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Help fixing TV Panasonic TX-P42UT30E

Cevi

May 27, 2016
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Hi guys. I finally found time to try to repair my sister's Plasma TV which was fried after electricity drop. The TV is totally dead without the standby light turning on.
I got it opened and realized that I don't get those 5V on the standby pin.
I can't find datasheet for the power supply so It's kind of difficult for me to trace back the voltages.
The main fuses are OK since there is high current flowing through the board. I have basic knowledge of electronics so I'll do my best to follow the instructions if any.
- The model of the TV is: Panasonic TX-P42UT30E
- The model of the PSU is: NOAE6KK00008
This is the PSU BTW (Not the actual I got, just for reference)
Thanks.
 

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Cevi

May 27, 2016
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Can we see a picture of the genuine article?

It may be possible to identify a fault from a close up image.
Here is a close up from the actual board. If you can notice above the board is the rectifier diode which I found to be faulty. The model of the diode is RM11C. Since I didn't had the exact model I've used the RL207 which has higher current and slight different peak. Even after this I still don't get those 5V on the stb pin. Since I am new in the TV repair world I guess I can get these 5V with the board detached from the TV right?
WP_20171028_20_13_26_Pro.jpg WP_20171028_20_14_02_Pro.jpg
 

kellys_eye

Jun 25, 2010
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Yeah, without the schematic this isn't going to be easy....

All I can suggest is a methodical approach. Starting at the AC input, the input filter components (where a transient absorber may have popped) then to the main rectification and smoothing.

A mains supply surge 'shouldn't' get past the input stages so we need to identify those parts and test there first.

The components on the right hand side are the 'input' (basically anything OUTSIDE the broad white band that encompasses the SMPS sections). If the standby supply is also generated in an SMPS fashion then it's likely to be via the smallest of the ferrite transformers situated just above the six opto-couplers (little black boxes in a vertical line).

If you can post a high res picture of the right hand side - multiple sections if you have to - this will help identify where measurements are required to be made.
 

Cevi

May 27, 2016
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Yeah, without the schematic this isn't going to be easy....

All I can suggest is a methodical approach. Starting at the AC input, the input filter components (where a transient absorber may have popped) then to the main rectification and smoothing.

A mains supply surge 'shouldn't' get past the input stages so we need to identify those parts and test there first.

The components on the right hand side are the 'input' (basically anything OUTSIDE the broad white band that encompasses the SMPS sections). If the standby supply is also generated in an SMPS fashion then it's likely to be via the smallest of the ferrite transformers situated just above the six opto-couplers (little black boxes in a vertical line).

If you can post a high res picture of the right hand side - multiple sections if you have to - this will help identify where measurements are required to be made.
While I'm taking the pictures from the board could you please check this service manual I just found. It is for the TX-P42UT30B and TX-P42UT30Y model but maybe they have the same PSU
here is the link: https://www.electronica-pt.com/esqu...nasonic-tx-p42ut30b-y-chassis-gpf14d-e-28299/
 

kellys_eye

Jun 25, 2010
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... I need the pics from the 'cold' area!

Anyway.... if the schematic you found is anything to go by, check out the diagram below:

PSU.png

You need to 'chase' the supply continuity from the AC cord input, via the fuses, L101 and filter, up through the bridge rectifier and to L601/602, D607/608 and F201 and Q202/203.

This is the path for the standby supply and, as you surmise, nothing else happens without it.
 

Cevi

May 27, 2016
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Thanks, I've updated the album with photos from the Cold area and you can check them out on the same link I've shared earlier. Since it is a high voltage (220/230V) where should I last get these ratings along the paths, on which points (some diode, transformer, rectifier ...), so I will be able, at start, to discard the Hot area as faulty?
Thanks.
 

Cevi

May 27, 2016
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Ok found this guy fried (RWT05 10RJ). According to his schematic I should get line between his closest pins right?

Fried-Fuse.jpg

Fried-Fuse-Back-Side_LI.jpg
 
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Cevi

May 27, 2016
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Can I use any kind of 5W 2A Ceramic Thermal Fuse or it has to be this exactly? What are the required parameters for this fuse?
In that case I will need to solder jumper from one of the end of the fuse to the second contact on the board. Something like this I guess?

Alternative-Fuse.jpg


EDIT: This will be the right Fuse placement I think:

Alternative-Fuse-03.jpg
 
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kellys_eye

Jun 25, 2010
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It's a 142 degrees C thermal protected resistor. IIRC the 'top' pin is just to assist in physical location on a circuit board and the resistance is measured between the two adjacent pins. If it measures open-circuit you need another one.

The three-pin connection arrangement can be confirmed by checking against the pcb track layout to confirm the 'third pin' isn't forming part of any conductive circuit.

These devices are CRITICAL SAFETY COMPONENTS and need replacing with identical devices to retain the full safety aspect.

They are made by 'Stackpole' and Digikey stock some of their range but I'm not sure which wattage yours falls under (10W I'm guessing). Have a look here:

https://www.digikey.co.uk/products/...B10R0-ND&part=VM3JB10R0-ND&part=VM10JB10R0-ND
 

Cevi

May 27, 2016
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It's a 142 degrees C thermal protected resistor. IIRC the 'top' pin is just to assist in physical location on a circuit board and the resistance is measured between the two adjacent pins. If it measures open-circuit you need another one.

The three-pin connection arrangement can be confirmed by checking against the pcb track layout to confirm the 'third pin' isn't forming part of any conductive circuit.

These devices are CRITICAL SAFETY COMPONENTS and need replacing with identical devices to retain the full safety aspect.

They are made by 'Stackpole' and Digikey stock some of their range but I'm not sure which wattage yours falls under (10W I'm guessing). Have a look here:

https://www.digikey.co.uk/products/compare/en?RI=53_0_0_0_0_0_0_0_0_0_0_0_0_0_|fffc02e2,mu10+Ohms|2085,ffe00035&page=6&part=VM2JB10R0-ND&part=VM5JB10R0-ND&part=VM3JB10R0-ND&part=VM10JB10R0-ND


Yes the third pin is soldered on an empty pad on the board.
Fuse-Replacement-Empty-Pad.jpg
So I guess I should try more harder to find an identical one. I'll do my best and will tell you then.

According to this code reading it looks like is 5W
20150717-35.png


Here is the whole description:
http://www.akaneohm.com/products-data-eng/rwt05a/
 
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kellys_eye

Jun 25, 2010
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Spot on with the tech spec. The two-pin version should be fine unless you're in the habit of bouncing the TV around a lot.... but ideally a like-for-like substitution is always the best option.

Thing is, that resistor was put there to protect things so you have to ask the question, what may have gone wrong to cause the (fused)resistor to blow? and investigate after that position to see what else may have gone wrong.
 

73's de Edd

Aug 21, 2015
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Add on . . . .
On the photos in 9 and 10.
In agreement . . . that the left termination is just being a dead terminal at the board propers foil land and just serving for 3 point mounting stability. . . . . vice a floppy 2.

There IS a 10 ohm resistor inside the unit that is in close /to/ intimate contact with a thermal fuse link that opens up at approx that sustained temperature specification .

So you may have drawn in your resistor or fuse link positions being transposed but you should be able to read both .
One path as being a near short for the link, or the other as the specified 10 ohms, or read be able to read 10 ohms thru the series pair for a good unit.
My suspicion is only for the link to be open, with the 10 ohms still intact or you may have a DEAD shorted bridge or semi on past it that is dead shorted and overloaded it SOOOOO hard that the 10Ω went also .

I don't think that the CORRECT schematic snippet is being used for THIS specific set.
But this part would equate to R104 on the supplied schematic snippet.

You can see that this part is being across a power relays switching contacts, located just above it, and relates to being used for surge absorption before FULL power application is accomplished with that power relay contacts closure. (That it is shunted across.)

Addenda . . . poked this up earlier but g-g-daughter on 'puter . . . only able to add at this moment.
You got the exact info on the unit now , but it should not be the factor that is killing the set.



73's de Edd
 
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Cevi

May 27, 2016
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Spot on with the tech spec. The two-pin version should be fine unless you're in the habit of bouncing the TV around a lot.... but ideally a like-for-like substitution is always the best option.

Thing is, that resistor was put there to protect things so you have to ask the question, what may have gone wrong to cause the (fused)resistor to blow? and investigate after that position to see what else may have gone wrong.
As far as I know the TV was in standby mode when suddenly an electricity drop occurred and in short interval it came back. I guess during the comeback there was an higher amperage wave that struck the TV so the first component (as for now) that didn't survived this was the rectifier diode D309 (RM11c). When I take it away and measured it (in diode mode) it was allowing flow in both directions showing 0.02 (whatever unit). Next, this diode is connected to D305, D306 which as I can see have dark shade on the pads but are still functional. After this (I guess) the thermal resistor got blown away.
Here is a picture from the D309 rectifier diode which currently and temporary I've got it replaced with RL207:
RM11c.jpgRM11c-Back.jpg
 
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Cevi

May 27, 2016
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Add on . . . .
On the photos in 9 and 10.
In agreement . . . that the left termination is just being a dead terminal at the board propers foil land and just serving for 3 point mounting stability. . . . . vice a floppy 2.

There IS a 10 ohm resistor inside the unit that is in close /to/ intimate contact with a thermal fuse link that opens up at approx that sustained temperature specification .

So you may have drawn in your resistor or fuse link positions being transposed but you should be able to read both .
One path as being a near short for the link, or the other as the specified 10 ohms, or read be able to read 10 ohms thru the series pair for a good unit.
My suspicion is only for the link to be open, with the 10 ohms still intact or you may have a DEAD shorted bridge or semi on past it that is dead shorted and overloaded it SOOOOO hard that the 10Ω went also .

I don't think that the CORRECT schematic snippet is being used for THIS specific set.
But this part would equate to R104 on the supplied schematic snippet.

You can see that this part is being across a power relays switching contacts, located just above it, and relates to being used for surge absorption before FULL power application is accomplished with that power relay contacts closure. (That it is shunted across.)

Addenda . . . poked this up earlier but g-g-daughter on 'puter . . . only able to add at this moment.
You got the exact info on the unit now , but it should not be the factor that is killing the set.



73's de Edd
This is what I get fwhile measuring the Thermal Fuse Resistor:
Fried-Fuse-Measurements.jpg
I guess the fuse is fine and the resistor is the blown one and their link inside is still intact. If this is the case (call me crazy but I am an amateur in these :) ) what are the chances that I solder a 10 ohm resistor over the old one from the outside of the body?
 

Cevi

May 27, 2016
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And I still don't get the point with this Thermal Fuse with Resistor. Why the resistor and not just the fuse or why not just one by one first the fuse then the resistor or vise-versa?
Is it because of the box which in case of overload will possibly hold the high generated temperature and by this damage the nearby components?
I really wan't to solder a 10 ohms above the case guys :) Just to check further if something is damaged along.
Please tell me I can. :) I know is against the rules of electronics but I really want to try this. :)

Another crazy idea: :) Can I just make this custom made Thermal Fuse Resistor by my own? :)
Custom-Made.jpg
 
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73's de Edd

Aug 21, 2015
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Sir Cevi . . . . .

OBSERVATIONS . . .

On your photos of post 10, in actuality, both part configurations being drawn in are incorrect.
To amend, you go to the right, to see the two connections and draw in a 5 ohm resistor that is being in series with a thermal fuse link. They connect to that pair of connections.
The far left connection makes no significant connection into actual board circuitry, with it merely serving as a mechanical support tiepoint.

The available manuals given are of no use in providing a complete schematic of the power supply proper . . . its totally not being provided, probably only being available as / from the Sanken sub supplier / module builder.

The parts list referencing is also a royal mess.

Ergo . . . I have marked up a block diagram with the critical power flow paths of our main interest.
That is going to be the AC input and its connectivity into the "400" series standby circuit and its offshoots.

Follow the entry flowpath of the HOT A.C. line at the far left .
Its being recolored up as VISIBLE PURPLE, with flow direction arrows.

It initially comes in and comes down to your now open circuit 10 ohm + thermal fuse R104 and then the power was supposed to flow down to your already found . . .dead shorted . . .D309 half wave diode that is used for providing power for the standby supply circuitry.

The inset pic . . . of a portion of the PCB . . . shows the non disclosed C404 filter capacitor for this supply.
Then you encounter a series F401 fuse, and you may have to look hard for this one, just in case you are expecting a conventional large glass fuse.
Since it very likely might be disguised as a mini PICO brand , wired in fuse in a green / khaki / black case.
If you find it blown open circuit, you will see that the power then would have flowed thru the primary winding of the T401 sby power transformer and ended up connecting into the Z401 switching semiconductor / device.
You need to track that down and give the numbering on it . . to research out.
That could possibly be dead shorted inside to hot ground also.

Confirm that by going to low ohms and metering by having ground probe going to a TRIANGULAR ( HOT ground connection) and the other probe goes to either of the primary wires or over at the right terminal of F401.
Looking for high resistance . . . being good . . . or low / shorted . . .that's BAD.

Waiting for your findings and feedback . . . . . .

Just now read your add on . . . . .

Your post #16 . . . . confirmed . . . looks like the thermal fuse link is being intact and the resistor blown open
Your post #17 . . . . the thermal coupling / to /mass in no way simulates the attributes of the original product.

" I really want to solder a 10 ohms above the case "

You dont solder to that style of thermal lead as the epoxy embedded wire end will open the internal link 142 deg from soldering iron heat (~200----450 C. )
A person should crimp / screw / spot weld the connection to that critical / temp sensitive lead.



What we can safely . . . SAFELY . . . SAFELY . . . do, is utilize dim lamp technology in the respect of the use of ~40-60 watt / 220/240 V Incandescent lamp inserted in place of the blown thermal resistor.
After checking the board, to be sure that there are being no more shorted diodes and semis in that sby area, one powers up and then watches that lamp .
If it glows bright at power plug in and stays . . . . .still a problem / shorted or breaking down part(s) in that sby area.
If it is dim or lightly glows and tapers on off in brightness. . . progress is then being at hand.

TECHNO REFERENCING SOURCE . . . . .

nsCgkUs.jpg



73's de Edd
 
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Cevi

May 27, 2016
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Sorry for the delay. I am struggling to find the parts online. As for now my best choices are eBay or Aliexpress. They seem to have similar to these items but I am not quite sure.
Could you please check them and tell me if these are the correct ones?
Thanks.

1.The resistor with thermal fuse

https://www.ebay.com/itm/10Ω-5W-RAD...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

2.The Rectifier diode RM11c - (
Which has the same markings but is 2A instead of the original which is 1.2A)
https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20171105032619&SearchText=rm11c

I really don't know is there any substitute for these or they are the only available (genuine) parts for this board. Is there some kind of workaround in case I didn't manage to find them? How can I make the measurements if I don't have that fuse in place. As long as I don't have that line I can't do the measuring right?
Thanks.
 

73's de Edd

Aug 21, 2015
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You are fine on the referenced diodes.
Go back and READ the procedure for EVALUATING the condition of the sets power supply, with the subbing in of the lamp for your testing WITHOUT having to use that resistor/thermal fuse link.
 
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