Sony SDM-HS75P

[Joun]

Hello everyone..
I have this Sony SDM-HS75P monitor that doesn't power at all.
No lights,nothing ..I thought that it got some diodes shorted and it burn its fuse but everything seems to be OK.Voltage on primare cap measures fine generally the primary side looks good.
On the output voltage connector I measure 12volts and 5volts,but: I have a strange voltage of 1.5 volts that doesn't look good..Do you think that this is the problem and can that prevent it from powering on or do I have to look at the vga board?

Thank you.

[retiredcaps]

Re: Sony SDM-HS75P

or do I have to look at the vga board?

If you have no power led, then you have to look at the vga board. Post pictures. There may be some voltage regulators and one or more of them may have gone bad?

[Joun]

Re: Sony SDM-HS75P

Thank you for your answer..
I will post pictures tomorrow, I just want to ask you about that 1.5 volt on the connector, is that normal?
Yes there are two regulators, I'll check them.

[retiredcaps]

Re: Sony SDM-HS75P

I just want to ask you about that 1.5 volt on the connector, is that normal?

On some power boards there is a legend that lists all the expected voltages. Sometimes it is on the front, other times it is on the back.

If there is no legend, then 1.5V could be normal as there are many functions like brightness control, dimming, etc that use lower voltages.

5V is usually standby. 12V is probably for the inverter section.

[Joun]

Re: Sony SDM-HS75P

The truth is that nothing seems strange or burned..So I guess power supply is fine.
I will check the regulators on VGA board and post pictures.

[selldoor]

Re: Sony SDM-HS75P

Hi- Looks like someone has had a go at this board? I have marked soldering areas in yellow which might need re -visiting.The Big cap especially looks poor.
The component at U802( Marked in red) looks to be melted? is that just my eyesight?
The area marked in violet looks like a solder bridge but appears cracked?
If it is meant to bridge it needs redoing. If its not it needs undoing.

Id have thought the 1.5 volts should be 3.3 but cant find much out about this board.
it is a 715G1447-1-GP
The Big Cap is a UCC are the others the same manufacturer?.
The vga board may be a different manufacturer what are the caps on that. You should post a picture - may help others in future and explain the 1.5v.

There is also a thread on a polish site which appears to have the same symptoms someone has suggested U202 may be faulty but I cant see a U202 on the board? can you see one or is on the vga?
http://translate.google.com/translat...3.html&act=url

[Joun]

Re: Sony SDM-HS75P

Hello,thank you for your answer.
Component U802 looks melted,but it isn't.It is just flux on it.Same goes for primary cap..It has lot of flux on solder(not from me), I try to redo soldering points on it.
Exactly the same goes for the two diodes you marked with yellow.I have desolder them for measuring and didn't clean paste at all.
All in all it doesn't look like someone has messed with it before..

P.S Thanks for the polish link!

[Joun]

Re: Sony SDM-HS75P

Here are the VGA board pictures..Regulators looks and measures just fine, 3.3Volts and 1.8Volts as they should.Measure voltages at the connector that goes to button board and see there are 12 and 5 volts present.

Any ideas?

P.S I didn't want to use flash so photos are uneven lighted.Everythink on boards are optically OK.

[retiredcaps]

Re: Sony SDM-HS75P

Any ideas?

Can you indicate on the logic board which pin is 1.5V DC?

Can you also mark up the logic board picture to show the DC voltages from the power board on the different color connectors?

[Joun]

Re: Sony SDM-HS75P

There you are..
I was wrong about the 1.5V voltage..There isn't any.

[retiredcaps]

Re: Sony SDM-HS75P

Okay, without a schematic or some legend, I can't tell which of the pins that read 0.0V is the PS_ON pin.

Some will read 0.0V because it is ground. You can do a quick resistance check with respect to ground to see which read less than 1.0 ohms. Those that do are likely to be ground. Those that are left might be PS_ON.

What I'm about to suggest might damage your monitor so you have to decide for yourself.

Disconnect the main board from the power board.

For those pins that are left at 0.0VDC try hooking up 2 AA cells in series to get 3.0V DC. Apply 3.0V DC to the unknown pins and see if the backlight comes on. If it does, then you have found PS_ON.

From there, it is a matter of tracing PS_ON on the logic board to see why there is no 3.? V DC.

[Joun]

Re: Sony SDM-HS75P

Nice trick! Will do so when I get back.. Just a question: The upper connector goes to button board and has lots of 3.3V voltages.
Is that irrelevant?
Thank you.

[retiredcaps]

Re: Sony SDM-HS75P

The upper connector goes to button board and has lots of 3.3V voltages.
Is that irrelevant?

I can't see the top of the picture, but I assumed (maybe incorrectly) that cable went to the front keyboard.

The lower connector is the only one to the power board so PS_ON has to be here.

The other way to force the backlight on is to tie a resistor between 5V standby and PS_ON as tom66 and PlainBill have mentioned a few times here.

https://www.badcaps.net/forum/showpo...9&postcount=45

[Joun]

Re: Sony SDM-HS75P

I can't see the top of the picture, but I assumed (maybe incorrectly) that cable went to the front keyboard.

Yes,that's right.You can see it in the pictures I have posted earlier(post #8 )..
I will try the resistor trick,thank you very much!

[Joun]

Re: Sony SDM-HS75P

Well resistor trick worked just fine..
PS_ON pin is the brown one( at the bottom left of the connector )
I removed the connector from VGA board and place the resistor between this pin and the white one that has 4.88volts.The thing is that the backlight lit ,but brown pin had too high voltage about 4.6Volts( maybe was drawing less current that expected? )
With a little try and era found that it needed 33K resistor to drop voltage at 3.2volts.Now the backlight is lighting..
What does that mean?

[selldoor]

Re: Sony SDM-HS75P

Hi just changed my"Status" from senior member to slow learner as senior member may suggest I know what im talking about.

As Retired caps said "From there, it is a matter of tracing PS_ON on the logic board to see why there is no 3.? V DC."

As a suggestion this may get us back to the Polish Page and my question re U202. On logic board back is U202 the one in the top left hand corner.
I think it may be labelled as 74 LVC14AB. 60450D If so, the data sheet is attached and perhaps someone can suggest how to test it?

[PlainBill]

Re: Sony SDM-HS75P

Hi just changed my"Status" from senior member to slow learner as senior member may suggest I know what im talking about.

As Retired caps said "From there, it is a matter of tracing PS_ON on the logic board to see why there is no 3.? V DC."

As a suggestion this may get us back to the Polish Page and my question re U202. On logic board back is U202 the one in the top left hand corner.
I think it may be labelled as 74 LVC14AB. 60450D If so, the data sheet is attached and perhaps someone can suggest how to test it?

It's easy. It's a 14 pin IC, pin 7 is Gnd, pin 14 is power. Pins 1, 3, 5, 9, 11, and 13 are inputs. Pins 2, 4, 6, 8, 10, and 12 are outputs. The association is 1 - 2, 3 - 4, .... 13 - 12. And it's an inverter - if pin 1 is high, 2 should be low.

Now my question to you is: If pin 1 is low (0volts) and pin 14 is 5 volts, what voltage should you see on pin 2?

PlainBill

[Joun]

Re: Sony SDM-HS75P

Now my question to you is: If pin 1 is low (0volts) and pin 14 is 5 volts, what voltage should you see on pin 2?

PlainBill

Well I didn't quite understand that:You're asking to see what my knowledges are,or you asking to check voltages and post results?
I'm saying that because you wrote "should you see" not "do you see" on your post..

[retiredcaps]

Re: Sony SDM-HS75P

Well I didn't quite understand that:You're asking to see what my knowledges are,or you asking to check voltages and post results?
I'm saying that because you wrote "should you see" not "do you see" on your post..

It is a quiz to see if you understand what he wrote. I have seen him ask others as well.

You can verify your answer by measuring the IC.

[Joun]

Re: Sony SDM-HS75P

Well I am an electrical engineer, I don't have to verify my answer( I mean,I'm sure about it) ..I even can't measure the IC since I'm away now.
Since it is an inverter, pin 2 must have the opposite state of pin 1, if pin 1 is 0volts pin 2 is 5volts..