Starlogic HD20W

[bsweasel]

I have a Starlogic HD20W LCD that has the infamous 2 seconds to black problem. I've been reading up on this and would like to test the inverter coils, but I can't find any specs on these things. So I thought I'd as for some help. Here are some pics(sry poor quality) Will do better ones later. And the inverters have the following printed on the side.
LTL19009607B
HI-POT BJ0630

Can anyone help with the pinout or what I should expect for ohm readings?

[bsweasel]

Re: Starlogic HD20W

I know others may ask this: Controller chip is 16 pin:
UTC TCA5
TL494L

http://pdf1.alldatasheet.com/datashe...94L-S16-T.html

[retiredcaps]

Re: Starlogic HD20W

I like this video on how to test a transformer.

http://www.youtube.com/watch?v=eNuGWBPRGKA

You may not need to know the specs if the transformers are both identical in readings.

Also, test your voltage regulators on the inverter board.

I've been reading up on this and would like to test the inverter coils, but I can't find any specs on these things.

[bsweasel]

Re: Starlogic HD20W

I like this video on how to test a transformer.

http://www.youtube.com/watch?v=eNuGWBPRGKA

You may not need to know the specs if the transformers are both identical in readings.

Also, test your voltage regulators on the inverter board.

I watched that video.....problem is I don't know what pins are primary/secondary so I'm not sure I'm checking the right things.
Second...could you point out the voltage regulators to me....I'm still learning what all this stuff looks like!

[retiredcaps]

Re: Starlogic HD20W

Also, check the fuses on the inverter board to make sure none are open.

AFAIK, another test you can do for transformers is (with power off and unplugged) with ohms setting is described below. It doesn't matter which you pick as pin 1. What you are looking for is that they are the same on both transformers.

pin 1 to 2, 1 to 3, 1 to 4, etc 1 to last pin
pin 2 to 3, 2 to 4, etc
pin last pin-1 to last pin

write down the ohms reading for each. What you are looking for something that is obviously out of place. For example, if transformer #1 pin 2 to pin 4 is 0.5 ohms and transformer #2 (same pins) is 5000 ohm, then you know something is wrong.

Voltage regulators are circled in red.

As for learning, I am hoping I am explaining things correctly. I'm learning by following PlainBill's/Wizard and other's posts.

PS. Check the transistors on the power board to make sure none are shorted. On the Benq power boards, the C5707s are often shorted.

I watched that video.....problem is I don't know what pins are primary/secondary so I'm not sure I'm checking the right things.
Second...could you point out the voltage regulators to me....I'm still learning what all this stuff looks like!

[retiredcaps]

Re: Starlogic HD20W

Just for completness sake and because the problem may not be in the inverter board, post clear focused pictures of the logic and power board - both sides (top down view).

Take the boards to a window on a sunny day and use macro mode for best quality pics.

2 seconds to black could be a problem on any of the boards (power, logic, or inverter). Or bad CCFLs, or solder joints.

Here are some pics(sry poor quality) Will do better ones later.

[bsweasel]

Re: Starlogic HD20W

Ok new HQ pics posted. This 2 seconds to black thing is really driving me crazy.

[PlainBill]

Re: Starlogic HD20W

What is the part number of U101 (the 16 pin IC on the inverter)?

PlainBill

[bsweasel]

Re: Starlogic HD20W

I know others may ask this: Controller chip is 16 pin:
UTC TCA5
TL494L

http://pdf1.alldatasheet.com/datashe...94L-S16-T.html

Plainbill, U101 was above....I was right, I knew someone would ask. I just don't know how to test it after reading that datasheet.

[retiredcaps]

Re: Starlogic HD20W

I just don't know how to test it after reading that datasheet.

I believe the proper way to test is to look at page 2 for the pinouts.

Pin 7 is GND so your black lead/probe goes here. Then your red lead/probe goes to the other pins and you measure the DC voltage and compare them within the specified ranges on page 3-4.

Of course a schematic with the "known good" voltages would be more helpful, but at least you get an idea of the range. For example, if you measure 2V DC and the value on Vref is supposed to be 5V DC, then you can search what is causing this low voltage.

[PlainBill]

Re: Starlogic HD20W

Plainbill, U101 was above....I was right, I knew someone would ask. I just don't know how to test it after reading that datasheet.

This is going to be a real PITA to test using the usual techniques - actually, using ANY techniques. U101 is a general purpose SMPS controller, not a dedicated backlight controller. I'm pretty sure the IC itself is good, it's a question of why it's shutting the backlights off.

Possible causes are:

1. Low or no output from one transformer.

2. One of more CCFL (or the wiring to it) is bad.

3. A component in the sense circuitry is bad.

The logical way to tackle this is to use a known good CCFL as a substitute for each of the ones in the panel, in turn. If the inverter stays on only when the test CCFL is used to replace one particular tube in the monitor, we know the problem is that CCFL or the wiring.

If the test CCFL does not work when it replaces one particular tube, we know the problem is that output.

If nothing can change the 'two seconds to black', we know it's the sense circuitry.

PlainBill

[bsweasel]

Re: Starlogic HD20W

I don't have any ccfls with 4 wires in a dual plug...it appears that the 2 thicker wires are on one side of the connector and the 2 returns are on the other....is that common to split the hot and returns into a 4 wire connector? I did substitute a ccfl with a single connector 2 wire config into the 2 connects that had such and it didn't make a difference.

Will the transformers give the correct outputs without the CCFL's attached after it goes black? or do I have to power it on while holding probes to the CCFL outputs to read the output voltage.

[PlainBill]

Re: Starlogic HD20W

I don't have any ccfls with 4 wires in a dual plug...it appears that the 2 thicker wires are on one side of the connector and the 2 returns are on the other....is that common to split the hot and returns into a 4 wire connector? I did substitute a ccfl with a single connector 2 wire config into the 2 connects that had such and it didn't make a difference.

Will the transformers give the correct outputs without the CCFL's attached after it goes black? or do I have to power it on while holding probes to the CCFL outputs to read the output voltage.

I personally wouldn't try to measure the voltage out of an inverter transformer with a standard DMM. I know people have tried it, but the voltage is at the limit of or above the maximum voltage specified for most DMMs.

There is a safe way to do this, however. Make these readings while the CCFLS are on.

Starting at the left end of the inverter, one end of C126 is tied to T102. The other end is tied to D122 and C148. C126 and C148 form a voltage divider. D122 rectifies that; measure the DC voltage between the two 'bottom' legs of D122.

Moving to T101, C125, C147, and D121 perform the same function. This time, measure the voltage between the two legs on the right side of D121.

And last, T100, C124, C146, and the bottom legs of D120.

PlainBill

[bsweasel]

Re: Starlogic HD20W

Starting at the left end of the inverter, one end of C126 is tied to T102. The other end is tied to D122 and C148. C126 and C148 form a voltage divider. D122 rectifies that; measure the DC voltage between the two 'bottom' legs of D122.

Moving to T101, C125, C147, and D121 perform the same function. This time, measure the voltage between the two legs on the right side of D121.

And last, T100, C124, C146, and the bottom legs of D120.

PlainBill

Sorry for the delay, been busy.... Here are the results.

D122 = 0.6v
D121 = 0.5v
D120 = 1.7v

I used a surge bar on the floor for a foot activated power switch. Put my leads on the pins and turned it on to get these reading. They only read for a second then go to zero. Also during this test I could hear a little buz sound at startup. I also did NOT have a video signal going to the monitor...not sure if that makes a difference?

[PlainBill]

Re: Starlogic HD20W

Sorry for the delay, been busy.... Here are the results.

D122 = 0.6v
D121 = 0.5v
D120 = 1.7v

I used a surge bar on the floor for a foot activated power switch. Put my leads on the pins and turned it on to get these reading. They only read for a second then go to zero. Also during this test I could hear a little buz sound at startup. I also did NOT have a video signal going to the monitor...not sure if that makes a difference?

Good job. Here's a very quick rundown on what is going on. The output voltage from T100 goes through L100 and then to two of the CCFLs. C124 and C146 are in series and form a capacitive voltage divider. While it is physically smaller, C146 has a much greater capacitance than C124. That means the majority of the voltage is dropped across C124. Under normal operation there should be a very small voltage across the two bottom pins of D120. If a lamp is broken, a wire disconnected or broken, etc the voltage across the output of T100 will rise, the voltage across the bottom pins of D120 will rise, shutting down the inverter. This is referred to as either Open Lamp Detection, Over Voltage Protection, or some variation of that. Of course, the same arrangement exists on the other transformers.

Now we have to figure out WHY this is happening. One possibility is an open lamp. Another is the output from T100 is not reaching one (or both) of the lamps connected to it. A third possibility is C124 has increased in value, or is leaky. A fourth is that C146 has decreased in value.

Let's take this a step at a time. Start with the output of T102 (it's the trace covered in white, also the one going to C126). It should go to 1 pin on a connector on each end of the board. Do the same for T101 and T100. If you can establish continuity to two connector pins for each transformer, we will pursue the other possibilities.

PlainBill

[bsweasel]

Re: Starlogic HD20W

T102 has continuity to the top 2 pins of CN103
T101 has continuity to top pin of CN104 and bottom pin of CN102.
T100 has continuity to bottom 2 pins of CN101

So next I guess we test C124 and C146?

C146 I can't see any markings on it......

C124 is:
C
18J
3kv
jnc

This is going to be tricky I'm ill equiped to test these I think ...no CCFL's with the right connectors.....and no ESR meter to test caps....I'm in trouble!!

[bsweasel]

Re: Starlogic HD20W

could I switch the CCFL's from one side to the other and repeat the test on D120 and D122? If its the lamps won't D122 react the same as D120?

EDIT: I did switch CCFL and D122 now is 1.7v.....so I'm looking at bad wires or bad lamps it appears.

[bsweasel]

Re: Starlogic HD20W

I'm thinking that either the lamp on the pink or blue wire, or both are bad. Since they are on the double connector and this is the one that is giving me troubles. Has anyone seen a 3 lamp setup like this, and can I take out one/two, or do I have to buy all three in a "kit" like this one?

[bsweasel]

Re: Starlogic HD20W

I'm thinking that either the lamp on the pink or blue wire, or both are bad. Since they are on the double connector and this is the one that is giving me troubles. Has anyone seen a 3 lamp setup like this, and can I take out one/two, or do I have to buy all three in a "kit" like this one?

I'm just going to keep answering my own questions. It appears that I will be disassembling this, ordering new ccfl and soldering it to the wires. Upon removing them and inspecting during turn on. The middle ccfl with the blue wire is the one that is not lighting up fully as compared to the other five ccfls.

[bsweasel]

Re: Starlogic HD20W

Got my new CCFL today. Replaced the center CCFL, and its the same symtoms....2 seconds to black....and after a few times of off and on with the power supply now its about 1/2 second to black. Maybe both lamps on that section of the inverter?

D122 which is the section where the replacement lamp is, is still measuring 1.3-1.6 volts during the brief flash of the lamps.....

Plainbill, you have any more insights? This is driving me nuts!! If I get this fixed I'm going to throw a celebration party to regrow some of my hair!!!