Westinghouse W1603

[Fisher77]

Ok, the power line going into my parents house got zapped by a lighting bolt. It knocked out 3 tv's, a satellite box, satellite dish components, 1 computer, 1 light fixture, 1 light switch, 2 GFCI sockts, and threw just about every breaker in the house. In other words, it did a number on the house. I am hoping to get some help with this tv, and possibly the other 2 tv's. I figure the mobo got zapped on the computer, so it is probably toast.

This Westinghouse is the first of the 3 tv's. I am pretty sure it is something on the power supply. Voltages on the power supply are as follows:

+12V = 0V
+12V = 0V
GND
GND
+3V = 0V
+5V = 0V
GND
GND
On/Off = 0V
DIM = 0V

With those voltages listed I am pretty sure it is something on the power supply. I have checked everything I know how to check on it. There is one diode, D909, that I am getting .018 both ways when I check using the diode check on my DMM. It is in the red box in the pic. The MOSFET Q901 has voltage to the drain. I pulled it off of the board, and checked it. It is switching as it should. I am at a stand still at the moment. Any help will be greatly appreciated.

[budm]

Re: Westinghouse W1603

https://www.badcaps.net/forum/attach...2&d=1481756540
So the black rectangular main AC fuse by the grey rectangular capacitor is good?
What is the DCV between the two legs of the main filter cap, the big cap laying on its side?It should have around 160VDC between the two legs.

[Fisher77]

Re: Westinghouse W1603

Yes the fuse is good. The main filter cap has 164VDC. Drain of the FET has the same voltage as the cap.

[budm]

Re: Westinghouse W1603

OK, so it has the main DC to run the SMPS circuit but it is not running right now.
Boards for your TV are cheap.
http://www.shopjimmy.com/catalogsear...inghouse+W1603

[Fisher77]

Re: Westinghouse W1603

Yep, the SMPS is dead as a door nail. One thing that I just thought of that I didnt check is to see if there is any voltage at the switch mode transformer. Anything stick out to you that could be the problem budm?


$14 is not bad at all for the PS board. Question is, did it get the main board to. I would like to get the PS working to see, but I may just have to take the chance and order the PS.

[budm]

Re: Westinghouse W1603

The chance that main board is bad is very possible, I would spend 14 Dollars on the power supply first an go from there.
To do more in depth troubleshooting of the power board I will have look at the board in details and trace out the connection to get the test points for you to test.

[Fisher77]

Re: Westinghouse W1603

Thanks budm. I will start checking the next tv in the mean time. If I end up having to order multiple boards from shopjimmy, I would rather order them all at once. I appreciate it.

[Fisher77]

Re: Westinghouse W1603

I was probing around on the PS this morning. I tested continuity on all the pins of the T901. They all had continuity between each other. I then tested from the + of C930 to all the pins, and again they all had continuity. That don't seem right.

Here is a pic with he points I tested: https://i.imgsafe.org/2eefae445a.jpg

[budm]

Re: Westinghouse W1603

The secondary side windings (2) will show very low DCR and they are connected together through thee traces on the board.
So what resistance do you have between the two legs of C930 that you have marked in the picture? If it shows <5 Ohms then that is bad, something is bad in that section.
D904 common Cathode diode may be shorted out..

[Fisher77]

Re: Westinghouse W1603

Ok, if I got positive lead to positive of the cap, neg lead to neg, it crawls up to about 3.5K, then starts falling. If I reverse the test leads to the cap it shows 0.947K. Let me know if I am doing this right.

[budm]

Re: Westinghouse W1603

I was probing around on the PS this morning. I tested continuity on all the pins of the T901. They all had continuity between each other. I then tested from the + of C930 to all the pins, and again they all had continuity. That don't seem right.

Here is a pic with he points I tested: https://i.imgsafe.org/2eefae445a.jpg

OK, when you use the word continuity, what are the actual resistance readings in Ohms? Continuity is only good for telling you that the path between point A and Point B is not open circuit but you need to read the resistance reading to find out if the resistance between point A and point B is a dead short or it has some resistance between the two points.
It does sound like you have short circuit in that section since the resistance reading between the two legs of the cap is at at steady low resistance of < 5 ohms or so.

[Fisher77]

Re: Westinghouse W1603

Continuity with the buzzer, no ohms reading. I will check the resistance and post back.

[Fisher77]

Re: Westinghouse W1603

Ok, From the positive leg of the of the cap to the negative leg on the transformer it is reading 4.35K ohms. That is after it goes up to 3.998 and then drops back down to 4.35K.

[budm]

Re: Westinghouse W1603

Those readings are fine.

[Fisher77]

Re: Westinghouse W1603

Is it possible that IC901 could be toast. It looks to be what drives the Q901 MOSFET. It is a LD7575PS.
Here is the datasheet for it: https://cdn.badcaps-static.com/pdfs/...6df169e617.pdf

I took some voltage measurements at each pin:
1:0V has resistor to ground of 100K to set the switching frequency. It is ohming at 100K.
2:0V - connected to the photocoupler. Photo coupler has 0V as well.
3:0V - connected to the souce of the MOSFET
4:GND
5:0V - connected to the gate of the MOSFET
6:11.6VDC - is within spec according to the datasheet
7:NC
8:145VDC

[budm]

Re: Westinghouse W1603

I forget to ask you if you run the power supply/inverter board by itself, do you get any DC on the output pin?

[Fisher77]

Re: Westinghouse W1603

I forget to ask you if you run the power supply/inverter board by itself, do you get any DC on the output pin?

Can you tell me how to do that budm?

[budm]

Re: Westinghouse W1603

Just disconnect the cable from the power supply board to the main board and then apply AC to power the power supply board, this power supply is an always on power supply so when you apply AC to the board you should then see some DCV at the pins of the connector that goes to the main board.

[Fisher77]

Re: Westinghouse W1603

Ok, it has 0V on the output pins.

[budm]

Re: Westinghouse W1603

Check the brown resistor with 0.62 Ohms printed on it to see if it still shows <1 Ohm.