Sony SMD-HS73

[torin3]

Monitor powers on, display turns on, then off, then flickering like auto-adusting, then on for a few seconds, then more flickering, then off, then on, but with the display at the wrong resolution, then off, then flickering, etc...

It would settle down and the display stay on after it had warmed up for a few minutes. It no longer seems to settle down.

No visibly bad caps, and I don't have an ESR meter.

I haven't tried a good CCFL yet. I did see another post where someone fixed this model by replacing Q207 that had gone high on ESR. Q207 is a 10uf 16V surface mount cap. It is the small cap next to the brown sleeved smaller electrolytic on the logic board.

I did touch up the solder connections on the transformers.

[jetadm123]

Re: Sony SMD-HS73

Don't you mean C207? The designator "Q" usually specifies a transistor. Your description sounds like a cap problem. If you think that replacing the 10uf cap will solve the problem, give it a try. You can use a regular low-esr electrolytic cap in place of the surface mount one. Using a pair of pliers, bend the leads outward. If you have an old computer power supply, you might be able to "liberate" a 10uf for testing purposes.

Also, what's the brand/series of caps on the power board? Note: Caps don't have to buldge to be bad.

[torin3]

Re: Sony SMD-HS73

Don't you mean C207?

Yes, typo/thinko as I was getting ready to head out the door.

Your description sounds like a cap problem. If you think that replacing the 10uf cap will solve the problem, give it a try. You can use a regular low-esr electrolytic cap in place of the surface mount one. Using a pair of pliers, bend the leads outward. If you have an old computer power supply, you might be able to "liberate" a 10uf for testing purposes.

I have several new 10uf 50V eletrolytics (Panasonic) that I could use to try. If I remember right, you can go over on the voltage spec, right?

Also, what's the brand/series of caps on the power board? Note: Caps don't have to buldge to be bad.

Most are Rubycon YXG, though there are 2 Sam Young LXZ caps on it as well.

And yes, I'm aware they don't have to bulge to be bad.

[retiredcaps]

Re: Sony SMD-HS73

If I remember right, you can go over on the voltage spec, right?

Yes, but 50V is likely overkill for any cap on the logic board. Most logic boards I have seen only require 5V or less. The exception is the last monitor I have tried to repair. It had 19V DC on the power board connector going to the logic board.

[jetadm123]

Re: Sony SMD-HS73

I have several new 10uf 50V eletrolytics (Panasonic) that I could use to try. If I remember right, you can go over on the voltage spec, right?

Yes, you can use a higher voltage.



If the cap doesn't solve your problem, you might consider the following:

1) replace all the small electrolytic caps on the power board with better quality ones.

2) measure the output voltages to make sure you're getting a clean 5V and 12V output.

3) Measure the voltage regulator(s) output on the logic card.

4) possible bad inverter transformer or CCFL tube(s).

[torin3]

Re: Sony SMD-HS73

Yes, you can use a higher voltage.



If the cap doesn't solve your problem, you might consider the following:

1) replace all the small electrolytic caps on the power board with better quality ones.

I replaced:
3x 470uf, 25V
1x 1000uf, 25V
1x 1000uf, 16V

I wasn't able to swap out a 100uf, 35V and a 1uf, 10V that I didn't have replacements for.

2) measure the output voltages to make sure you're getting a clean 5V and 12V output.

3) Measure the voltage regulator(s) output on the logic card.

4) possible bad inverter transformer or CCFL tube(s).

I tried checking T1 and T2. I think they are ok. Secondaries are about 1K ohm. And I get identical restances for the two units.

I also tried 1 lamp from another montior, in each of the sockets.

Still no change in behavior.

[retiredcaps]

Re: Sony SMD-HS73

What about question 2? Stable voltages for 5V and 12V DC?

[jetadm123]

Re: Sony SMD-HS73

The 1uf is probably part of the startup circuit and if bad, can cause power up problems.

Check voltage reg(s) output. I circled in the photo what I think are the regs. I can't see the part numbers. If they are marked 1117, then they are regs. The number 18 or 33 will indicate a 1.8V or 3.3V output.

[torin3]

Re: Sony SMD-HS73

What about question 2? Stable voltages for 5V and 12V DC?

Sorry, I was starting to fall asleep, so I cut it short for th evening.

12V = 13.82V
5V = 5.05V

The 1uf is probably part of the startup circuit and if bad, can cause power up problems.

Check voltage reg(s) output. I circled in the photo what I think are the regs. I can't see the part numbers. If they are marked 1117, then they are regs. The number 18 or 33 will indicate a 1.8V or 3.3V output.

The one on the right is marked BA033 (second line) 37 15. I think it is this is the data sheet for it, even though I can't see a T at the end:
http://www.alldatasheet.com/datashee...HM/BA033T.html

3.36V output.

The one on the left is marked D 35 AG (second line) 1086D25. I think this is the data sheet for it: http://www.ic-on-line.cn/IOL/viewpdf...25_2827670.htm

2.48V output.

I guess I'll order in the rest of the caps and replace them. Should I order the surface mount ones for the logic board too. Also there is a 470uf 25V cap on the logic board I can replace as well.

Looks like it is well past the time to get a Bob Park kit and make it up so I can have an ESR meter.

[retiredcaps]

Re: Sony SMD-HS73

12V = 13.82V
5V = 5.05V

The legend on CN1 in the photo is a bit obscured, but if it says 12V, then 13.82V is pretty high? Was this measured with all the boards (logic and ccfl) hooked up?

I believe the 12V DC is for the inverter section.

[torin3]

Re: Sony SMD-HS73

The legend on CN1 in the photo is a bit obscured, but if it says 12V, then 13.82V is pretty high? Was this measured with all the boards (logic and ccfl) hooked up?

I believe the 12V DC is for the inverter section.

CN1 legend:
+12V
+12V
GND
GND
+5V
+5V
GND
N/C
ON/OFF
Dimming
N/C

And yes, almost 14V out of a 12V line seems like it would be out of spec to me too. But I'm not sure where to look for what might be affecting it.

Yes, all boards and lights hooked up. VGA cable not plugged in though. I don't know if that will make a difference.

[retiredcaps]

Re: Sony SMD-HS73

And yes, almost 14V out of a 12V line seems like it would be out of spec to me too.

Everyone has different troubleshooting techniques, but this is what I would do.

1) Have the upper 4 capacitors in your picture been replaced? I know you replaced some, but I can't tell from the picture if those 4 have been replaced?

2) In that same area, there are 2 inductors (marked with L on the PCB). They are covered in glue. You can remove the glue. With power off and LCD unplugged, the inductors should measure less than 1.0 ohms on your multimeter.

3) On the backside, there are 9 SMD resistors by the connector area. With power off and LCD unplugged, measure the resistance of each one. List the values and their measurements.

4) There are two, I believe, Schottky diodes mounted on the heat sink. With power on, put your black probe on a ground screw and red probe on the middle pin. Report both readings.

[PlainBill]

Re: Sony SMD-HS73

The legend on CN1 in the photo is a bit obscured, but if it says 12V, then 13.82V is pretty high? Was this measured with all the boards (logic and ccfl) hooked up?

I believe the 12V DC is for the inverter section.

That would be normal. Usually the 5V output is regulated, the 12V output floats depending on the load on the 5V supply. I'd expect the 12V output to be very close to 12V if the inverter was on, higher otherwise.

PlainBill

[torin3]

Re: Sony SMD-HS73

Everyone has different troubleshooting techniques, but this is what I would do.

1) Have the upper 4 capacitors in your picture been replaced? I know you replaced some, but I can't tell from the picture if those 4 have been replaced?

Yes, all 4 have been replaced. But after that photo was taken.

2) In that same area, there are 2 inductors (marked with L on the PCB). They are covered in glue. You can remove the glue. With power off and LCD unplugged, the inductors should measure less than 1.0 ohms on your multimeter.

Yes, both of them are less than 1.0 ohms.

3) On the backside, there are 9 SMD resistors by the connector area. With power off and LCD unplugged, measure the resistance of each one. List the values and their measurements.

I'm not quite sure about the values, some of them were hard to read. However, I do see that not all the ones marked 470 read the same. Also, I attached a closeup photo of that area.

R22 -470 - 47 ohms
R23 - 195 - 560 ohms
R24 - 202 - 664 ohms
R25 - 1095 - 933 ohms
R26 - 222 - 935 ohms
R27 - 470 - 23.5 ohms
R28 - 470 - 23.5 ohms
R42 - 3907 (3902?) - 1265 ohms
R44 - 272 - 2680 ohms

4) There are two, I believe, Schottky diodes mounted on the heat sink. With power on, put your black probe on a ground screw and red probe on the middle pin. Report both readings.

D1 is 5.05V
D12 is 13.81V

And thank you again for helping walk me through troubleshooting this.

[jetadm123]

Re: Sony SMD-HS73

Looks like you have good output voltages from both your power board and logic board regs.

May I suggest you try turning down the brightness to see if that affects the flickering at all.

Take your soldering iron and touch up the solder joints for the inverter transformer pins.

I see your logic about replacing the smd caps on the logic board. If others have had problems with those caps, then it might be a good idea to replace them.

[retiredcaps]

Re: Sony SMD-HS73

R22 -470 - 47 ohms
R23 - 195 - 560 ohms
R24 - 202 - 664 ohms
R25 - 1095 - 933 ohms
R26 - 222 - 935 ohms
R27 - 470 - 23.5 ohms
R28 - 470 - 23.5 ohms
R42 - 3907 (3902?) - 1265 ohms
R44 - 272 - 2680 ohms

R22 and R44 are definitely correct. The others readings are affected by other components in circuit. For now, let's assume they are all okay.

D1 is 5.05V
D12 is 13.81V

Hmm, I'm still confused with the 13.81V and the 12V DC connector reading, but let's assume that is correct and move on. I thought it would be closer to 12V DC at the connector area. At the diode area, I can see it being 13.81V DC.

Try measuring the secondaries. I believe what I circled in red and blue are the secondaries.

Put your mulitmeter on 2000 ohms. You should have one reading for red and one for blue. Report both.

[retiredcaps]

Re: Sony SMD-HS73

Also there is a 470uf 25V cap on the logic board I can replace as well.

Has this one been replaced as well?

[torin3]

Re: Sony SMD-HS73

May I suggest you try turning down the brightness to see if that affects the flickering at all.

I'll give that a try.

Take your soldering iron and touch up the solder joints for the inverter transformer pins.

Did that before my first post about this monitor.

Try measuring the secondaries. I believe what I circled in red and blue are the secondaries.

Put your mulitmeter on 2000 ohms. You should have one reading for red and one for blue. Report both.

Red 974
Blue 1003

[torin3]

Re: Sony SMD-HS73

Has this one been replaced as well?

Not yet. I'll do it now.

Edit: Crud, I'm out of 470uf 25V caps. I have 680uf 25V caps. Too much of step up in capacitance?

[jetadm123]

Re: Sony SMD-HS73

I tried checking T1 and T2. I think they are ok. Secondaries are about 1K ohm. And I get identical restances for the two units.

I also tried 1 lamp from another montior, in each of the sockets.

Still no change in behavior.

What points on T1 and T2 did you check when you first took these readings?