Panasonic TH-50XP70BA

[24mech]

Good morning I'm hoping someone on here will be able to help me out with a schematic for the power supply (EXTMM655MEH) of my 50" Panasonic TH-50PX70BA I've been using the schematic attached below though I don't think its quite right.

Here is the issue I'm having:-

TV: Panasonic TH50-XP70BA
Fault: Not powering up red flash code 12

Voltage for sound abnormality Sound SOS

I've checked for 15v on the connectors to the A board from the P board but it appears to be missing so I'm looking for a schematic to enable me to find the faulty component on the P board. Thanks

[tw2005]

Re: Panasonic TH-50XP70BA

https://www.badcaps.net/forum/showthread.php?t=34491

post 10 has a link, PSU fixed that one, worked out 15v was available, just not being switched on by MC351, no signal from PSU micom MC701 to turn on MC301 reported by OP.

Edit: Not sure if you can edit the model to "PX", helps for when someone uses the search feature using the model number

[24mech]

Re: Panasonic TH-50XP70BA

I did a search (that post didn't show up in my search) sorry if I have offended you by not finding the post you have linked to. Ive been all over elektrotanya looking for a SM for this unit but there isn't one listed the one linked to in the post is for PANASONIC TH-50PV70F P 50PX70B E CH GPH10DE SM which is why I was using the schematic I have attached. I said in my 1st post that there is no 15v coming out of the P board to the A board and I'd like to repair the board rather than replace it I have checked the circuit from pins 2,3,4 of P6 and 1,2 of P7 back to MC351 but with this not being the correct schematic I was hoping to get my hands on the correct one before I went any further, are you telling me that this schematic is ok for diagnosis? thanks for you help with this issue :-)

[tw2005]

Re: Panasonic TH-50XP70BA

OK. So this model is not the same as 70B and has an A board? Try downloading TH-50PX75U manual, has the PSU model you mentioned but at a glance it's looking real close.

If you can upload some pictures of the layout of this model.

[24mech]

Re: Panasonic TH-50XP70BA

So what your saying is I should be seeing 15v coming from pin 15 of the MC701 to pin 4 of the MC351 when the unit is powered up and if that is not present then the fault lies with MC701 not switching on MC351 is that correct?

[tw2005]

Re: Panasonic TH-50XP70BA

So what your saying is I should be seeing 15v coming from pin 15 of the MC701 to pin 4 of the MC351 when the unit is powered up and if that is not present then the fault lies with MC701 not switching on MC351 is that correct?

No,not sure of the level but I'd expect a few volts, have a read through that other post. To be honest not 100% sure but from what PaulF was reporting he had 15V on one side of Q351 which is switched on by the module MC351 after MC701 turns it on.

We could be wrong about how the cct works exactly. We do know it was the PSU and maybe this is a similar problem to the PZ80 PSU with those modules having bad ceramic caps.

Not sure if heating those or freeze spray and see if it gets a change.

[24mech]

Re: Panasonic TH-50XP70BA

I'm confident the fault lies with the PSU and am happy to replace the board as a unit, I just like to know how and why these things fail (to prevent repeat repairs) and I'm always looking top improve my knowledge :-) I'll put the unit back together this week and carry out some more voltage checks on the terms 15 and 4 to see whats going on, I'll post back once I have something more to report. Thank you.

[tw2005]

Re: Panasonic TH-50XP70BA

I'm confident the fault lies with the PSU and am happy to replace the board as a unit, I just like to know how and why these things fail (to prevent repeat repairs) and I'm always looking top improve my knowledge :-) I'll put the unit back together this week and carry out some more voltage checks on the terms 15 and 4 to see whats going on, I'll post back once I have something more to report. Thank you.

I'm sure if you work it out you'd be helping a few people out. Had a quick look for a component fix in a few posts, empty handed.

At least you get decent diagrams with the panasonics.

[tw2005]

Re: Panasonic TH-50XP70BA

This post https://www.badcaps.net/forum/showth...ighlight=mc351 may be a little unrelated but in there mentioned MC301,MC351 and some othe bits. MC301 is the common one with a bad ceramic.

It's the 42" version of yours but the PSU must be similar design as yours if they're mentioning those modules.

[24mech]

Re: Panasonic TH-50XP70BA

Hi everyone I have some more info so, I have traced the voltage circuit and this is what I've found. from T301 (I assume this is the voltage transformer) on JD6 and JD7 I see 0.9v at power on, this 0.9v can be seen at MC351 on pin 7 and at MC701 at pin 1 (I assume this is the self check for the 15v circuit) also at pins 2,3,&4 of connector P6 and 1&2 of connector P7 so from this I'm thinking that the cold side of the circuit is all ok and the fault lies with the conversion of the voltage to 15v

lmao ho hum..... maybe I should read other peoples post before I start to write lol thanks for the info tw2005 so its worth me replacing the 1.0uF resistor on the MC301 and MC201 then? I'll order some now :-) thanks, I'll keep you all posted.

[vinceroger69]

Re: Panasonic TH-50XP70BA

quote!! lmao ho hum..... maybe I should read other peoples post before I start to write lol thanks for the info tw2005 so its worth me replacing the 1.0uF resistor on the MC301 and MC201 then? I'll order some now :-) thanks, I'll keep you all posted.

make sure you order 1uf 50volt panasonics i just used ordanary leaded ones and glued the capacior to the ic mines been working great a verry fiddly job look at the video for tips and remember to mark which ones is mc301 and m201 as they might be different took me about 2 hours to do the whole job as was fiddly and loads of screws lol.

[24mech]

Re: Panasonic TH-50XP70BA

the tv's apart and I've had the power board off its ally cooler before,as for the caps I just ordered two Radioshack 1.0uF 35V 20% Dipped Tantalum Capacitors, will they be ok? also are these going to be polarity conscious if so which way do they need to be fitted thanks here are some pics :-)

[24mech]

Re: Panasonic TH-50XP70BA

Hi all I have now replaced the capacitors on the boards MC301 and MC201 but I've still got no 15v, I see on the other post link he's talking about bad/poor wiring plug connections. can this cause no power on the 15v ? or does anyone have any other suggestions thanks.

[24mech]

Re: Panasonic TH-50XP70BA

Hi once again all, I'm getting no ware with this TV... so back to the start then.
I've gone back to the flow chart and have a question I've done the remove A5, A6 and A7 and no the TV did not turn on with a white screen, so I reconnected the connectors A5, A6 and A7 and disconnected SC2 and SC20, Now here's the question the power light comes on green and then starts to flash code 12 so does that count as the light staying on or not? if it counts as staying on then the flow chart points to the SC board? any body got any ideas?

[tw2005]

Re: Panasonic TH-50XP70BA

Hi once again all, I'm getting no ware with this TV... so back to the start then.
I've gone back to the flow chart and have a question I've done the remove A5, A6 and A7 and no the TV did not turn on with a white screen, so I reconnected the connectors A5, A6 and A7 and disconnected SC2 and SC20, Now here's the question the power light comes on green and then starts to flash code 12 so does that count as the light staying on or not? if it counts as staying on then the flow chart points to the SC board? any body got any ideas?

no, what they're after is a solid lit, normal startup. Blinking is error.

have you checked out Q351,MC351. with PaulG's 70B which does not have an A board he found 15V was generated but not switched on for the sound by Mc351/Q351.

Does this have a D board? I'm unfamiliar with these but i'd continue down the flow chart and see how you go.

[tw2005]

Re: Panasonic TH-50XP70BA

Any chance you can get a clear shot of MC351 module to see the cct and components.?

[24mech]

Re: Panasonic TH-50XP70BA

Thanks for your help tw2005 I've continued with the flow chart, its telling me to remove the jumper from SS34 and install it across pins 8 and 10 of P12 so I have removed the power switch and installed it across pins 8 and 10, still getting the flashing error, Next step: Do pins 1 and 2 of CN P25 output 15V before the unit shuts down, No I get a spike of 0.8v if the units been of for a long period if time and a steady 0.1v if its off for a few minutes so the flow chart is pointing to the P board. I'll take a picture of the MC351 when I get back I'm just heading out right now thanks

[tw2005]

Re: Panasonic TH-50XP70BA

I'm expecting the same fault , that being the PSU. Sorry if the MC201/MC301 threw you off the scent. The main reason I dug up the post was there was a reply in there from a pana service agent and mentioned was MC351 as part of a trio of modules to be replaced.

Seems to indicate to me MC351 may be a known issue and was hoping it may be something really simple like a cap etc on that board.

That module turns on 2 separate 15V lines Q351 & Q352 both come from the same source.

Just need to deduce how MC351 switches Q351 on.

[tw2005]

Re: Panasonic TH-50XP70BA

Thanks for your help tw2005 I've continued with the flow chart, its telling me to remove the jumper from SS34 and install it across pins 8 and 10 of P12 so I have removed the power switch and installed it across pins 8 and 10, still getting the flashing error, Next step: Do pins 1 and 2 of CN P25 output 15V before the unit shuts down, No I get a spike of 0.8v if the units been of for a long period if time and a steady 0.1v if its off for a few minutes so the flow chart is pointing to the P board. I'll take a picture of the MC351 when I get back I'm just heading out right now thanks

Sounds like you're following 10 blink chart not 12? On the PSU, next to MC351 there's a post TP7. If you hook up there and turn on should see 15V.

[24mech]

Re: Panasonic TH-50XP70BA

Hi again tw2005 I'm following the 12 blinks attached, as for TP7 I'm getting 0.1v so does that mean the 15v isn't coming out of the high voltage side then?
if so am I heading back to the MC301, MC201?