Repair SMPS - Need help identifying SMD, schematic attached

[silversweden]

Hello folks!
I need some help identifying a SMD transistor. Q119 on schematic.
Schematic of SMPS on Page 129 and 131. www.itxpress.se/433cmx.pdf

It says "YA" on top of the SMD transistor Q119.
And it is a SOT23 package or similar.
It should be a FET according to schematic.

On most sites i find that YA is a pnp wich is faulty according to schematic.

But then i found this site:
http://www.ginko.de/user/franz.hamberger/infobase/charts/smdcode/cy.html

It says YAs = BSS83P wich is a SIPMOS, could this be correct?
Maybe i can use BSS84? Dont know if this part is critical.

The reason i want to replace it is because it reads a low Ohm.
R133 are burnt and Q125 shorted, probably because Q119
failed. Anyone who can confirm or dismiss my theory?

Any help here would be great though!

 

[scott wurcer]

You need to ID the maker, AFAIK the codes are only unique within one companies product line and should be on their datasheet. With some really tiny packages the ID is only on the strip carrier or shipping bag so you need the schematic.

 

[silversweden]

I posted a link to the schematic. It does not say what they are.
Just a schematic. I think pioneer bought the power board
from someone else to power PDP. All components on the
other schematics for the different boards is written out.

But not the Power Supply

What should i do?

 

[Lumba Ogir]

silversweden,
BSS83P and BSS84 are PMOS. You need NMOS.

 

[silversweden]

I really cant find the original part number
Wich NMOS could i replace this with?

 

[Lumba Ogir]

silversweden,
I don`t think a part number exists. YA is probably just some kind of internal designation or production code.
Try some NMOS you can get.

 

[silversweden]

Yippie! I found it =) i think. on this site, dont understand the language.
http://monitor.net.ru/forum/plasma-pioneer-pdp-503mxe-info-114977.html

just saw what YA = 3LN01C wich is a NMOS

maybe they just suggested that part... dont know

 

[Lumba Ogir]

That`s a real audiophile-grade device.

 

[silversweden]

okey but do you think it will work?

 

[Lumba Ogir]

It definitely will. My assumption was wrong, the marking is confirmed in the datasheet. It`s the device.

 

[silversweden]

I found out that YA is probably a 3LN01C wich is a n-channel mos.
I really cant get that exact modell, is it that criticall you think?

If i find a fet with higher Vds Id and about the same Ohm would that be OK?
I was looking at the 2n7000 wich is really easy for me to get and cheap.
www.itxpress.se/2n7000.pdf <--good replacement for ? www.itxpress.se/3LN01C.pdf

This is the driver for the Q125 wich is a 2sk2651 www.itxpress.se/2sk2651.pdf

Is it a possible theory that fet driver 2n7000 failed caused overcurrent to
Q125 (2sk2651) wich caused it to short causing the burnt R133 0.1 ohm
resistor in the "supply" line to blow, or is it more to it?

I have learnt that you should never just replace the part blown and think it should
work. By the way, 2sk2651, im thinking of changing this to something more easy
to obtain, is this critical? Is there any good books describing finding replacements
for different applications not just saying "find something similar according to Voltage
Current Switch time and so on...."

 

[Lumba Ogir]

silversweden,
sorry but I don`t have any motivation for taking a further active interest in this problem. Hopefully, you will find a solution after some experimentation.
Merry Christmas.

 

[silversweden]

Okay, i replaced the faulty components wich i know of.
R133, Q125 and Q119.

I plugged the board in and still no power!
Nothing happens, ALARM LED D124 lits up red.

No relay clicking nothing.

The one thing i do have is the 5V STB which in
fact is, 5.1V.

How do you troubleshoot this kind of a thing
when you dont even have voltages???