Soyo 24" stopped, help!

[freelander]

Re: Soyo 24" stopped, help!

Thanks...I'm pretty well versed in checking and changing capacitors but I just don't have much experience with the solid state devices so that throws me for a bit of a loop.

[retiredcaps]

Re: Soyo 24" stopped, help!

Can you guide me to the other item to check?

If the other item is measuring the caps for ESR, you have to unsolder all the caps and use an ESR meter to measure them. You can't measure it with your multimeter.

An ESR costs anywhere between $40 to $300. Replacing all your caps will cost less than $10.

[freelander]

Re: Soyo 24" stopped, help!

oops...I missed the picture

[freelander]

Re: Soyo 24" stopped, help!

Thanks Bill...I wasn't sure shich box you meant so I edited a picture of the board of the device that I tested (in circuit) and all pins are shorted to each other which would seem to me that it is blown. Can you guide me to the other item to check? Note that the 3 legged transistor on the other side of the heat sink also has all legs shorted to each other (in circuit).

[PlainBill]

Re: Soyo 24" stopped, help!

I picked up one of these monitors cheap and upon visual inspection of the capacitors, they look good but the very first fuse on incoming AC power is open. Is it fair to assume that this fuse would normally blow on a surge and all else may be good? I really don't want to fight with removing the heat sinks to get access to the components if I don't have to.

That is not a safe assumption. It is likely either the input rectifier or the main power FET is shorted. The input rectifier is the black rectangular 'box' attached to the heat sink just to the left of the power input socket in the first picture in this thread. You can check it for shorts from the bottom of the board.

If I were in your position I would replace every electrolytic cap in the power supply (including the 450 volt one) with new Panasonic FM or other high reliability brands. At a minimum, I would test the ESR on every cap. Again, if it became necessary to remove a heat sink, I would replace all the caps under that heat sink. This design is asinine.

PlainBill

[freelander]

Re: Soyo 24" stopped, help!

I picked up one of these monitors cheap and upon visual inspection of the capacitors, they look good but the very first fuse on incoming AC power is open. Is it fair to assume that this fuse would normally blow on a surge and all else may be good? I really don't want to fight with removing the heat sinks to get access to the components if I don't have to.

[PlainBill]

Re: Soyo 24" stopped, help!

Thats when my monitor started acting up after a week of being idle. This seems to be getting very complicated. By chance does anyone know what a lcd repair shop might charge to remedy this?

It depends on how honest they are. An honest shop would tell you up front to buy a new monitor; they couldn't get a replacement board. A less than honest shop would charge you $50 - $100 to look at it and tell you that they couldn't fix it. If you handed it to me I would ask a minimum of $30 for the labor, plus parts. At that, I'd be cheating myself.

All of that doesn't really matter. It shouldn't be too hard to figure out what to use to replace the diode. It's unlikely the inductor is bad, but if it is finding a replacement shouldn't be too hard. Soldering in the replacements is no more difficult than replacing the caps - easier as a matter of fact (unless you try holing it in place while soldering it.)

The first step is a picture of the top of the board so I can see if any component identifier is visible and a picture of the bottom of the board in that area to evaluate the solder. They don't have to be close-ups, the same scale as the pictures where I numbered the caps is fine.

PlainBill

[inaliz]

Re: Soyo 24" stopped, help!

Meaning they can put cheaper parts there. (Once it warms up it will mostly work fine, but cold-booting is the problem)

Thats when my monitor started acting up after a week of being idle. This seems to be getting very complicated. By chance does anyone know what a lcd repair shop might charge to remedy this?

[Krankshaft]

Re: Soyo 24" stopped, help!

Look what I found.

"Soyo Group filed for Chapter 7 bankruptcy with the United States District Court for the Central District of California, Riverside Division (case number 09-19355-RN), and ceased operations on May 5, 2009."

I guess in the end they stooped to rebrands good riddance I say.

I'd replace that charred diode look at it's neighbor if it's unreadable.

That burn mark over the zener is probably a part of that Topswitch PWM / FET IC circuit for the standby supply.

[Pyr0Beast]

Re: Soyo 24" stopped, help!

Soldering gun is too messy for that job. Buy a good soldering iron if you are planning to do more repairs. Good starts in the range of 100$+

Bad equipment will leave someone with no experience very frustrated. A pro can make good results with bad equipment, a newbie with bad equipment is a disaster.

You need good solder to do the job. Plumbing solder is for different purpose. While it does work it is not fit for any electronics. It is too thick and its flux is useless.

Buying cheap will not do the job. That money is better thrown away then.

//
This MAY be a difficult job. The ID10T who decided to put the caps under the heat sinks should have his hemorrhoids cauterized with a hot soldering iron. Maybe then he would be able to remove his head from his a**.//
It was done to reduce the ESR of the capacitors. Meaning they can put cheaper parts there. (Once it warms up it will mostly work fine, but cold-booting is the problem)

[Pyr0Beast]

Re: Soyo 24" stopped, help!

This diode (on top) is the part of the snubber circuit it seems. Its failure will lead to failure of the switching fet.

Heatsinks are not meant to have their fets/diodes unscrewed from there. You have to desolder everything. Much easier.

Main cap also failed which in turn heats the transformer like crazy.

[inaliz]

Re: Soyo 24" stopped, help!

Yes, underneath that is just solder I am saying.

[PlainBill]

Re: Soyo 24" stopped, help!

Underneath the mark you are talking about is just solder no diode and it does look rather bad compared to the rest.

The 'diode' I was referring to is the component on the top of the board. Notice how the discoloration is centered on it's leads?

PlainBill

[inaliz]

Re: Soyo 24" stopped, help!

Underneath the mark you are talking about is just solder no diode and it does look rather bad compared to the rest.

[PlainBill]

Re: Soyo 24" stopped, help!

Yes these concern me as well but don't know what I am supposed to do about it. Those 3 caps are the only ones really crammed in a horrible place under the heatsink. I would like to try to replace those 3 and see if it at least works.

Well, it pains me to say this, but that's not a totally bad idea. It would be a pain to have replaced all the caps then discover the monitor still doesn't work.

I do have an alternate suggestion, however. There are two areas that are discolored. You photographed the underside of the board for one of them - the one with less damage. Take a close look at the underside of the board for the other one. Does the solder look bad? Is the diode(?) shorted?

PlainBill

[inaliz]

Re: Soyo 24" stopped, help!

I am also concerned about the two overheated areas, in particular the one next to the large cap. That looks like it may have gotten hot enough to damage the component and weaken the solder on the underside of the board.

PlainBill

Yes these concern me as well but don't know what I am supposed to do about it. Those 3 caps are the only ones really crammed in a horrible place under the heatsink. I would like to try to replace those 3 and see if it at least works.

[PlainBill]

Re: Soyo 24" stopped, help!

So I have the time to work on my lcd today. I have removed the 3 bad caps, they were the 3 biggest ones underneath the heat shield. The rest of the caps on it look healthy. So should I replace these 3 or do I need to replace every cap on the entire psu? 17 in total including the tiny ones.

First of all, good job removing those heat sinks. I'd hate to have to do that. I'd really hate to have to do that twice.

I count 18 caps. See the attached pictures. Given the conditions those caps were working under, I have to ask this question: Would you prefer to replace all of them now, or replace three now and the rest in six months? Remember you will have to remove the heat sinks again if you have to replace the rest.

I am also concerned about the two overheated areas, in particular the one next to the large cap. That looks like it may have gotten hot enough to damage the component and weaken the solder on the underside of the board.

PlainBill

[inaliz]

Re: Soyo 24" stopped, help!

So I have the time to work on my lcd today. I have removed the 3 bad caps, they were the 3 biggest ones underneath the heat shield. The rest of the caps on it look healthy. So should I replace these 3 or do I need to replace every cap on the entire psu? 17 in total including the tiny ones.

[inaliz]

Re: Soyo 24" stopped, help!

Not necessarily fake. Putting caps under a heatsink like this is much like putting them in an oven. VERY bad design.

PlainBill

Also this monitor has been on heavy use since I got it april 2008. It has probably been off for less then 2 weeks total the entire time. I work from it and also a gamer.

In the process of removing and listing those caps will update asap, you guys rock!

[PlainBill]

Re: Soyo 24" stopped, help!

Bulged samXons? Are those fake?

Not necessarily fake. Putting caps under a heatsink like this is much like putting them in an oven. VERY bad design.

PlainBill