Panasonic TX-L55WT50B

[comptek]

Hi guys hope you are all well
Hoping there are some Panasonic specialists about I have the above model
Tx-l55wt50b I have looked for a schematic of the power supply and couldn’t find one even the service manuals only cover everything else but the psu.
Anyway I got the tv and it was making a loud buzzing noise from the back opened it up and found that IC571 / 2A fuse / a couple of zeners on the back had blown

Power supply CT31004 U84PA-E0011754B

Replaced IC571
Replaced fuse with a temp 2A wire
I had zeners in place but probably wrong as when I plugged it in all that happens is the red light flashes 3 times pause 3 times pause and so on.....

Position ZD571 was a G5 zener I think I found an equivalent?
Position ZD572 Empty had a zener there that was short
Position ZD552 Found to be shorted too

Can anyone point me in the right direction of the values/ Equivalent or a manual for the power supply

Thanks in advance

Gary

[comptek]

Re: Panasonic TX-L55WT50B

Here are some photos

[R_J]

Re: Panasonic TX-L55WT50B

A 3 blink sos refers to an "A" board fault, Was there a number on IC571?

[comptek]

Re: Panasonic TX-L55WT50B

Hi RJ, there was a number that I had to clean off the black glue to find and piece together it was FSFR1700XSL I purchased two just in case...
I need to get the power supply back to standard before I can test anything else
When I got the 3 flashes i set out to find some zener diodes, it was then when I took the diode off of the lower side to test it that I found it it was short so that may have caused the 3 flash sos

[comptek]

Re: Panasonic TX-L55WT50B

Hi guys any other help available
Schematic diagram of power supply?
Approx values of zeners ?

Thanks in advance
Gary

[Diah]

Re: Panasonic TX-L55WT50B

f you upload a complete photo of yours PSU from both side. and remark the area you have short on it will be more essential, because from my know early Panasonic TV PSU used same main diagram to build any further versions. so any early Panasonic psu boards will give the answer on any missing mysteriously parts.

[R_J]

Re: Panasonic TX-L55WT50B

I'm not sure if this will help, but this Samsung power supply uses the same ic. The BN44-00498A uses it as well.
The ZD572 seems to be between Lvcc and ground, so I suspect it is just for over voltage protection. IC lvcc max is 25v so it could be a 18~20v zener
ZD573 is on the CS, current sense line to ground, this pin sees a very low negative voltage so I would guess a zener of around 4.7v or maybe less?

[comptek]

Re: Panasonic TX-L55WT50B

Hi guys I fixed it
I replaced the faulty zener diodes with what work out to be 4.5v ish and it's working now all there was 3.2volt and 5 volt that was all
Now all voltages are up
Crikey wow what a picture on it I'm going to run it for a couple of days

[R_J]

Re: Panasonic TX-L55WT50B

Are you sure you used a 4.5v zener for ZD572 & ZD552? That is the Lvcc line and should be around 12 volts
I can see 4.5v for ZD573 & ZD553 but not ZD572 or ZD552

[comptek]

Re: Panasonic TX-L55WT50B

Are you sure you used a 4.5v zener for ZD572 & ZD552? That is the Lvcc line and should be around 12 volts
I can see 4.5v for ZD573 & ZD553 but not ZD572 or ZD552

I will double check R J but it's been on all day I keep switching it off and back on and it seems fine at the moment

Regards
Gary