Panasonic TH-P42A2G SN Board Problem 4 blinks

[heri]

Dear forum,

I have pan 42" plasma which can't start and display 4 blink on power red led.

I've seen other thread this caused by SN board..so i unplug it..then TV can start on with green power led and can response to remote control.

Please help where should i start searching failure..??

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

i have circuit same as tc-p42c2

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

checking voltages:
vsus in power supply is 423v
vmid in ss board 62v

is this okay..??

[tw2005]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

Can you confirm which board you have disconnected or how?

The TNPA5066 SN board on the left or the TNPA5072 SS board on the right?

It seems unusual that you can disconnect the SN without the TV shutting down with an error blink.

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

i disconnect tnpa 5066 -> power (sn3,sn2) & ribbon cable (sn20).
tv no error & response to remote control.

[tw2005]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

checking voltages:
vsus in power supply is 423v
vmid in ss board 62v

is this okay..??

try using DC range. you have it set on AC. Vsus would typically be 195 -205V DC across P2 or P11.

A 4 blink suggests a dead short on the Vsus line so i would check across the 2 pins at SC2 and see if short or low ohms. Also check acros SS11 for dead short on the Vsus - gnd.

have the TV off and be aware that the volatges can remain at p2,p11,p35 for some time so reconnecting to boards can arc and damage things

Common fail on these is the SS board going dead short and you'd find the RJP30E4 IGBTs shorted out, but the SN could have failed short too.

On the SN check Q661 for dead short or RJP43F4 or RJP56F4 transistors for dead short.

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

using dc measure:
vsus 191v
vmid 32v

I forgot to check ohm for SC2 pin, I've been took off diodes i suspect short D401, D641, D722, & D724 that not short.
(sc2 is open / no short, i'll check again after resolder these diodes)

Is those IGBTs should take off from board to check..?

I think SS board is okay since i can turn off using remote.

[Moreno83]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

The mainboard controls the on/off not the SS board.

You don't need to take the IGBT's off the board to test them for short. Just use multimeter in diode mode and put the propes on the outer pins. If you hear a beep then they are short.

[Moreno83]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

What chassis is this? It's best to have the service manual and schematics.

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

where to find chassis code..?

[tw2005]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

where to find chassis code..?

It does not matter. You have a 2010 HD TV with TNPA5066, TNPA5072 boards and as you say is pretty similar to the 42C2 or even the 42X20A since we have a green and red LED and the US only have red.

If the TV has a 4 blink and then you isolated the SN and the 4 blink goes away I'd think the SN was the issue. Something has to be shorted on that and it's most likely going to be the transistors at least. The diodes are A-K-A so you check A-k not A-A. (Anode, K cathode)

I have no answer for it staying on, SN20 disconnected should trigger 6 blinks.

What resistance do you measure across the SN2 pins?

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

found Q402 & Q661 dead short.

it should be caused by other circuit block near..isn't it..?

@tw2005 resistance of sn2 is about 2000 ohm then seconds later its open circuit.. i think its caused by cap 412 (250v/1.5uF).

[Alastair E]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

Q661 short--Check replace Q702, Q701, D702, IC773, IC771, PC461.--Best to change this lot on sight.

Q402 short CHANGE IC501 and Q501. Check ALL IGBT's on heatsinks, prob find more short or leaky. Check All Buffer-chips for issues to VFG....

--These boards can be a nightmare--IF you don't get all the faulty parts the first time--It'll all blow up again--Instantly!

Best to remove the plugs and solder ALL the thick cables between the SN and the SS as well as the PSU. A slight dodgy plug/socket on ANY of those leads can instantly kill the SN again--I know this because it happened to me. I now cut all the plugs off and solder the cables to the boards...

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

Alastair..can you please inform the diode D701 D702 Q702 and Q501 part or datasheet ..? Thx b4.

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

measured Q701 & Q702 is short (inverter block), then I replace with MMBT3904 & MMBT3906..
trial turn on power..board short again, these transistor short again..
what causing these Q701 & Q702 short..?

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

note that all IGBTs are okay, since I've purchased new IGBT items from utsource.net

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

Where can I buy a TNPA 5066 SN Board for my plasma tv..?
Since I'm desperate repairing this bad board..:/

[heri]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

IC461 (PS9856) measured about 50 ohms pin 8 to ground, but open circuit if removed from board.
Is this normal or this IC broken..?

(symptom now change 6 blinks)

[tw2005]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

So on the board location for this opto, what's the resisitance between pin 5 & 8? Is it the same 50ohms?

What is everything you have replaced so far.

[tw2005]

Re: Panasonic TH-P42A2G SN Board Problem 4 blinks

Hope you realise the original Q701 & 702 are 2PD601ART and MMBTA92 respectively.

That would mean your MMBT3904 is about 20V underspec and your MMBT3906(40V 0.2A, PNP) is about 260 volts under rated as the MMBTA92 is a 300V 0.5A PNP