Sony SMD-HS73

[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.

[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.

[retiredcaps]

Re: Sony SMD-HS73

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

[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.

[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).

[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.

[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.

[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]

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.