tv repair help

[wraper]

I don't know witch one is the collector anyway.

You can figure it out by whith other parts are connected to tat pin according to schematic. For example, if pin of Q9503 is connected to Q9502 and R9521, this is collector. And Usually collector is single pin in the middle of smd transistor. Look at the picture.

[snipersquad100]

which one is the collector lol, 1 2 or 3. I cant find a datasheet on it as It got no number.

[snipersquad100]

oh ok ingnor that 123 pic

[snipersquad100]

ok, C of Q9503 = 0.01v
     C of Q9502 = 4.5v
     E of Q9507 = 17.2
and pin 8 of Ic9502 = 17v

[tom66]

Whereabouts are you in the UK? If you're near me, I would actually pay money for this faulty set as described. If you give up on it...
Your ground for primary side where do you have it?

[snipersquad100]

im in Swansea. I used the -side on bridge rectifier as it says gnd1 on the schematic.

[wraper]

In that section everything seems OK. As I understand at the same time there is only 330V on 375V rail. So I need some more checks. Please measure voltage between GND1 and pin 1 of IC9502. Then measure voltage across C9503 and across C9501. If voltage across capacitors is almost the same (what means PFC is really dead), switch TV off and then measure resistance of K9502 fuse, R9529, R9530, R9502. Be sure That C9501 discharges before measuring those resistors and fuse.

[tom66]

im in Swansea. I used the -side on bridge rectifier as it says gnd1 on the schematic.

Lol, OK. Leeds. I used to live down near Reading so I would pick it up otherwise. But anyway, even if you decide to get rid of it, it will be gone the next day if listed on gumtree for £30 as faulty...
The HIGH ignal at collector of Q9502 is good, this will turn on Q9508 which should turn on Q9507.
So what do you get at C of Q9507?

[snipersquad100]

Gnd 1 to pin1 of Ic9502 = 2.5v
C of Q9507 = 17v
V across C9503 = 330v
V across C9501 = 332v
Resistance
K9502 = 0.09 ohms
R9529 = 100 ohms
R9530 = 22.09 ohms
R9502 = 0.2 ohms

[tom66]

You should have 375V if that is as it is. If not, IC9502 may be defective, you replaced it? If so check C9502 for int short, try flexing it.

[wraper]

Strange that there is 2,5V on pin 1 as there should be 2,5 at 375V output as it is feedback pin and only 2,2V on 330V. So Either there is something wrong with sense voltage divider or ic9502 is dead. Check R9514 and R9515. Their resistance in paralel should be 16,6 kOhm, however surrounding circuit can influence it. Check also R9512, R9513, R9516. I think we are very close to find the fault.

[snipersquad100]

R9514 = 16.2 ohms
R9515 = 16.2 ohms
R9512 = 828k ohms
R9513 = 780k Ohms
R9516 = 780k Ohms

the last 3 readings were up and down, might be cos they in circuit.

[tom66]

Do you mean 16.2 kohm or 16.2 ohm really?

[snipersquad100]

16.2k sorry on both

[snipersquad100]

yea I changed that ic today same fault. yesterday I paralleled up that big cap with a 470uF 450v cap, no change. its tight to the pcb and solder looks ok, I did resolder it yesterday too. 

[snipersquad100]

c9501 I ment, I check c9502 now

[wraper]

R9512 = 828k ohms
R9513 = 780k Ohms
R9516 = 780k Ohms

the last 3 readings were up and down, might be cos they in circuit.

That's strange, because they are in series and all 820K so should read the same even in circuit. Try to desolder R9512 and check resistance. Then check 2 remaining resistors as they are no longer connected to the circuit and must read real value.  Look also what is written on them, they should be the same 820k but who knows. And measure R9514 again before soldering R9512 back.

[snipersquad100]

ok,
R9512 = 822k numbered 824
R9513  = 787k   nr    824
R9516  = 778k   nr    824
that's not right surely ?

[wraper]

Yeah, 2 resistors are way off, and strangely to lower side what is not usual. Thats seems to be the fault. Replace all 3 to new ones as there is potential that 3rd resistor will go bad later. Better use 1% resistors as a replacement or if you use 5% ones check them before soldering that total value of them in series would be not worse than 2460 kOhm +-1%

[snipersquad100]

im going to have to order them, unless I bodge it up with throu hole lol

[wraper]

im going to have to order them, unless I bodge it up with throu hole lol

Well, you can bodge temporarily to see how it works.

[snipersquad100]

The 375v rail has gone from 345 to 383volts, ive just turned it on, fingers crossed, touch wood lol.

[snipersquad100]

It's Still on, I think it's safe to say its fixed.
Thank you guys.

[wraper]

Happy for your succesfull repair 

[tom66]

Nice, interesting to see the failure of the resistors to decrease in value rather than the typical increase due to excessive heat.