND-test point on the PSU. (Please see attached image below)

All I get is three flashes, over and over

Thanks,

Nicholas

[tom66]

Re: panasonic tx-p50x50b

The stby supply also supplies unregulated output Vcc to the PFC and main converter. No Vcc, and you'll get an error code.

[piccy]

Re: panasonic tx-p50x50b

where can i measure that , is it marked vcc on psu board
does anyone have a circuit for this tv ?

[Nicholas]

Re: panasonic tx-p50x50b

In my picture above I have cut the jumper so the +5V standby only goes out, not
back in. Is that wrong?

Thanks!

[Neelix]

Re: panasonic tx-p50x50b

where can i measure that , is it marked vcc on psu board
does anyone have a circuit for this tv ?

In your other post you mentioned that B159-201 is printed on the board. Attach is circuit diagram for the B159-201 board

[tom66]

Re: panasonic tx-p50x50b

Vcc is not marked, but will come off the standby transformer. Also, the 15V is probably generated by the standby transformer too.

[drussell]

Re: panasonic tx-p50x50b

As tom66 pointed out, more than just the 5VSB comes off the standby power transformer so my thought about being able to supply 5v externally simply isn't going to work. (Thanks for posting the schematic, I don't have that set here anymore to refer to, it's back in use.)

Even though it's always nice to have a situation where you can confirm first, I would just try replacing the 6755 controller IC if you have no standby, that will quite likely fix it.

[piccy]

Re: panasonic tx-p50x50b

has anyone got a service manual for this set

[piccy]

Re: panasonic tx-p50x50b

Update on issues with 7 blinks , having found a panasonic guide for another plasma model i did some checks and found by disconnecting S20 connector the light on front flashes green , then goes solid green , short while after i hear what i presume is a relay click and the light blinks red 7 times , i presume in response to the fact i have S20 disconnected

If i take the power feed to the bottom board as well the light remains green

Is this indicating the panel is faulty or does the fault lie solely on the ysus board where the s20 connector is ?

I cannot find any obvious shorts when testing igbt's with meter and peak dca tester the only odd reading i get is when measuring the power diodes where it appears to be dead short across the two anode pins , are they connected together to cope with power ? cant find any datasheets on them or the igbt's

[piccy]

Re: panasonic tx-p50x50b

If i take the power feed to the bottom board as well the light remains green

meant to say

If i take the power feed OFF the bottom board as well the light remains green

[tw2005]

Re: panasonic tx-p50x50b

Update on issues with 7 blinks , having found a panasonic guide for another plasma model i did some checks and found by disconnecting S20 connector the light on front flashes green , then goes solid green , short while after i hear what i presume is a relay click and the light blinks red 7 times , i presume in response to the fact i have S20 disconnected

If i take the power feed to the bottom board as well the light remains green

Is this indicating the panel is faulty or does the fault lie solely on the ysus board where the s20 connector is ?

I cannot find any obvious shorts when testing igbt's with meter and peak dca tester the only odd reading i get is when measuring the power diodes where it appears to be dead short across the two anode pins , are they connected together to cope with power ? cant find any datasheets on them or the igbt's

A separate thread would have been nice to start.

The board should have connectors marked SN2, SN20 and this board is known as the SN board in panasonic speak. It's a combined SC,SD,SU board all in one.

So equivalent to a ysus+upper/lower buffer boards.

Anode-Anode will show short.

If none of the heatsinked components are showing short, have you checked also those large SMD diodes DAF30A? center pin to both outer for short.

If still nothing found on that board next to the SN22 panel ribbon connector there is a test pad VFG & VFO. Check resistance between those and vfg - vf5v

Other testpoints of interest on that board are.

TPVAD

TPSN1

TP VFG
SRV VFO
SRV VF5V

SRV Vsus
SRV P5V
SRV P15V