The infamous 2 seconds to black

[EGuevarae]

Re: The infamous 2 seconds to black

T was Taken.

I guess That answers my Question...

[PCBONEZ]

Re: The infamous 2 seconds to black

T was Taken.

[EGuevarae]

Re: The infamous 2 seconds to black

Because T for transformer was already taken?

PlainBill

T in transformer, TH in Thermistor. It could have been TR.
Or, in the case of the C5707, because they fail Quite a lot and are pissing off Quite a big crowd when the Quit working on low Quality designs or implementations? ....MMMMmmmm... I wonder....

[PlainBill]

Re: The infamous 2 seconds to black

Transistors.
R = Resistor
F = Fuse
TH = Thermistor
D = Diode
Q = Transistor <---------------- I don't know why Q, because as you can see we had a pattern here until mr. Q arrived

Because T for transformer was already taken?

PlainBill

[EGuevarae]

Re: The infamous 2 seconds to black

Thanks a bunch eguevarae.
Gonna call it quits for tonight as I have a bunch of CAD homework to do. Will get the monitor put back together on Friday and proceed with the testing.

I'll be waiting.

[shimjocky]

Re: The infamous 2 seconds to black

Thanks a bunch eguevarae.
Gonna call it quits for tonight as I have a bunch of CAD homework to do. Will get the monitor put back together on Friday and proceed with the testing.

[EGuevarae]

Re: The infamous 2 seconds to black

before we go any further I have another silly question for ya. Is it ok to do all this on the bench? That is to say will the power supply work properly without being hooked up to everything?

Not silly. That is a good question. Some PSUs work on the bench and others need load to work. If it makes you more comfortable, you can hook it up to the rest of the monitor and test. The lamps would not come on until the inverter receives the BL_ON signal, that comes from the Video board. Hook it all together, and see what happens. With the monitor in the ON state, and with signal applied (green led on the front, with VGA cable connected), redo the reads on the jumpers.
Asking is the way you'll learn, so don't be afraid. Nobody sees you, actually (except maybe the more than 10,000 members, but we don't count ...)

[shimjocky]

Re: The infamous 2 seconds to black

before we go any further I have another silly question for ya. Is it ok to do all this on the bench? That is to say will the power supply work properly without being hooked up to everything?

[EGuevarae]

Re: The infamous 2 seconds to black

I checked both jumpers and both sides of the cap. In all cases i get a spike to less than 1 volt then it drops off to 0.

I've run out of ideas for now. The voltage that reaches teh inverter area is 12v or more, depending on the number of lamps (I've seen 12,13 & 14 v so far). Check the voltage in the 12 V rail caps (those with 16 or 25v ratings) that you changed. You mentioned that the 12V line fluctuated before. What readings have you now on the 12v line?
Also, what V do you read on the resistor between the Schottky and a cap?
at the left):

Double check for correct orientation of caps and make sure the solder is OK (reflow if necessary). We'll be dealing only with the 12v line only, i guess.

[shimjocky]

Re: The infamous 2 seconds to black

I checked both jumpers and both sides of the cap. In all cases i get a spike to less than 1 volt then it drops off to 0.

[EGuevarae]

Re: The infamous 2 seconds to black

I can read one Q.
The top line says LT7215H.
The second says SBL1060CT.

The other one has absolutely no markings. Could they have been destroyed by heat?I will have to learn up on where to probe them for voltage.

I assume to test the transformer that all the outputs are + ? So if I probe any of the wires coming out of it and ground I should be good to go, yes?

P.S. Thanks for taking the time to explain basic things. I am sure that must get old for those who are experienced.

Nevermind the explanation.I can explain anything you want or need, even if you think it is a 101 sort of thing. I learned that way, and I can pass that on to the newcomers. Sometimes I post comments or explanations along my posts so people that just browses around and never register to make any question directly, can benefit from the forum.
I am not that wise as PCBONEZ, Krankshaft, Wizard and many others around here (Toasty has been a great help too), but if in any form I can help, I will.

Now, back to our patient ....

The component is a Schottky Barrier (see here ).
Nevermind the T for now. Look at the picture. Do you have voltage reading in any of those two jumpers, and on the cap in the picture?

[shimjocky]

Re: The infamous 2 seconds to black

I can read one Q.
The top line says LT7215H.
The second says SBL1060CT.

The other one has absolutely no markings. Could they have been destroyed by heat?I will have to learn up on where to probe them for voltage.

I assume to test the transformer that all the outputs are + ? So if I probe any of the wires coming out of it and ground I should be good to go, yes?

P.S. Thanks for taking the time to explain basic things. I am sure that must get old for those who are experienced.

[EGuevarae]

Re: The infamous 2 seconds to black

Cant seem to get the same results with my psu tester as I did last time, not sure why, maybe my tester is broke. I am checking voltage at the output to the vid board and its showing good there but then it did before too.

I wouldnt know a fuse on the bottom if it bit me in the ass,lol. I did look at your latest pic in the westinghouse thread and made the assumption that a small fuse would be labeled with an F, if so I found none.

Q's???

Transistors.
R = Resistor
F = Fuse
TH = Thermistor
D = Diode
Q = Transistor <---------------- I don't know why Q, because as you can see we had a pattern here until mr. Q arrived

If you can post the number on them (and if you can read voltage on them). And you are right. F is what you'll be looking for. I found none, either on the top side or the bottom.
Do you have voltage reaching the transformer ("T")?

[shimjocky]

Re: The infamous 2 seconds to black

Cant seem to get the same results with my psu tester as I did last time, not sure why, maybe my tester is broke. I am checking voltage at the output to the vid board and its showing good there but then it did before too.

I wouldnt know a fuse on the bottom if it bit me in the ass,lol. I did look at your latest pic in the westinghouse thread and made the assumption that a small fuse would be labeled with an F, if so I found none.

Q's???

[EGuevarae]

Re: The infamous 2 seconds to black

After doing some reading here I decided to do what I could to troubleshoot the power supply. I was able to bench test it and with my multimeter I found that it was putting out the proper +12V and +5.2V. I then rigged it into my psu tester to try and put it under a load. What I found was that when I did this the +12V dropped to about 10.7V while the 5.2 stayed strong.

Could the voltage drop under load possibly be why this monitor fires up then fails?.

Did you re test it after the recap?

[EGuevarae]

Re: The infamous 2 seconds to black

See the marked components? those are jumpers. There may be a fuse around that area, as I can't locate any on the other side of the board.

What are the markings/part number on those two Q's?

Do you have any voltage reading AFTER the caps (like in the inverter's transformer)?

[shimjocky]

Re: The infamous 2 seconds to black

Here is my latest round of pics. Still can't seem to upload to the forums here even though they are within the rules for size, keep getting database errors,ugh.

Took several pics of both sides with no flash so hopefully they will be helpful.

[EGuevarae]

Re: The infamous 2 seconds to black

Repost a clearer picture of the underside of the board to see if there's a SMD fuse to check. It was a problem with two Westinghouse units that have been discussed recently.

[shimjocky]

Re: The infamous 2 seconds to black

Back again.

I got my caps today and did the power supply/inverter. I fired it up and I have the same problem as before. Well, actually the problem is worse now.

At one point before recapping I reassembled the monitor to do the flashlight test. I could see the faint pic so I know that part is working. Problem is that instead of the backlights coming on for a couple seconds they did not come on at all. The symptom is still the same after recapping.

I decided to tear it down further to look at the lamps. Boy I almost wish I hadn't! These things are a mess to take apart and I just hope I can remember how to get it back together again.

Anyhoo, since I have it apart what can I do to check the lamps? I honestly don't know what to look for. Also, is there a way I can test the inverter side of the power supply?

Thanks again for the advice thus far. I am learning a lot and having fun doing the work so keep it comin!

[sofTest]

Re: The infamous 2 seconds to black

When I'm ordering from DigiKey, I always order Panasonic FMs if the value I need is available in that series. They are better spec, and sometimes they are also cheaper than FC.