Sony SDM-HS93, flashing display

[Freezer]

My latest project is a Sony SDM-HS93, 19" LCD monitor with CCFL backlights. The person who gave it to me said the monitor would "flash." Before I even turned it on, I opened it up (which was pretty easy since Sony used screws on this monitor instead of the plastic clips which can be a pain to open).

The monitor has the standard layout with the power/inverter board on the left and the video board on the right. There were no bulding capacitors, however one of the caps (C112) had leaked electrolyte out the top, down the side and onto the PCB (see picture). Given this I decided to replace all the caps on the power/inverter board except the big fat one. At the same time, there was a single cap (C840) on the video board with a slightly high ESR. It wasn't really high (.3 versus .03 for the replacement cap), but I decided to replace it as well.

After replacing all the caps I powered on the monitor only to discover that it was still flashing. The flashing is slow and random. The monitor will stay on for 1 - 3 seconds, then stay off for 1-3 seconds. It continues this pattern over and over.

There is a single cable between the power/inverter and the video boards (labeled CN5). The 11 wires are labeled as such:

1. 12V
2. 12V
3. Ground
4. Ground
5. 5V
6. 5V
7. Ground
8. 5V
9. On/Off
10. Dimming
11. Dimming

I've noticed when the monitor is flashing that wire 9 (on/off) switches from 0 to 5V. So my theory is the power/inverter board is functioning properly and the video board is telling the power/inverter board to turn on and off. To test my theory I jumped the 5V standby to the on/off pin. When I did this the backlights came on and stayed on. So I'm pretty sure the problem is on the video board. But I'm not sure what to check next. Any suggestions? Thanks.

[Toasty]

Re: Sony SDM-HS93, flashing display

CCFL's

[Freezer]

Re: Sony SDM-HS93, flashing display

CCFL's

Are you suggesting the CCFLs themselves are bad? I'm not so sure about that. As I said, if I connect the On/Off pin to a 5V source, the backlights come on and stay on. Wouldn't bad CCFLs refuse to turn on and stay on?

Actually now that I think about it, I tried the flashlight test while the monitor was flashing. When the backlights were off, there was no video on the screen. This tells me the video card is A) turning off the backlights and B) cutting the video signal to the LVDS cable.

I do have some spare CCFLs at home that I could try. They don't have the same connector as this monitor so I'll have to rewire it. But I guess it's worth a try.

[Toasty]

Re: Sony SDM-HS93, flashing display

You did say you did all the electrolytic caps on the PSU and the 2 out in the Inverter.
All low ESR caps? No Radio Shack garbage.

How about the large one on the Video and testing of the 7 little SM ones?

Forcing the "on" which is normally switched from the video, yes? Bad voltage regulator? Monitor the on voltage when working between flashes. 5v?

Wait for PlainBill to pop in. He handles more of these than I.

A monitor that is 6 or 7 years old, yes? That's why I suspect CCFL's right after the caps are done.

.

[alexanna]

Re: Sony SDM-HS93, flashing display

Can you check and see if any of the U components on the logic board are voltage regulators.
If we're lucky part or the number stamped on them with there output voltage.
You also may want to power on the monitor with everything hooked up including a signal, With the exception of the ribbon cables going to the panel, dose anything change?.
Also what is the front PLED doing when the back lamps are flashing?

[PlainBill]

Re: Sony SDM-HS93, flashing display

CCFL's

No. Read the description. The inverter control line is switching the CCFLs on and off. Note the pinout of the cable - there is no signal from the inverter to the signal board to tell it the CCFLs had gone off. When he forced the Inverter control line on, the CCFLS stayed on.

PlainBill

[PlainBill]

Re: Sony SDM-HS93, flashing display

What are the part numbers of U801 and U803? Those appear to be voltage regulators, and MIGHT be the cause of the problem.

PlainBill

[Freezer]

Re: Sony SDM-HS93, flashing display

Thanks for all the replies. Toasty - to answer your question I used all low ESR caps. Specifically Panasonic FM series (and a couple of FC series where FM wasn't an option). This doesn't really matter since I'm like 99% sure the problem is over on the video board.

PlainBill, here's the answer to your question:

U803 - First line = D31AB, second line = 1026025 (it might be 1026D25, hard to read).
U801 - First line = BA033, second line = 32 33.

I can't find datasheets for either of these. Assuming those are voltage regulators, I probed the pins while the monitor was in a flashing state. For the most part the voltages were steady. One pin of U803 fluctuated between 4.4 and 4.6 volts. If these were the cause of the problem, I would expect a fluctuation in the range of 0 - 5 volts. A .2 volt variance couldn't be the source of the problem, right?

I leave for vacation in a few days, so I might have to put this project on hold. In the meantime, any suggestions/questions posted here - I'll look into them as soon as I get back. Thanks.

[PlainBill]

Re: Sony SDM-HS93, flashing display

Thanks for all the replies. Toasty - to answer your question I used all low ESR caps. Specifically Panasonic FM series (and a couple of FC series where FM wasn't an option). This doesn't really matter since I'm like 99% sure the problem is over on the video board.

PlainBill, here's the answer to your question:

U803 - First line = D31AB, second line = 1026025 (it might be 1026D25, hard to read).
U801 - First line = BA033, second line = 32 33.

I can't find datasheets for either of these. Assuming those are voltage regulators, I probed the pins while the monitor was in a flashing state. For the most part the voltages were steady. One pin of U803 fluctuated between 4.4 and 4.6 volts. If these were the cause of the problem, I would expect a fluctuation in the range of 0 - 5 volts. A .2 volt variance couldn't be the source of the problem, right?

I leave for vacation in a few days, so I might have to put this project on hold. In the meantime, any suggestions/questions posted here - I'll look into them as soon as I get back. Thanks.

If those are voltage regulators, any fluctuation signals trouble. For one thing, it could be tripping a reset line.

I've marked up the picture, and have a few questions.

1. What are the voltages on the points marked 1, 2, and 3 on U801?

2. What are the voltages on the points marked 1, 2, and 3 on U803?

3. What is the part number of U804?

4. I can't find U802. Can you?

Enjoy your vacation. Remember that the work will still be waiting when you get back.

PlainBill

[Freezer]

Re: Sony SDM-HS93, flashing display

The part number on component U804 is 65BAG.

Here are the voltage readings you requested. I took them while the monitor was on in it's flashing state.

U801
Pin1: 4.94V
Pin2: 3.33V
Pin3: 0V

U803
Pin1: 0V
Pin2: 4.48V - 4.67V
Pin3: 2.49V

I have searched this PCB top and bottom, I do not see U802 anywhere. It must not exist.

Brian

[PlainBill]

Re: Sony SDM-HS93, flashing display

The part number on component U804 is 65BAG.

Here are the voltage readings you requested. I took them while the monitor was on in it's flashing state.

U801
Pin1: 4.94V
Pin2: 3.33V
Pin3: 0V

U803
Pin1: 0V
Pin2: 4.48V - 4.67V
Pin3: 2.49V

I have searched this PCB top and bottom, I do not see U802 anywhere. It must not exist.

Brian

It would be interesting to know why the voltage on the input of U803 varies so much. Still, that's not likely to be the problem It's obvious these are the I/O (3.3V) and core (2.5V) regulators for the Gemini chip.

PlainBill

[Toasty]

Re: Sony SDM-HS93, flashing display

>>No. Read the description. The inverter control line is switching the CCFLs on and off. Note the pinout of the cable - there is no signal from the inverter to the signal board to tell it the CCFLs had gone off. When he forced the Inverter control line on, the CCFLS stayed on. <<

Sorry, I nodded off after the 2nd paragraph...

When you jump the on/off, is that done by itself, or when you power it on?
Does the video then continue to disappear/flash even though you've jumpered the backlights on.

Again-
How about the large one on the Video and testing of the 7 little SM ones?

And for Alexanna-
Also what is the front PLED doing when the back lamps are flashing?

T