panasonic th-42px60u power problem no light

[gmzombie]

so im trying to fix this plasma and i have found that there is an open diode at d411 and it is a ST02D-170 which to much surprise i cannot locate on mouser or digikey. is there any place else i can look for this diode. i checked the fuses and they are all good, checked the resistor at r410 and that is good even checked the resistors around it to make sure and no luck. just this one diode..Also on a side note do you think i can take a tuner board from the same class and year but better model th42px600u and put it in my 60u without having an issue. the reason i would like that board is that it has a cable card slot.

[PlainBill]

Re: panasonic th-42px60u power problem no light

Datasheet for the ST02D-170. It will read open on any normal DMM.

PlainBill

[Toasty]

Re: panasonic th-42px60u power problem no light

Check R413 also. Same as R410. Fusible 10Ω, 5w.

Any voltages at all?

[gmzombie]

Re: panasonic th-42px60u power problem no light

crap i thought i found the problem..well back to the drawing board. yea i checked both of those fuses and they check out good. there is no power to the system at all. i checked main power coming into the board after the inline filter and there is power there.

[PlainBill]

Re: panasonic th-42px60u power problem no light

crap i thought i found the problem..well back to the drawing board. yea i checked both of those fuses and they check out good. there is no power to the system at all. i checked main power coming into the board after the inline filter and there is power there.

Do you have standby power? If not, check the standby section of the power supply. As has been mentioned many times, pictures help. Attach using 'Manage Attachments' (below the text entry area).

PlainBill

[Toasty]

Re: panasonic th-42px60u power problem no light

Fuse PR401 good?

Do you have power across C407 22uF/450v ?

[gmzombie]

Re: panasonic th-42px60u power problem no light

no standby light or anything. power at c407 of 66volts. all 3 fuses good. although the pr601 on the cold side of the board doesent get any voltage like the other fuses

[Toasty]

Re: panasonic th-42px60u power problem no light

Check AC ~ voltage across R483 - 4.7MΩ

Check AC & DC voltages at bridge rectifier D404. If both are line voltage, then disconnect power, discharge C407 and do a diode check on D435.

I think 1/2 of D404 is open, hence the 1/2 line voltage at C407.

[gmzombie]

Re: panasonic th-42px60u power problem no light

ok first off i must apologize i must have checked the wrong cap when you had me check the c407 before because now i have a voltage over the c407 of 157v dc.
now i checked d404 and voltages were as follows ac was 58/54 and dc was 66/60. R483 has 115volts ac on it when plugged in. diode check on d435 comes out at a .471 rating.again i must have checked the wrong cap or had the wrong setting on my multimeter.

[Toasty]

Re: panasonic th-42px60u power problem no light

I don't understand how/why you are getting/giving 2 voltages unless you are measuring from a wrong point. Across the bridge input you should have ~120VAC and on the output ~160VDC.

Regardless, the voltage across the cap is good, so this was a false lead.

Check across the other bridge rectifier, D401 the same way.
DMM probes to the 2 ~ ~ marks for AC voltage and black to - and red to + for DC

Any clicks from the relays when you plug it in?
Leave it unplugged for 30 secs or so then listen when you plug it in.

EDIT:
>>all 3 fuses good.<<

There are 4... perhaps 5 ?
2 cartridge style and 2 can style that are reddish brown.

2 cartridge and 1 can in lower right, 1 can in upper left in between the big caps.

On the backside pics, there is one indicated on the first backside (full) shot to the left of the horizontal slot. The fuse marking shows it horizontal but the wording runs vertical above it --> LF F5AH 250V


Can't see anything under those heatsinks so some side shots would help.
.

[Toasty]

Re: panasonic th-42px60u power problem no light

See if you can locate TP1 or TP2 and see if there is DC voltage present.

[gmzombie]

Re: panasonic th-42px60u power problem no light

ok because im an idiot on the d404 i was checking the volts the wrong way..sorry ive been on call all week and my brain is now fried. Anyways ac volts on d404 is 115 and dc volts is 114 tested properly now. d401 has no volts on ac or dc. i went ahead and tested voltage on c470 which is the first big blue cap? that power would go through to get to the d401 and there was nothing. i then rechecked r483 and there is 115v ac on it like before. tp1 and tp2 have a dc volt of .217. i also went to check the ac volts coming into that d401 and there is none. and to follow up on a previous question there is no voltage at r410 there is however volts ac at r413 which is why we get power to the d404. hopefully this helps and i hope i saved a few steps. and as always thanks for the help.

[Toasty]

Re: panasonic th-42px60u power problem no light

Indications are the standby supply is dead or has a problem.

From the COLD side negative/ground, measure the voltages at the cathodes (striped end) of D509 (5VSB) and D511 (12V). Both are just above T410. Hint: Pins 10 & 11 on T410 are tied together and are ground.

Again:
- Did you check the other fuses? (Total of 5?)

- Any clicks from the relays when you plug it in?

Please hit enter once in a while instead of one big paragraph.
Very difficult to read and understand.

Main and Power Board Block diagram PDF's attached.

.

[gmzombie]

Re: panasonic th-42px60u power problem no light

ok first no clicks or anything when turned on. did what you said and nothing

second getting 5vdc on cathode side of d509 and 13.7vdc on d511

yes i meant 5 fuses good. 3 tubes and 2 red/brown cap like ones. all test good.

[Toasty]

Re: panasonic th-42px60u power problem no light

With no clicks, no lights, good fusible resistors, and good fuses, I'm suspicious of the Power MCU, IC501.

Check all the (white) ceramic power resistors, and the blue 2w resistors with the printed values too. Such as those in your pics #3 & 5 in Post 12.

Just so you are aware, the board needs to be -completely- installed when checking voltages from here out, with all connectors and screws to the chassis in place. Reason is, it sends standby voltage to the other boards to see if they are okay before it brings up the main power.

Was there anything that happened to the TV that may be a clue? Lightning storm, power surge, were you watching it when it happened?

What is the TNP number on this board? TNPA3912?

.

[gmzombie]

Re: panasonic th-42px60u power problem no light

ok checked those power resistors and with ac volts i get about .417 no dc volts on the white ones
i cant quite get under that top peice with my leads to check that other 2w on tha back side of it but one side says .410 volts ac.

i believe the guy i got the tv from said there was a power surge i think and after that it stopped working.

TNPA3911

[Toasty]

Re: panasonic th-42px60u power problem no light

No, no...

When I say to check a resistor, I want you to use the resistance scale and compare it to the markings on the resistor. I want to see if any of them are open.

Make -sure- the set is unplugged and there are -zero- volts across them before you begin checking them. Then switch the meter to the resistance scale

In the top-down shots in Post 7, the pics 1 & 4 show one of the blue ones about 2 inches to the right of the big caps. You can see a marking of 0.22Ω, so set the meter to the lowest resistance scale and see if the reading matches or is even less than what that is marked. Do this to all the others I spoke of before.

Report any that are open... i.e.- the same as not touching the leads together.

EDIT:
You should be able to get to the leads of all these resistors without probing from the back.
You can have the board out of the set, if necessary, to check the resistors.
.

[gmzombie]

Re: panasonic th-42px60u power problem no light

ok so all 3 of the resistors the 2 white ones and the blue one all have readings of .2ohms.

[Toasty]

Re: panasonic th-42px60u power problem no light

That matches what is printed on them, correct? There are at least 2 blue ones as I said, Pics 3 & 5 , Post 12.

My diagnosis, without having the unit to hand:
Because there are no blinks or indications from the LED, I believe the power controller MCU, IC501, is toast. That chip drives the LED when there is a power supply problem. (4 blinks) The LED also can't blink for any other problems because the chip is not allowing the other standby voltages to come on.

If you watch eBay, you can probably get a used TNPA3911 (no suffix) one from a working set for ~$70. One was up for Buy It Now until this morning for that money. Make sure you get one that has a non-DOA guarantee or at least 10 days to return it.

There are a few vendors on the net that have this for ~$120+. Most will offer a 30 day to 6 month warranty.

Where are you, by the way?
Be too funny if you were right down the street from me.

Toast

PS: Schematic of P Board attached. Hopefully someone else will chime in here.

.

[gmzombie]

Re: panasonic th-42px60u power problem no light

wyoming, mi is where i live. couldnt i just get the ic501 chip and replace it or is this a special chip or do you think there is more wrong on the system.