Sony SMD-HS73

[torin3]

Re: Sony SMD-HS73

I have noticed what is being displayed on the screen, May be hard to see even with a flash light. If you could display a web page with several different colors, writing pictures ect.it May it be easier for you to see?

Nearly white web page window, moving it around on the monitor with a dark green background. When the lamps are off, I can't see anything.

Also, sometimes when the lamps are on, there is no picture on the display.

When the lamps are on, screen is sometimes 'rolled' (top half of image is on the bottom half of the screen, and bottom half of the image is on the top half of the screen. Orientation correct, but like the vertical hold is off.)

[torin3]

Re: Sony SMD-HS73

I haven't done this test myself, but plug in the lcd into the wall outlet/power bar with power off. Measure the DC voltage at the ON/OFF on CN1.

Now turn on the power LED, what is the voltage? When the backlights go off, what is the voltage?

So you should have 3 readings.

Also, try alexanna's suggestion in post #43.

Off = .12V
On = .14V
Light on, hard to tell with my slow meter, but it looks like close to 5V.

[retiredcaps]

Re: Sony SMD-HS73

CN1 legend:
ON/OFF

I haven't done this test myself, but plug in the lcd into the wall outlet/power bar with power off. Measure the DC voltage at the ON/OFF on CN1.

Now turn on the power LED, what is the voltage? When the backlights go off, what is the voltage?

So you should have 3 readings.

Also, try alexanna's suggestion in post #43.

[torin3]

Re: Sony SMD-HS73

U2 and U3 test/look fine. You would need to test out of circuit if the readings are less than 30 ohms.

That is what I thought, but I wanted to make sure. Just got back home and I'm a little tired.

[retiredcaps]

Re: Sony SMD-HS73

Would I need to test out of the circuit if all are over 30 ohm?

U2 and U3 test/look fine. You would need to test out of circuit if the readings are less than 30 ohms.

[torin3]

Re: Sony SMD-HS73

Datasheet for 4542 is at

http://pdf1.alldatasheet.com/datashe.../KI4542DY.html

Let's see if U2 and U3 are good?

If any ohm reading is less than 30 ohm you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Would I need to test out of the circuit if all are over 30 ohm?

-------U2----U3
S1-G1 100K 100K
S1-D1 OOR  OOR
G1-D1 OOR  OOR

s2-G2 736  737
S2-D2 460  460
G2-D2 72K  72K

OOR = Out Of Range on the 2000K selection

[alexanna]

Re: Sony SMD-HS73

Did you ever verify that you can see an image if you shine a flashlight on the screen? The logic board is getting 5V and the voltage regs are working, therefore, you should at least get an image.

I have noticed what is being displayed on the screen, May be hard to see even with a flash light. If you could display a web page with several different colors, writing pictures ect.it May it be easier for you to see?

[retiredcaps]

Re: Sony SMD-HS73

U2 = 4542 / (logo)AD(Delta smbol) / W37A
U3 = same as U2

Datasheet for 4542 is at

http://pdf1.alldatasheet.com/datashe.../KI4542DY.html

Let's see if U2 and U3 are good?

If any ohm reading is less than 30 ohm you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

Simply test

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms

Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.

edit: Just thinking out aloud, what if just one of them is bad? Would that explain the backlight off/on?

[torin3]

Re: Sony SMD-HS73

This is a low probability, but just for my own curiousity, can you carefully measure the voltage across the main filter capacitor (the big one) and see if you get steady DC voltage?

You are looking for a steady voltage while the screen is flickering. You can use the original ccfls for this test.

For this test, I like to use aligator clips with my multimeter so I can do this measurement without using my hands. It is high voltage that you will be measuring (about 165V DC).

When the lamps are off, it read 153.6 to 154.6 VDC. When the lamp flicks on, it drops down to roughly 150 VDC. The lamp doesn't usually stay on long enough to get a very precise reading with my DMM.

Did you ever verify that you can see an image if you shine a flashlight on the screen? The logic board is getting 5V and the voltage regs are working, therefore, you should at least get an image.

Sorry if I wasn't clearer before. When it goes dark, there is no picture visible on the screen with a bright light. I might not have a bright enough light, but given that it changes resolution occasionally, I'm pretty sure there is no picture when the lamps are off.

I did try again with the spare good CCFLs. I couldn't tell any color/brightness differences per plug for sure. I'm going to try and readjust the wiring so I can have a lamp on each side at the same time to have them next to each other to compare, just to be sure.

[jetadm123]

Re: Sony SMD-HS73

Did you ever verify that you can see an image if you shine a flashlight on the screen? The logic board is getting 5V and the voltage regs are working, therefore, you should at least get an image.

[retiredcaps]

Re: Sony SMD-HS73

This is a low probability, but just for my own curiousity, can you carefully measure the voltage across the main filter capacitor (the big one) and see if you get steady DC voltage?

You are looking for a steady voltage while the screen is flickering. You can use the original ccfls for this test.

For this test, I like to use aligator clips with my multimeter so I can do this measurement without using my hands. It is high voltage that you will be measuring (about 165V DC).

[torin3]

Re: Sony SMD-HS73

Ok I have something for you to try.
Substitute one ccfl at a time again, but find a place on the back of the lcd where you can see the light of the ccfl.As you try the ccfl in each socket dose the brightness look the same on the test ccfl in each socket.
I am hoping this might find a area of the inverter to look at closer.
Al.

When I had all 4 known good CCFLs plugged in, they were all 'bare' and I didn't see any obvious light difference. I will try again.

Can you give us the part numbers for U1, U2 and U3?

/ = new line
U1 = 0Z960S / 0326B1 / V31228.2
U2 = 4542 / (logo)AD(Delta smbol) / W37A
U3 = same as U2

[fuhrer]

Re: Sony SMD-HS73

hi to all ze members.im new here at badcaps.umm we usually encounter that kind of problem.same brand,same model.very hard to find ze culprit. what we do is we replace the inverter with a home made one..it works..but maybe a ten percent degradation in contrast..i

[jetadm123]

Re: Sony SMD-HS73

Can you give us the part numbers for U1, U2 and U3?

[alexanna]

Re: Sony SMD-HS73

Ok I have something for you to try.
Substitute one ccfl at a time again, but find a place on the back of the lcd where you can see the light of the ccfl.As you try the ccfl in each socket dose the brightness look the same on the test ccfl in each socket.
I am hoping this might find a area of the inverter to look at closer.
Al.

[alexanna]

Re: Sony SMD-HS73

Have you done any thing, as far as re soldering the inverter transformers?
Al.
Never mind missed it in an earlier post

[torin3]

Re: Sony SMD-HS73

Sorry, had to use flash, as I don't have bright house lights.

I think I got a clear enough photo. If not, I can try again.

[retiredcaps]

Re: Sony SMD-HS73

Can we get a clear focused close up photo (as close to 2000x2000 and without flash) of the area in red?

edit: What is the part number of that 20 pin IC in the red area?

[torin3]

Re: Sony SMD-HS73

Caps arrived today. Replaced all the cans, including the surface mounted electrolytics.

No change in behavior.

[torin3]

Re: Sony SMD-HS73

Caps should arrive tomorrow.

Well, I guess not.

Looks like Christmas mail slowdown has hit already...