Philips 42FD9954/17s dead

[ryan74]

Re: Philips 42FD9954/17s dead

ok im back to testing tny256p.
I think I have the correct datasheet.
Is there another way to test this besides hooking everything up and checking volts on each pin?

TNY256P
BP p1= 5.3vdc
S p2= 230mvdc
S p3= 230mvdc
EN/UV p4= 166mvdc
D p5= 169vdc
S p6= 230mvdc
S p7= 230mvdc
s p8= 230mvdc

I dont know if this looks ok

[retiredcaps]

Re: Philips 42FD9954/17s dead

I pulled and checked all 3 varistors with dmm on autorange.
loc3506= 10.7ohm
loc3450= 10.7ohm
loc3451= 9.2ohm
I read under 100ohm is bad.

I'm not suggesting you are making this mistake, but the wording above reminded me of the following situation. Sorry, this story won't add any value to helping with your problem.

I had one person who insisted that she was reading 162V DC on the secondary side of the power board. I told her that she was measuring it incorrectly because every capacitor on the secondary side would have exploded violently if it was really 162V DC.

She wasn't happy with me and thought that by posting a photograph of the multimeter showing the 162V DC reading she would prove me wrong.

After I saw the very fuzzy photo of her autoranging multimeter showing 162.4, I asked her if she knew what the little "m" on the multimeter display meant.

I had to explain to her that the multimeter was displaying 162mV or 0.162V DC.

[ryan74]

Re: Philips 42FD9954/17s dead

I set dmm to resistance (autorange). I think your saying I should have said mohms
I glanced at meter and didn't see the M ohm. I thought the numbers seemed odd but went ahead and posted it.

[retiredcaps]

Re: Philips 42FD9954/17s dead

I set dmm to resistance (autorange). I think your saying I should have said mohms

Like I said, I'm not suggesting you read your multimeter wrong, but every 2 weeks, we get someone saying it tested "good" without posting the actual measurements and/or we get someone posting results with no scale.

Just recently, budm, selldoor and tom66 participated in 11 page, 200+ post thread just to determine if the OP was reading, using and interpreting the multimeter correctly.

PS. And yes, I know the difference between "m" and "M" on the multimeter, but then my story in post #22 wouldn't have made sense.

[budm]

Re: Philips 42FD9954/17s dead

This is another sample of not interpreting the multimeter correctly for dead short, (0.5K)
https://www.badcaps.net/forum/showthread.php?t=24536
So please understand why we ask so many questions since we do not have the board or the meter in front of us to verify.

[ryan74]

Re: Philips 42FD9954/17s dead

I completely understand where your coming from. I'm trying to learn as I go and I know I screw up sometimes. I appreciate corrections and help. I would feel bad if I wasted a lot of time.
I already feel I spent too much time bothering u with this problem and I'm about to give up.

To me it looks like tny256p voltage tested ok but I'm guessing.
Should I retest varistors?
I want to check the small transformer but it is almost impossible to reach the pins and I'm not sure I can test it properly out of circuit.
I may start pulling caps to test.
I'm not sure if I missed something or just haven't found the problem.
I think I need to find an esr meter to test caps in circuit. Any recomendations.

[rayrod81]

Re: Philips 42FD9954/17s dead

If you pulled the varistors out of circuit to test then they are bad. You should recheck them to make sure.

[ryan74]

Re: Philips 42FD9954/17s dead

Im not sure if i tested the varistors correctly before but i found this elsewhere.

"With a DMM you will read a very small capacitance or a VERY high resistance."

Should I test both ways, or is there a better/different way.

[ryan74]

Re: Philips 42FD9954/17s dead

This time I posted pics so I hope I tested correctly. (second pic is capacitance)

If this is good then i may just order the 2 ic and some caps to just try.

Quote(I have seen a couple of these and the TNY265 IC was a problem on both. On one of them I replaced most of the caps, the MC34xxx chip(I can't remember the exact one as I believe there are 2 on the 42" PS), and the TNY256 and it still was not working. What I found was that there was a problem with the varistor where you are seeing the 170V. You will have to pull it out of circuit to test but if the resistance is low then it is bad. It should read very high resistance if not infinite.)

[ryan74]

Re: Philips 42FD9954/17s dead

Im haveing trouble finding parts now.
original:
TNY256P
MC33368P
MC34067P
Varistor-BC 10R 93 131

1)Digikey recommended MC34067PGOS-ND as a replacement for MC34067P.
Can someone verify this?

2)They did not have a replacement for TNY256P or MC33368P.
Can someone help me find replacements?

3)The varistor looks bad and i cant identify it properly or find the part.

[rayrod81]

Re: Philips 42FD9954/17s dead

The ICs are only going to be available on ebay. Most likely they will be coming from china and take a couple of weeks to get here unless they use express shipping. I have ordered from UT Source through ebay a few times and have not received a bad part yet. I will have to take a look at the service manual to see if it identifies the varistor a little better as that code is not bringing anything up on searches.

[ryan74]

Re: Philips 42FD9954/17s dead

I checked ebay and found:

http://www.ebay.com/itm/1-PCS-TNY256...item3cc7363ad1
I assume the tny256pn is an ok replacement, it is all i could find.

http://www.ebay.com/itm/MC33368P-Man...item19d15d841f

http://www.ebay.com/itm/MC34067P-Man...item1c2771baa1

I will order these tomorrow.

[ryan74]

Re: Philips 42FD9954/17s dead

I put a hair dryer on varistor while testing resistance and it went from 11ohm up to 18ohm but then would drop to about 8ohm and repeat. I dont know if thats typical when applying heat.

[selldoor]

Re: Philips 42FD9954/17s dead

Why not post a close up pic of the varistor see if we can interpret the part number

Whilst heat may alter the resistance heat is not what a varistor is about.

http://www.semectech.com/Varistor/


Here is a test

http://0831211.blogspot.co.uk/2012/0...-varistor.html

[ryan74]

Re: Philips 42FD9954/17s dead

here is a pic of varistors(there all the same and apparently bad. pic shows front of 1 and back of another)

I was playing around putting heat at different points.
Pic shows where i heated with hairdryer.
The red led came on so i hit power on remote and at first i got no response. After 10-20seconds the relay would click a few times and try to startup tv. I waited a bit longer and the tv powered on and stayed.

the circled caps i tested with my dmm.
could the parts with arrows to them be the problem?

[budm]

Re: Philips 42FD9954/17s dead

They look like 10 Ohms (10R) Thermistor with Positive temp Cof (Resistance goes up when the temp goes up), not sure what the function of these are for in the circuits, need to see how they are connected.
Varistor (MOV) is for surge suppression.

[selldoor]

Re: Philips 42FD9954/17s dead

I was just thinking that they wouldnt be varistors now we see where they are but could not find a standard marking scheme for thermistors.

Ryan- The red arrows point to inductors - they dont often fail unless they totally burn away. You say you tested the caps with your multimeter - that will not be very accurate unless you took them out of circuit and whilst that capacitance may be ok the esr might not be. Heating them will improve the esr making them work better.
I suggest you change them all unless you can heat individually.

[ryan74]

Re: Philips 42FD9954/17s dead

i check all caps out of circuit. I will start with replaceing the caps.

[ryan74]

Re: Philips 42FD9954/17s dead

I attached the datasheet for the original caps but I have a question.
Other sheets I have looked at in the past have shown imp. along with ripple values. This sheet doesn't show imp. like I have seen before. I see imp. ratio.

one of the caps i want to replace is 16v 470uf 2m067 (8x11.5) ripple=460
this is what i searched for and im thinking the FR series http://www.digikey.com/scripts/dksea...y=0&PV46=13948

How do I determine imp. for replacement? or am I 99% safe with any general purpose with apropriate ripple and dimentions?

Better yet, what series replaced yk so I could just order the new series with the same v. and uf. I still have some trouble with cross referencing caps.

[ryan74]

Re: Philips 42FD9954/17s dead

do these look ok? I tried sticking with panasonic.

Original caps are Rubycon YK series
Original-16v 470uf
http://www.digikey.com/product-detai...2CT-ND/3072222

Original-25v 220uf
http://www.digikey.com/product-detai...2383-ND/613744

Original-16v 1000uf
http://www.digikey.com/product-detai...1CT-ND/3072211

25v 100uf
http://www.digikey.com/product-detai...8CT-ND/3072228