Panasonic TH-P50V20A no screen

[bradm]

I picked up this tv for $50 not working.
When the power button is pressed the led blinks green then i get 7 blinking red.
I have the service manual and it says check the sc/su boards.
Does that mean i need a replacement? Or can i replace some components? (caps)
I have done plenty of soldering etc so thats not an issue.
I have some pics of the boards.














Thank you for you help

[selldoor]

Re: Panasonic TH-P50V20A no screen

Please can you repost the pictures using manage attachments - jpgs up to 3mb are good
off site in line take a while to load and when they disappear the thread will have no meaning or be of help in the future
You can then eit out the ones you have posted

[bradm]

Re: Panasonic TH-P50V20A no screen

ok will do just need to resize them they are just over 4.77mb
any quick and easy programs for this?

[selldoor]

Re: Panasonic TH-P50V20A no screen

Picresize perhaps - i just use Paint or mircrosoft pic manager which is an Office Tool.

[tw2005]

Re: Panasonic TH-P50V20A no screen

It's a Panasonic, likelihood of badcaps is much lower than say majority of other brands as the brands inside there are nichicon or rubycon.

Any way this series has a common fault of SC boards but since this is 7 blink you may be lucky that it's just the SD/SU boards.

Here's the test to be sure. Disconnect the 3 white connectors on the buffer boards, they're tight but be gentle you don't want to break them.

then remove the 4 gnd screws that mount those boards.

Then on the SC board there is a small 2 pin white connector near bottom left SC50. Those pins need to be jumpered together.

Then turn the TV on, if it goes green LED no SOS blinks then the SC has passed and you need to then test the buffers.

Other wise it's a bad SC and you still need to test the buffers.

[tw2005]

Re: Panasonic TH-P50V20A no screen

Do everyone a favour and resize those pics to 2000x2000 max size and go advanced, manage attachments and upload those pics that way although it's probably too late for you to edit now but if not get rid of them as it's a pain in the ass.

Maybe a moderator can remove them?

[bradm]

Re: Panasonic TH-P50V20A no screen

Do everyone a favour and resize those pics to 2000x2000 max size and go advanced, manage attachments and upload those pics that way although it's probably too late for you to edit now but if not get rid of them as it's a pain in the ass.

Maybe a moderator can remove them?

Ive contacted a mod to do that. nothing yet...
my bad...

[bradm]

Re: Panasonic TH-P50V20A no screen

It's a Panasonic, likelihood of badcaps is much lower than say majority of other brands as the brands inside there are nichicon or rubycon.

Any way this series has a common fault of SC boards but since this is 7 blink you may be lucky that it's just the SD/SU boards.

Here's the test to be sure. Disconnect the 3 white connectors on the buffer boards, they're tight but be gentle you don't want to break them.

then remove the 4 gnd screws that mount those boards.

Then on the SC board there is a small 2 pin white connector near bottom left SC50. Those pins need to be jumpered together.

Then turn the TV on, if it goes green LED no SOS blinks then the SC has passed and you need to then test the buffers.

Other wise it's a bad SC and you still need to test the buffers.

ok removed 3 white connectors, ground screws and jumpered sc50.
still have the flashing green then the 7 red blinks.

[tw2005]

Re: Panasonic TH-P50V20A no screen

Ok, so look like bad SC. Normally they fail with the SC2 pins going short cct.

Here's a guide you can use for this generation. In there you'll find a buffer board resistance test. As a quick check set the meter in continuity or diode test with buzzer/beep and put one probe on one of those gnd plates the bolts go through and then slide the other slowly across all the output connectors where the ribbons go.

you don't want to see anything shorted there, also in the table for resistance check for shorts and then also set meter to appropriate resistance range to check those values.

post all results and measurements.

on the SC check sc2 resistance and all the transistors and see if dead short across any 2 of the 3 pins. Q661 is a common one that shorts and transistors part numbers, DG502,DG402, 30F125 also commonly short.

post results.

[bradm]

Re: Panasonic TH-P50V20A no screen

ok so ive got the sc card out on the bench now.

the sc2 pins are the power coming in? one short one fine, + and -

ok not sure if this is correct but getting shorts on
q662, q621, q642, q641 all 3 pins
D482, Q452 all 3
D401, D402 short on 2
D462, D422 short on 2
Q661 all 3

im seeing quite a few shorts where the ribon cable goes (sc20)

[tw2005]

Re: Panasonic TH-P50V20A no screen

ok so ive got the sc card out on the bench now.

the sc2 pins are the power coming in? one short one fine, + and -

ok not sure if this is correct but getting shorts on
q662, q621, q642, q641 all 3 pins
D482, Q452 all 3
D401, D402 short on 2
D462, D422 short on 2
Q661 all 3

Ok, so you're using gnd and then testing pins. Not quite what I wanted but there's a couple of obvious ones there

Q661 all 3, D482, Q452 all 3

These will be ok, diodes with 2 legs being the same ref point
D401, D402 short on 2
D462, D422 short on 2

This info is confusing, some of these don't exist so I think you have the location numbers wrong.

q662, q621, q642, q641 all 3 pins

SC2 i just wanted the probes put across them but sounds like not showing short which is why you got 7 blink. When this shorts causes PSU short and 4 blink, can be 10 blink.

At least that's a definite yes for SC board failure.

see if you can follow that guide for SD/SU resistance, should be able to do it with them installed.

[bradm]

Re: Panasonic TH-P50V20A no screen

yep my bad..
Q622
Q621, next to q622 ?
D642
D641
all on the same heatsink as D422

ok, just trying to get my head around the resistance test reading again...

[tw2005]

Re: Panasonic TH-P50V20A no screen

example of some of the parts.

[bradm]

Re: Panasonic TH-P50V20A no screen

SC41 2 914k
4 221k
8 no reading

SC42 1 1051k
2 221k
6 no reading

the ones with no reading would give a resistance then nothing...

[bradm]

Re: Panasonic TH-P50V20A no screen

example of some of the parts.

there are some pretty small components there!
would any of them need to be replaced?

[tw2005]

Re: Panasonic TH-P50V20A no screen

Was that tiny ribbon that connects the 2 boards disconnected?

Given your meter is not really good enough I'm going to say most likely they're ok.

first reading they say 2.2m but from memory I got 1.9m.

221k is good and the last is higher than your meter can handle so high resistance, no short which is good.

Usually you'll find shorts there if bad. i have to duck out for a bit but SC should get this going providing the panel is not cracked which only you can tell.

[tw2005]

Re: Panasonic TH-P50V20A no screen

there are some pretty small components there!
would any of them need to be replaced?

yeah, what do you reckon. there's a reason i'm showing you these,

[bradm]

Re: Panasonic TH-P50V20A no screen

yep the ribon was disconnected.

no cracks that i can see...

[bradm]

Re: Panasonic TH-P50V20A no screen

yeah, what do you reckon. there's a reason i'm showing you these,

hehe uh oh, the c541 for example.
is that soldered on top of the board or is it plug unplug?

[bradm]

Re: Panasonic TH-P50V20A no screen

they are soldered. ive done quite a bit of soldering but nothing that small. would need a tiny tip and a steady hand