LG42pa4500, YSUS problem

Witam, próbuje naprawić telewizory lg42pa4500.
W tv brak napięcia 205V(Vs). Okazało się że płytce YSUS, napięcie to jest zawarte do masy. Wymieniłem uszkodzone elementy (dioda UF4007, mosfet KF7N60 oraz jeden z pary mosfetów RJP30H2A(uszkodzony). Sądziłem, że wszystko ruszy od kopa. Po podpięciu zasilania ponownie uszkodziły się dioda UF4007, mosfet KF7N60 oraz drugi nie zmieniony mosfetRJP30H2A.

Ktoś ma pomysł gdzie szukać przyczyny??


Ps.
Po ponownej wymianie elementów
Dziwi mnie taka sytuacja (gniazdo pomiarowe VS jest zawarte to masy ) rysunek poniżej.


Na czerwono zawarte gniazdo pomiarowe VS, na zielono drugie które ma właściwą rezystancję

Hello!

Please post a clear picture from bottom side of the board with highlighted damaged components.

Damaged components:


There should be RJP30H2A

Please, post a clear pictures with visible markings on highlighted chips (picture below).

Arni wrote:[ Obrazek ]
[ Obrazek ]
[ Obrazek ]

I can't see any markings on the requested components from these pictures.

I cant make better fotos. This is my best shots

Check the transistor highlighted with blue (upper picture). It is a PNP bipolar transistor.


Check the chips highlighted with red (upper picture). There are actually an NPN + PNP transistors inside it.


Measure the resistances between listed pins of chips marked with yellow. They are marked as "A", "B", "C" (upper picture)
- Between pin 4 and pin 5.
- Between pin 5 and pin 6.

Chips "A", "B", "C" pin count:

BLUE
E-B 50KΩ
E-C 10KΩ
B-C 39KΩ

A
4-5 107KΩ
5-6 OL
B
4-5 1700KΩ
5-6 OL
C
4-5 1650KΩ
5-6 OL

RED LEFT
1-2 OL
1-3 0.4
1-4 OL
1-5 OL
2-3 1700KΩ
2-4 90KΩ
2-5 10KΩ
3-4 OL
3-5 OL
4-5 82KΩ

RED RIGHT
1-2 OL
1-3 0.4
1-4 OL
1-5 OL
2-3 1710KΩ
2-4 15KΩ
2-5 10KΩ
3-4 OL
3-5 OL
4-5 4.5KΩ

Are all other power transistors and power diodes on the board functional?

matic wrote:Are all other power transistors and power diodes on the board functional?

Yes, I didint found any damaged part.
But how to prevent next dmg of that parts? If somthing go wrong? Any Idea?

Remove tre transistors highlighted with blue and red (picture from post #8) from the board and check them outside of the board.

We check the bipolar transistors with a multimeter set on the "diode test" mode.
To check them, measure the voltage drop between the B-C, B-E and C-E of each transistor with both polarities of test leads.
B= Base
C= Collector
E= Emitter

Are there any options to check this under low volting Like 20-30V or maybe put somewhere fuse? Becasu I think this was just bad luck with secend blow.

Arni wrote:Are there any options to check this under low volting Like 20-30V or maybe put somewhere fuse?

No, there aren't.

Please, check the transistors as suggested.

BLUE:
+ -
B-C OL
B-E 700
C-E 700
C-B OL
E-B OL
E-C OL

RED I USED THIS SCHEMATIC


LEFT RED

+ -
B-C (5-1) 750
B-C (5-2) OL
B-E (5-4) 750
B-C (3-1) OL
B-C (3-2) OL
B-E (3-4) OL
C-E (1-4) OL
C-E (2-4) OL
DIRECTION
- +
B-C (5-1) OL
B-C (5-2) OL
B-E (5-4) OL
B-C (3-1) OL
B-C (3-2) 730
B-E (3-4) 730
C-E (1-4) OL
C-E (2-4) OL

RIGHT RED

+ -
B-C (5-1) 745
B-C (5-2) OL
B-E (5-4) 750
B-C (3-1) OL
B-C (3-2) OL
B-E (3-4) OL
C-E (1-4) OL
C-E (2-4) OL
DIRECTION
- +
B-C (5-1) OL
B-C (5-2) OL
B-E (5-4) OL
B-C (3-1) OL
B-C (3-2) 730
B-E (3-4) 730
C-E (1-4) OL
C-E (2-4) OL

No one give me answers so I decideted to try run it. Its blow again

Now I noticed Spark here:


Destroyed elements(2): again diode and KF7N60.
and One more KF7N60
What's more I found somthing weird:
That transformer T501

Have 0.4Ω on first leg. Why?

All of the voltage drops measurements on the "red" (5-pin) transistors are not as it should be. You also performed some of the measurements between the wrong pins.

First off all I suggest you to use the suggested pin count (picture below), because it is the most standard for all components in such package.


Measure the voltage drop between listed pins (according to the upper pin count) in both directions (+ -) and also (- +) of both "red transistors".
a) 1-2
b) 1-5
c) 2-5
d) 3-2
e) 3-4
f) 2-4

Arni wrote:What's more I found somthing weird:
That transformer T501
[ Obrazek ]
Have 0.4Ω on first leg. Why?

If you mean the resistance to ground, the reason is trivial - this pin is connected directly to the ground.

matic wrote:Measure the voltage drop between listed pins (according to the upper pin count) in both directions (+ -) and also (- +) of both "red transistors".
a) 1-2
b) 1-5
c) 2-5
d) 3-2
e) 3-4
f) 2-4

Red (both identical measurements):
a) 1-2 =OL
2-1 =730
b) 1-5 =OL
5-1 = 730
c) 2-5 = OL
5-2 =OL
d) 3-2 =750
2-3 =OL
e) 3-4 =750
4-3 =OL
f) 2-4 =OL
4-2 =OL

Check the highlighted resistors (pictures below).

Pictures 1- 15.4Ω
Pictures 2 :
From LEFT
27Ω
27Ω
10k Ω
27Ω
27Ω