Olevia 342-B11 PSU problem, No voltage in secondary PSU

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

So although the - and ac (~) leads give diode readings when the leads are aranged either way , the bridge rec is still fine? Is this because while still on the board you just look for different diode / voltage readings when you reverse the leads?

like 1-2 was reading .562
and 2-1 was reading .575
That is acceptable when its still on the board?
And the - and + pins being continous / closed while its still on the board?

Additionally what should be my next step be to test this board?

[PlainBill]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

So although the - and ac (~) leads give diode readings when the leads are aranged either way , the bridge rec is still fine? Is this because while still on the board you just look for different diode / voltage readings when you reverse the leads?

like 1-2 was reading .562
and 2-1 was reading .575
That is acceptable when its still on the board?
And the - and + pins being continous / closed while its still on the board?

Additionally what should be my next step be to test this board?

I've attached a drawing of a diode bridge. A good bridge rectifier out of circuit would show about a .5 to .7 volt diode drop from 2-1 and 3-1. (1 negative and 2 and 3 positive). It would show the same drop from 4-2 and 4-3. (4 positive and 2 and 3 negative). It should show a roughly 1 - 1.4 volt (2 diodes) drop from 4-1. All other readings would show open because the diode was reverse biased. HOWEVER, if 1 and 4 are shorted, things get messy, you won't get open readings, but you will still get the forward diode drops.

What is inexplicable about this is there are only two things that can cause a short - the large cap or the FET.

As for what to do, remove them and test. Also, look for some additional components that may be shorting the output of the diode bridge.

PlainBill

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

I actually in the mean time tested the other FET's that are mounted on the aluminum heatsinks.

There are 4 items mounted on the heatsink with the "melting" FET.
From right to left when looking at the top of the board the first 2 are transistors and appear like they might be broke because of the readings i got.
Then there is a diode, and finally the "melting" FET that i gave you readings on earlier.

The furthest right fet has 0 resistance on all 3 leads in all combinations and orders, I cant imagine there would be any use for a part that just connects all 3 leads lol.

The next fet over had some similarly odd readings, but not in every order.

And thanks for all your help so far, ill probably pull some of these transistors off shortly to test them unless you think thats a bad idea.

Attached is 2 pics of the "melted" FET the melted part is on the bottom right, and then a pic of all 4 FETs in a row on the heatsink.

[PlainBill]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

I actually in the mean time tested the other FET's that are mounted on the aluminum heatsinks.

There are 4 items mounted on the heatsink with the "melting" FET.
From right to left when looking at the top of the board the first 2 are transistors and appear like they might be broke because of the readings i got.
Then there is a diode, and finally the "melting" FET that i gave you readings on earlier.

The furthest right fet has 0 resistance on all 3 leads in all combinations and orders, I cant imagine there would be any use for a part that just connects all 3 leads lol.

The next fet over had some similarly odd readings, but not in every order.

And thanks for all your help so far, ill probably pull some of these transistors off shortly to test them unless you think thats a bad idea.

Attached is 2 pics of the "melted" FET the melted part is on the bottom right, and then a pic of all 4 FETs in a row on the heatsink.

Part of the mystery has been solved. I was loosing sight of the overall supply. This supply has a PFC front end, which complicates the picture significantly.

While the pictures are pretty good, they don't show quite enough detail. There are two heat sinks on the hot side of the power supply. The one with the diode bridge has two transistors that drive the main SMPS transformer. The other one is more interesting. There are two three-legged components (transistors?) that appear to be associated with the PFC front end, a diode, and the 'melted FET'. What are the component identifiers on these, and (more important), the part numbers?

PlainBill

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

First aluminum heatsink:
BD1) (bridge rec) pec 704v RU(logo), KBU 8J, - ~ ~ +
Q2) S (sylized for brand logo), K3569, 7:E
Q1) same as Q2

Second aluminum heatsink:
Q3) f(sylized like fisher scientific's f) M H10, F0PF, 13NF0C
Q4) same as q3
D7) STTH8L0bFP, GK1AN VU, CHN 719, ST (logo)
Q5) (brand logo) H , 04N70BF, 7 1509(1)< melted fet so hard to read last #

Q3 and Q4 are the ones i suspected of possibly being bad
Q3 has all 3 pins reading 0 ohms / continuous / 0 voltage diode reading
Q4 has 3-2 2-3 reading 0 ohms / continuous / 0 voltage diode reading
pins being numbered from left to right when your looking at the markings.

So am i right to assume this short must be occuring in the primary side of the powers supply, because anything occuring after the transformers would not be able to blow the AC fuse?

Hope your having a good weekend

[PlainBill]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

First aluminum heatsink:
BD1) (bridge rec) pec 704v RU(logo), KBU 8J, - ~ ~ +
Q2) S (sylized for brand logo), K3569, 7:E
Q1) same as Q2

Second aluminum heatsink:
Q3) f(sylized like fisher scientific's f) M H10, F0PF, 13NF0C
Q4) same as q3
D7) STTH8L0bFP, GK1AN VU, CHN 719, ST (logo)
Q5) (brand logo) H , 04N70BF, 7 1509(1)< melted fet so hard to read last #

Q3 and Q4 are the ones i suspected of possibly being bad
Q3 has all 3 pins reading 0 ohms / continuous / 0 voltage diode reading
Q4 has 3-2 2-3 reading 0 ohms / continuous / 0 voltage diode reading
pins being numbered from left to right when your looking at the markings.

So am i right to assume this short must be occuring in the primary side of the powers supply, because anything occuring after the transformers would not be able to blow the AC fuse?

Hope your having a good weekend

Q5 is easy - it's an AP04N70BF-A power FET

Q3 and Q4 sound like either Fairchild of Fujitsu part numbers, but I haven't been able to get hits on the numbers you gave.

Right, the short is occurring on the primary side of the transformers.

Weekend has been mostly disappointing. Still, it beats the alternative.

PlainBill

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

I checked both brands on ebay and the logo was fod fairchild. Figured out what i read as a 0 must have been Q as well as some other errors...
So im pretty sure the part number is fairchild fqpf13n50c.

Digi key has FQPF13N50CF-ND for sale as well which is probably similar.

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

A question mostly out of curiousity : theres a transformer located in the middle of the primary side, is this involved in the primary side, or just because they had some extra space there. Or is it on the primary side because its the 5v transformer for the standby so always runs?

Assuming i can find somewhere to buy the AP04N70BF should i pull off the 3 FET's that appear to possibly be bad and then test them again and replace if bad? Are there likely to be other smaller parts that went out with these parts?

[PlainBill]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

A question mostly out of curiousity : theres a transformer located in the middle of the primary side, is this involved in the primary side, or just because they had some extra space there. Or is it on the primary side because its the 5v transformer for the standby so always runs?

Assuming i can find somewhere to buy the AP04N70BF should i pull off the 3 FET's that appear to possibly be bad and then test them again and replace if bad? Are there likely to be other smaller parts that went out with these parts?

If you look, there is a black line that runs across the board, and two transformers straddle this line. The smaller of those two is part of the standby SMPS; the larger is part of the main SMPS. The third 'transformer' is part of the PFC circuit.

The failures puzzle me. I can see the pair of FETS shorting if one fails - they are in a totem pole configuration. I don't understand the FET for the standby SMPS shorting as a victim of the others shorting, or causing the others to short.

PlainBill

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

Well the 3rd FET that handles the standby as far as i can tell isnt shorted, it gives normal readings (all over 200ohm resistance, and diode voltage readings for only 2 combinations of pins , and no readings when i reverse the leads).

It is "melted" though at the bottom, which i think is why you are thinking i was saying it was shorted, though it appears to be still working fine although there is a little melting... and it does run all day and so perhaps melts / goes bad over time.

I figured because it was melting and blew up on the other guy that you were recomending replacing it. But since its hard to get one / and appears to still be working i might be ok with just keeping it? The fuse blows on me before turning on the tv as well, just from connecting the power. So idk if that means the problem cant be with the pair of FET's and has to be with something involved in the standby power?

[PlainBill]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

Well the 3rd FET that handles the standby as far as i can tell isnt shorted, it gives normal readings (all over 200ohm resistance, and diode voltage readings for only 2 combinations of pins , and no readings when i reverse the leads).

It is "melted" though at the bottom, which i think is why you are thinking i was saying it was shorted, though it appears to be still working fine although there is a little melting... and it does run all day and so perhaps melts / goes bad over time.

I figured because it was melting and blew up on the other guy that you were recomending replacing it. But since its hard to get one / and appears to still be working i might be ok with just keeping it? The fuse blows on me before turning on the tv as well, just from connecting the power. So idk if that means the problem cant be with the pair of FET's and has to be with something involved in the standby power?

I'm sure the FETs are part of the PFC circuit and are responsible for the fuse blowing. I've been wracking my brain for a typical schematic when I realized there is an easier way. There are three ICs on the bottom of the board. Two of those are the standby and main SMPS controller, the third is the PFC controller. What is the part number of IC3?

PlainBill

[Robbiebaby]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

I have a 42" olevia that uses the same power supply (fsp271-4f02) although its a different model.

When I bought it to fix it had a blown main ac fuse which I replaced and it instantly blew when I reconnected the power. According to fixya this is probably a transistor in the primary section of the board which I tend to believe since all the caps look perfect (very rare for capxcons). What kind of reading should I take to isolate the bad transistor. I'm guessing the IC he has been probing is the one in the middle on the back side of the board and I should use pin 4 as the negative... But with the fuse blowing instantly this is impossible. Should I be looking for continuity from both outer leads of a transistor to indicate a short? (Totally guessing here).

Ok, im back, and interestingly enough, I have the exact same problem as this fellow mentions now, except I'm almost 100% sure that its because the IC2 I received from mouser to replace the original was actually a model 203D6...and NOT the 230D6 that I needed.....Which, after reviewing the past posts on this thread. I realized that the conversation derailed when I said that mouser had the SMPS in stock (203D6)....except I think when searching for it I had a typo with the numbers....clumsy me hehe.

Anyways, I realized my mistake when I soldered it on, The fuse blew, and continued to blow when I replaced the fuse....I took off the SMPS and it still blows. I checked Q5 the, original problem MOSFET from the first post I had, and according to you're guide on checking them, its showing diode readings on all the leads no matter the arrangement. I'm sure its shorted...again... Either way, I'm still deciding if I should continue replacing components, or if I should just throw in the towel on this one, since finding another Q5 AP04N70BF was almost impossible the first time around.

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

Ill split 1000 AP04N70BF with you! Doesnt hurt to have extras! might cost like 300 dollars for the each of us! j/j

BTW has anyone on this forum bought something through hkin (sorry to mention the name of a probably not approved supplier) the site looks more for trading large stocks of components then for small purchases. If you search there for AP04N70 you get a few companies with various models including a lot with AP04N70BF-A.

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

The IC3 for the pfc section is marked 28051, 72M, CK4M
In the middle line before the 72M there is a U with a line under it, theres also a | on the left side of the chip but it doesnt look to be part of a logo. Hard to tell.

Looks like 28051 is a common PFC controller design that TI probably made, but this isnt a TI chip but some sort of cheap remake of it,below is a picture of a rather similar chip, although even that is somewhat different.

http://www.aliexpress.com/fm-store/9...LER-SOIC8.html

[PlainBill]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

The IC3 for the pfc section is marked 28051, 72M, CK4M
In the middle line before the 72M there is a U with a line under it, theres also a | on the left side of the chip but it doesnt look to be part of a logo. Hard to tell.

Looks like 28051 is a common PFC controller design that TI probably made, but this isnt a TI chip but some sort of cheap remake of it,below is a picture of a rather similar chip, although even that is somewhat different.

http://www.aliexpress.com/fm-store/9...LER-SOIC8.html

Thanks, I'll have to look at the pictures later, but a shorted PFC FET could certainly cause the fuse to blow.

PlainBill

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

Q4 has the emiter and colector continous, but thats understandable since i know the + and - are shorted.

Q3 on the other hand has the gate continous with the collector and emiter.

I tried to follow the path of the gates back to the IC, and it appears it goes to what is marked as pin 7 drv in the data sheets. On the way from the gate to the IC there are a few small resistors and diodes, then a transistor whose gate is controlled by the IC pin 7. The small transistor (Q10) for the gate of Q3 is continous between its collector and emiter, while the small transitor(Q13) for Q4 isnt. So Im not sure how i would elimite whether its really Q10 thats bad or Q3.

``````````````````````````````````____ (+)
```````````````````________(Q3) g /
IC pin 7 ___ (Q10) g /```````````````\
```````\``````````\___(-)``````````\___(-)
````````\`````````/````````````````/
`````````\_(Q13)`g ```````````````/
`````````````````\_________(Q4)g \_______(+)

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

If q10 was at fault i would still get a diode reading between q10's connection to the negative and q3's connection to the positive. So i think i can assume q3 is bad?

I think im going to have to draw all possible paths... damn it... i always prided myself in physics for being able to just imagine the circuits in my head instead of drawing them ...

And for diode readings on q10 i get different voltage drops for gate to collector vs collector to gate, and different voltage drops for emitter to gate and gate to emitter. I do get voltage drops both directions (when reversing the leads) though.

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

Well i took off Q3 (QPF13N50C) and the board isnt shorted once it is removed, and the now removed FET tested bad like expected.

So i guess i will order FQPF13N50CF-ND from digikey, Is that the same part as what i removed? even though it has extra letters at the end. Should i replace both while im at it? Are FET's very heat sensitive, and so should i solder them in quickly / with as little heat as possible?, And finally is arctic silver ceramique an acceptable thermal greese for the FET to the heatsink?

[PlainBill]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

Well i took off Q3 (QPF13N50C) and the board isnt shorted once it is removed, and the now removed FET tested bad like expected.

So i guess i will order FQPF13N50CF-ND from digikey, Is that the same part as what i removed? even though it has extra letters at the end.

Yes

Should i replace both while im at it?

Definitely.

Are FET's very heat sensitive, and so should i solder them in quickly / with as little heat as possible?,

They are not terribly heat sensitive, but if you spend so much time soldering it in the heat sink gets hot, there is a problem.

And finally is arctic silver ceramique an acceptable thermal greese for the FET to the heatsink?

IMHO, it's overkill. But I'm from the time when a mica washer was considered good enough.

PlainBill

[cashkennedy]

Re: Olevia 342-B11 PSU problem, No voltage in secondary PSU

IMHO, it's overkill. But I'm from the time when a mica washer was considered good enough.

Overkill is taking off all the other FET's and diodes on the heatsinks and replacing with arctic silver 5.

Im kinda anal, and so although ill never see the power supply once the back is on the TV. I wouldnt want the thermal grease's to be different colors. Luckily ceramique is white like the original.

Good to know about the heat, the datasheet actually listed 300c max which sounded crazy low to me at first, then i remebered my iron is ~800f, not 800c. Maybe once you oldies are gone we can finally switch to celsius... j/j

Thanks for all your help hopefully by the end of the week, we will know if things worked out.